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APPENDIX A

AUTOMATIC LINK ESTABLISHMENT SYSTEM

(SECOND GENERATION (2G) )

TABLE OF CONTENTS

PARAGRAPH PAGE

A.1 GENERAL. 50A.1.1 Scope. 50A.1.2 Applicability. 50A.2 APPLICABLE DOCUMENTS. 50A.2.1 General. 50A.2.2 Government documents. 50A.2.2.1 Specifications, standards, and handbooks. 50A.2.3 Non-Government publications. 51A.3 DEFINITIONS. 52A.3.1 Terms. 52A.3.2 Abbreviations and acronyms. 52A.3.3 Definitions of timing symbols. 54A.4 GENERAL REQUIREMENTS. 55A.4.1 ALE introduction. 55A.4.1.1 ALE addresses. 55A.4.1.2 Scanning. 55A.4.1.3 Calling. 56A.4.1.4 Channel evaluation. 56A.4.1.5 Channel quality display. 57A.4.2 System performance requirements. 57A.4.2.1 Scanning rate. 57A.4.2.1.1 Alternative Quick Call (AQC). 57A.4.2.1.2 Recommendation. 57A.4.2.2 Occupancy detection - not tested (NT). 57A.4.2.3 Linking probability. 58A.4.2.3.1 AQC-ALE linking probability. 60A.4.2.3.2 AQC-ALE linking performance. 60A.4.3 Required data structures. 60A.4.3.1 Channel memory. 60A.4.3.2 Self address memory. 61A.4.3.3 Other station table. 63A.4.3.3.1 Other station address storage. 63A.4.3.3.2 Link quality memory. 65A.4.3.3.3 Other station settings storage. 65A.4.3.4 Operating parameters. 65A.4.3.5 Message memory. 65A.4.4 ALE operational rules. 66A.4.5 Alternate Quick Call ALE (AQC-ALE) (NT). 66A.4.5.1 Introduction. 66A.4.5.2 General signaling strategies. 66TABLE OF CONTENTS(continued)PARAGRAPH PAGEA.4.5.3 Features supported by AQC-ALE. 67A.4.5.4 Features not provided by AQC-ALE. 68A.5. DETAILED REQUIREMENTS. 68A.5.1 ALE modem waveform. 68A.5.1.1 Introduction. 68A.5.1.2 Tones. 68A.5.1.3 Timing. 69A.5.1.4 Accuracy. 69A.5.2 Signal structure. 71A.5.2.1 Introduction. 71A.5.2.2 FEC. 71A.5.2.2.1 General. 71A.5.2.2.2 Golay coding. 71A.5.2.2.2.1 Encoding. 71A.5.2.2.2.2 Decoding. 71A.5.2.2.3 Interleaving and deinterleaving. 76A.5.2.2.4 Redundant words. 76A.5.2.3 Word structures. 76A.5.2.3.1 ALE word format. 76A.5.2.3.1.1 Structure. 81A.5.2.3.1.2 Word types. 81A.5.2.3.1.3 Preambles. 81A.5.2.3.2 Address words. 82A.5.2.3.2.1 TO. 82A.5.2.3.2.2 THIS IS (TIS). 82A.5.2.3.2.3 THIS WAS (TWAS). 82A.5.2.3.2.4 THRU. 82A.5.2.3.2.5 FROM. 83A.5.2.3.3 Message words. 83A.5.2.3.3.1 CMD. 83A.5.2.3.4 Extension words. 84A.5.2.3.4.1 DATA. 84A.5.2.3.4.2 REP. 84A.5.2.4 Addressing. 84A.5.2.4.1 Introduction. 84A.5.2.4.2 Basic 38 subset. 85A.5.2.4.3 Stuffing. 86A.5.2.4.4 Individual addresses. 86A.5.2.4.4.1 Basic size. 88A.5.2.4.4.2 Extended size. 88TABLE OF CONTENTS(continued)PARAGRAPH PAGEA.5.2.4.5 Net addresses. 90A.5.2.4.6 Group addresses. 90A.5.2.4.7 Allcall addresses. 90A.5.2.4.8 AnyCalls. 91A.5.2.4.9 Wildcards. 91A.5.2.4.10 Self addresses. 92A.5.2.4.11 Null address. 93A.5.2.4.12 In-link address. 93A.5.2.5 Frame structure. 93A.5.2.5.1 Calling cycle. 95A.5.2.5.2 Message section. 98A.5.2.5.3 Conclusion. 100A.5.2.5.4 Valid sequences. 103A.5.2.5.5 Basic frame structure examples. 103A.5.2.6 Synchronization. 107A.5.2.6.1 Transmit word phase. 107A.5.2.6.2 Receiver word sync. 108A.5.2.6.3 Synchronization criteria. 108A.5.3 Sounding. 109A.5.3.1 Introduction. 109A.5.3.2 Single channel. 110A.5.3.3 Multiple channels. 110A.5.3.4 Optional handshake. 115A.5.4 Channel selection. 117A.5.4.1 LQA. 117A.5.4.1.1 BER. 117A.5.4.1.2 SINAD. 118A.5.4.1.3 MP (optional). 118A.5.4.1.4 Operator display (optional). 118A.5.4.2 Current channel quality report (LQA CMD). 118A.5.4.2.1 BER field in LQA CMD. 118A.5.4.2.2 SINAD. 118A.5.4.2.3 MP. 118A.5.4.3 Historical LQA report. 120A.5.4.4 Local noise report CMD (optional). 120A.5.4.5 Single-station channel selection. 121A.5.4.5.1 Single-station channel selection for link establishment. 121A.5.4.5.2 Single-station channel selection for one-way broadcast. 123A.5.4.5.3 Single-station channel selection for listening. 123A.5.4.6 Multiple-station channel selection. 123TABLE OF CONTENTS(continued)PARAGRAPH PAGEA.5.4.7 Listen before transmit. 124A.5.4.7.1 Listen-before-transmit duration. 124A.5.4.7.2 Modulations to be detected. 124A.5.4.7.3 Listen before transmit override. 124A.5.5 Link establishment protocols. 124A.5.5.1 Manual operation. 124A.5.5.2 ALE. 125A.5.5.2.1 Timing. 125A.5.5.2.2 ALE states. 125A.5.5.2.3 ALE channel selection. 125A.5.5.2.3.1 Rejected channel. 126A.5.5.2.3.2 Busy channel. 126A.5.5.2.3.3 Exhausted channel list. 126A.5.5.2.4 End of frame detection. 126A.5.5.3 One-to-one calling. 129A.5.5.3.1 Sending an individual call. 129A.5.5.3.2 Receiving an individual call. 130A.5.5.3.3 Response. 131A.5.5.3.4 Acknowledgment. 132A.5.5.3.5 Link termination. 133A.5.5.3.5.1 Manual termination. 133A.5.5.3.5.2 Automatic termination. 133A.5.5.3.6 Collision detection. 134A.5.5.4 One-to-many calling. 134A.5.5.4.1 Slotted responses. 134A.5.5.4.1.1 Slotted response frames. 135A.5.5.4.1.2 Slot widths. 135A.5.5.4.1.3 Slot wait time formula. 135A.5.5.4.1.4 Slotted response example. 136A.5.5.4.2 Star net calling protocol. 136A.5.5.4.2.1 Star net call. 136A.5.5.4.2.2 Star net response. 137A.5.5.4.2.3 Star net acknowledgment. 137A.5.5.4.3 Star group calling protocol. 137A.5.5.4.3.1 Star group scanning call. 137A.5.5.4.3.2 Star group leading call. 138A.5.5.4.3.3 Star group call conclusion. 138A.5.5.4.3.4 Receiving a star group call. 138A.5.5.4.3.5 Star group slotted responses. 139A.5.5.4.3.6 Star group acknowledgment. 139TABLE OF CONTENTS(continued)PARAGRAPH PAGEA.5.5.4.3.7 Star group call example. 139A.5.5.4.3.8 Multiple self addresses in group call. 139A.5.5.4.4 Allcall protocol. 140A.5.5.4.5 AnyCall protocol. 141A.5.5.4.6 Wildcard calling protocol. 142A.5.6. ALE control functions (CMDs other than AMD, DTM, and DBM). 142A.5.6.1 CRC. 144A.5.6.2 Power control (optional). 146A.5.6.3 Channel related functions. 147A.5.6.3.1 Channel designation. 147A.5.6.3.2 Frequency designation. 148A.5.6.3.3 Full-duplex independent link establishment (optional). 149A.5.6.3.4 LQA polling (optional). 149A.5.6.3.5 LQA reporting (optional). 149A.5.6.3.6 LQA scan with linking (optional). 149A.5.6.3.7 Advanced LQA (optional). 149A.5.6.4 Time-related functions. 149A.5.6.4.1 Tune and wait. 149A.5.6.4.2 Scheduling commands. 150A.5.6.4.3 Time exchange word formats. 154A.5.6.4.3.1 Command words. 154A.5.6.4.3.2 Time Is command. 154A.5.6.4.3.3 Time Request command. 154A.5.6.4.3.4 Other encodings. 154A.5.6.4.4 Coarse time word. 154A.5.6.4.5 Authentication word. 155A.5.6.4.6 Time quality. 155A.5.6.5 Mode control functions (optional). 157A.5.6.5.1 Modem negotiation and handoff. 158A.5.6.5.1.1 Modem selection CMD. 158A.5.6.5.1.2 Modem negotiating. 158A.5.6.5.2 Crypto negotiation and handoff. 159A.5.6.6 Capabilities reporting functions. 160A.5.6.6.1 Version CMD (mandatory). 160A.5.6.6.2 Capabilities function. (mandatory). 161A.5.6.6.2.1 Capabilities query. 161A.5.6.6.2.2 Capabilities report CMD. 162A.5.6.6.2.3 Data format. 162A.5.6.7 Do not respond CMD. 165A.5.6.8 Position report (optional). 165TABLE OF CONTENTS(continued)PARAGRAPH PAGEA.5.6.9 User unique functions (UUFs). 165A.5.7 ALE message protocols. 167A.5.7.1 Overview. 167A.5.7.2 AMD mode (mandatory). 167A.5.7.2.1 Expanded 64-channel subset. 167A.5.7.2.2 AMD protocol. 168A.5.7.2.3 Maximum AMD message size. 169A.5.7.3 DTM mode. 169A.5.7.4 DBM mode. 181A.5.8 AQC (optional) (NT). 194A.5.8.1 Signaling structure (NT). 194A.5.8.1.1 AQC-ALE word structure (NT). 194A.5.8.1.1.1 Packed address (NT). 194A.5.8.1.1.2 Address differentiation flag (NT). 196A.5.8.1.2 Preambles (NT). 196A.5.8.1.2.1 TO (NT). 196A.5.8.1.2.2 THIS IS (TIS) (NT). 196A.5.8.1.2.3 THIS WAS (TWAS) (NT). 196A.5.8.1.2.4 PART2 (NT). 196A.5.8.1.2.5 INLINK (NT). 197A.5.8.1.2.6 COMMAND (NT). 197A.5.8.1.2.7 DATA (NT). 197A.5.8.1.2.8 REPEAT (NT). 197A.5.8.1.3 AQC-ALE address characteristics (NT). 197A.5.8.1.3.1 Address size (NT). 197A.5.8.1.3.2 Address character set (NT). 197A.5.8.1.3.3 Support of ISDN (option) (NT). 197A.5.8.1.3.4 Over-the-air address format (NT). 197A.5.8.1.4 Address formats by call type (NT). 197A.5.8.1.4.1 Unit addresses (NT). 197A.5.8.1.4.2 StarNet addresses (NT). 198A.5.8.1.4.3 Group addresses (NT). 198A.5.8.1.4.4 AllCall address (NT). 198A.5.8.1.4.5 AnyCall address (NT). 198A.5.8.1.5 Data exchange field (NT). 198A.5.8.1.5.1 DE(1) no data available (NT). 199A.5.8.1.5.2 DE(2) number of to's left in calling cycle (NT). 199A.5.8.1.5.3 DE(3) Inlink resource list (NT). 199A.5.8.1.5.4 DE(4) local noise report (NT). 200A.5.8.1.5.5 DE(5) LQA variation (NT). 201TABLE OF CONTENTS(continued)PARAGRAPH PAGEA.5.8.1.5.6 DE(6) LQA measurement (NT). 202A.5.8.1.5.7 DE(7) number of Tis/Twas left in sounding cycle (NT). 203A.5.8.1.5.8 DE(8) inlink data definition from INLINK (NT). 203A.5.8.1.5.9 DE(9) Inlink data definition from PART2 (NT). 204A.5.8.1.6 PSK tone sequence (optional) (NT). 205A.5.8.1.6.1 PSK tone sequence placement (NT). 205A.5.8.1.6.2 PSK tone sequence generation (NT). 205A.5.8.2 AQC-ALE frame structure and protocols (NT). 205A.5.8.2.1 Calling cycle (NT). 205A.5.8.2.2 Unit call structure (NT). 207A.5.8.2.3 Star net call structure (NT). 207A.5.8.2.4 AllCall frame formats (NT). 208A.5.8.2.5 AnyCall frame formats (NT). 209A.5.8.2.6 Sounding (NT). 210A.5.8.2.7 Inlink transactions (NT). 210A.5.8.2.7.1 Inlink transaction as an acknowledgement (NT). 211A.5.8.2.7.2 CRC for Inlink event sequences (NT). 211A.5.8.2.7.3 Use of address section (NT). 212A.5.8.2.7.4 Slotted responses in an Inlink state (NT). 212A.5.8.3 AQC-ALE orderwire functions (optional) (NT). 212A.5.8.3.1 Operator ACK/NAK transaction command section (optional) (NT). 212A.5.8.3.2 AQC-ALE control message section (optional) (NT). 213A.5.8.3.2.1 AMD dictionary message (NT). 214A.5.8.3.2.2 Channel definition (NT). 217A.5.8.3.2.3 Slot assignment (NT). 218A.5.8.3.2.4 List content of database (NT). 218A.5.8.3.2.5 List database activation time (NT). 218A.5.8.3.2.6 Set database activation time (NT). 218A.5.8.3.2.7 Define database content (NT). 219A.5.8.3.2.8 Database content listing (NT) 220A.5.8.4 AQC-ALE linking protection (NT). 220

TABLES

TABLE A-I. Occupancy detection probability (2G and 3G). 57TABLE A-II. Probability of linking. 59TABLE A-III. Channel memory example. 62TABLE A-IV. Self address memory example. 63TABLE A-V. ALE operational rules. 66TABLE A-VI. 2/3 majority vote decoding. 79TABLE A-VII. Majority word construction. 79TABLE OF CONTENTS(continued)PARAGRAPH PAGETABLE A-VIII. ALE word types (preambles). 81TABLE A-IX. Use of "@" utility symbol. 87TABLE A-X. Basic (38) address structures. 89TABLE A-XI. Use of "?" wildcard symbol. 92TABLE A-XII. Limits to frames. 103TABLE A-XIII. Basic BER values. 119TABLE A-XIV. Link quality analysis structure. 120TABLE A-XV. Timing. 127TABLE A-XVI. Summary of CMD functions. 143TABLE A-XVII. Cyclic redundancy check structure. 146TABLE A-XVIII. Power control CMD bits (KP1-3). 147TABLE A-XIX. Tune and wait structure. 151TABLE A-XX. Time values. 152TABLE A-XXI. Time-related CMD functions. 153TABLE A-XXII. Time quality. 156TABLE A-XXIII. Modem codes. 159TABLE A-XXIV. Crypto codes. 160TABLE A-XXV. Component selection. 161TABLE A-XXVI. Format selection. 161TABLE A-XXVII. Capabilities report data fields (ALE timing). 163TABLE A-XXVIII. Capabilities report data fields (mode settings). 163TABLE A-XXIX. Capabilities report data field (feature capabilities). 164TABLE A-XXX. User unique functions structure. 166TABLE A-XXXI. ALE message protocols. 167TABLE A-XXXII. DTM characteristics. 171TABLE A-XXXIII. DTM structure. 174TABLE A-XXXIV. DBM characteristics. 182TABLE A-XXXV. DBM structures. 188TABLE A-XXXVI. AQC address character ordinal value. 195TABLE A-XXXVII. AQC-ALE word types (and preambles). 196TABLE A-XXXVIII. Data exchange definitions. 198TABLE A-XXXIX. Inlink resource list. 200TABLE A-XL. Local noise report. 201TABLE A-XLI. Magnitude of minimum SNR from mean SNR. 202TABLE A-XLII. LQA scores. 203TABLE A-XLIII. Valid combinations of ACK-This and I'm Inlink. 204TABLE A-XLIV. DE(9) inlink transaction identifier. 205TABLE A-XLV. Scanning part duration using automated calculation. 206TABLE A-XLVI. Operator ACK/NAK command. 213TABLE A-XLVII. AQC-ALE control message section word sequences. 213TABLE OF CONTENTS(continued)PARAGRAPH PAGETABLE A-XLVIII. Lookup tables for packed AMD messages. 216TABLE A-IL. Adding spaces during AMD unpacking. 216

FIGURES

FIGURE A-1. Data link with ALE and FEC sublayers. 56FIGURE A-2. Occupancy detection test setup. 58FIGURE A-3. System performance measurements test setup. 58FIGURE A-4. Connectivity and LQA memory example. 64FIGURE A-5. ALE symbol library. 70FIGURE A-6. Generator matrix for (24, 12) extended Golay code. 72FIGURE A-7. Parity-check matrix for (24, 12) extended Golay code. 73FIGURE A-8. Golay word encoding example. 74FIGURE A-9. Golay FEC coding examples. 75FIGURE A-10. Word bit coding and interleaving. 77FIGURE A-11. Bit and word decoding. 78FIGURE A-12. ALE basic word structure. 80FIGURE A-13. Basic 38 subset (unshaded areas). 85FIGURE A-14. Valid word sequences. 94FIGURE A-15. Calling cycle sequence. 96FIGURE A-16. Message sequence. 99FIGURE A-17. Conclusion (terminator) sequences. 101FIGURE A-18. Valid word sequence (calling cycle section). 104FIGURE A-19. Valid word sequence (message section). 105FIGURE A-20. Valid word sequence (conclusion section). 106FIGURE A-21. Basic frame structure examples. 107FIGURE A-22. Basic sounding structure. 111FIGURE A-23. Call rejection scanning sounding protocol. 112FIGURE A-24. Call acceptance scanning sounding protocol. 113FIGURE A-25. Scanning sounding with optional handshake protocol. 116FIGURE A-26. Local noise report (optional). 121FIGURE A-27. LQA memory example. 122FIGURE A-28. Link establishment states. 125FIGURE A-29. Individual calls. 129FIGURE A-30. Response frame. 131FIGURE A-31. Acknowledgment frame. 132FIGURE A-32. Slotted responses. 135FIGURE A-33. 2G ALE slotted responses. 136FIGURE A-34. Net call. 136FIGURE A-35. Group call. 137FIGURE A-36. Power control CMD format. 147TABLE OF CONTENTS(continued)PARAGRAPH PAGEFIGURE A-37. Frequency select CMD format. 148FIGURE A-38. Time exchange CMD word. 155FIGURE A-39. Coarse time and authentication words. 156FIGURE A-40. Mode control CMD format. 157FIGURE A-41. Modem selection CMD format. 158FIGURE A-42. Crypto selection CMD format. 160FIGURE A-43. Version CMD format. 160FIGURE A-44. Capabilities query CMD format. 162FIGURE A-45. Capabilities report CMD and DATA format. 162FIGURE A-46. Expanded 64 ASCII subset (shown unshaded). 168FIGURE A-47. DTM structure example. 172FIGURE A-48. Data test message reconstruction (overlay). 177FIGURE A-49. Data test message structure and ARQ example. 184FIGURE A-50. DBM interleaver and deinterleaver. 185FIGURE A-51. DBM example. 186FIGURE A-52. AQC-ALE data exchange word. 195FIGURE A-53. Example of unit call format. 207FIGURE A-54. Example of StarNet format. 208FIGURE A-55. Example AllCall frame format. 209FIGURE A-56. Example AnyCall frame formats. 209FIGURE A-57. Example sounding frame format. 210FIGURE A-58. Example inlink transaction TRW sequences. 211FIGURE A-59. Generalized AQC-ALE control message format. 214FIGURE A-60. AQC-ALE dictionary lookup message. 215FIGURE A-61. Channel definition and meet-me function. 217FIGURE A-62. AQC-ALE slot assignment. 218FIGURE A-63. List content of database. 218FIGURE A-64. Set database activation time. 219FIGURE A-65. Define database content. 219

ANNEXES

ANNEX A. DEFINITIONS OF TIMING SYMBOLS 221ANNEX B. TIMING 224ANNEX C. SUMMARY OF ALE SIGNAL PARAMETERS 234

AUTOMATIC LINK ESTABLISHMENT SYSTEM

A.1 GENERAL.

A.1.1 Scope.

This appendix provides details of the prescribed waveform, signal structures, protocols, and performance requirements for the second generation (2G) automatic link establishment (ALE) system.

A.1.2 Applicability.

This appendix is a mandatory part of MIL-STD-188-141 whenever ALE is a requirement to be implemented into the high frequency (HF) radio system. The functional capability described herein includes automatic signaling, selective calling, automatic answering, and radio frequency (rf) scanning with link quality analysis (LQA). The capability for manual operation of the radio in order to conduct communications with existing, older generation, non-automated manual radios, shall not be impaired by implementation of these automated features.

A.2 APPLICABLE DOCUMENTS.

A.2.1 General.

The documents listed in this section are specified in A.3, A.4, and A.5 of this standard. This section does not include documents cited in other sections of this standard or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements documents cited in A.3, A.4, and A.5 of this standard, whether or not they are listed.

A.2.2 Government documents.

A.2.2.1 Specifications, standards, and handbooks.

The following specifications, standards, and handbooks form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those listed in the issue of the Department of Defense Index of Specifications and Standards (DODISS) and supplement thereto, cited in the solicitation.
STANDARDS
FEDERAL
Federal Information Processing Standards
FIPS PUB 1-1 Publication Code: for Information Interchange

FEDERAL STANDARDS
FED-STD-1003 Telecommunications: Synchronous Bit Orientation Data Link Control Procedures (Advanced Data Communications Control Procedures)
FED-STD-1037 Telecommunications: Glossary of Telecommunications Terms
DEPARTMENT OF DEFENSE
MIL-STD-188-110 Interoperability and Performance Standards for HF Data Modems

(Copies of Federal Information Processing Standards (FIPS) are available at Standardization Document Order Desk, 700 Robbins Avenue, Building #4, Section D, Philadelphia, PA 19111-5094. Non-Department of Defense (DoD) users must request copies of FIPS from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161-2171.)

A.2.3 Non-Government publications.

The following documents form a part of this appendix to the extent specified:
INTERNATIONAL STANDARDIZATION DOCUMENTS
North Atlantic Treaty Organization (NATO) Standardization Agreements (STANAGs)
STANAG 4285 Characteristics of 1200/2400/3600 bps Single Tone Modems for HF Radio Links
STANAG 4529 Characteristics of Single Tone Modulators/Demodulators for Maritime HF Radio Links with 1240 Hz Bandwidth
International Telecommunications Union (ITU),

Radio Regulations

ITU-R F.520-2 Recommendation for Fixed Service, use of High Frequency Ionospheric Channel Simulators

(Application for copies should be addressed to the General Secretariat, International Organization for Standardization (ISO) 1, Rue de Varembe, CH-1211 Geneva 20, Switzerland.)
Other Publications
NMSU-EE-CD-001 Wireless Network Waveform Samples

(Application for copies should be addressed to New Mexico State University, Klipsch School of Electrical and Computer Engineering, University Park, NM 88003, Attn: Dr. E. E. Johnson.)

(Non-Government standards and other publications are normally available from the organizations that prepare or distribute the documents. These documents also may be available in or through libraries or other informational services.)

A.3 DEFINITIONS.

A.3.1 Terms.

Definitions of terms used in this document shall be as specified in the current edition of
FED-STD-1037 except where inconsistent with the use in this standard. In addition, the following definitions are applicable for the purpose of this standard.

A.3.2 Abbreviations and acronyms.

The abbreviations and acronyms used in this document are defined below. Those listed in the current edition of FED-STD-1037 have been included for the convenience of the reader.
2G ALE second generation automatic link establishment
3G ALE second generation automatic link establishment
ACK acknowledge character
AQC Alternative Quick Call
AQC-ALE Alternative Quick Call Automatic Link Establishment
AGC automatic gain control
ALE automatic link establishment
AMD automatic message display
ARQ automatic repeat request
ASCII American Standard Code for Information Interchange
AWGNAdditive white gaussian noise
b/s bits per second
BCD binary coded decimal
BER bit error ratio
chps channels per second
CCIR International Radio Consultative Committee
CMD ALE preamble word COMMAND
CRC cyclic redundancy check
dBDecibel
dBw dB referred to 1 W (watt)
DBM data block message
DC data code
DCE data circuit-terminating equipment
DO design objective
DTE data terminal equipment
DTM data text message
e.g. for example
FCS frame check sequence
FEC forward error correction
FSK frequency shift keying
Hz hertz
HF high frequency
HFNC high frequency node controller
ID identification
IFF if and only if
ISDN Integrated Services Digital Network
kHz Kilohertz
LP linking protection
LQA link quality analysis
LSB (1) lower sideband

(2) least significant bit

ms millisecond
NATO North Atlantic Treaty Organization
ITU International Telecommunications Union
ISO Organization of Standardization
FIPS Federal Information Processing Standards
DODISS Department of Defense Index of Specifications and Standards
DoD Department of Defense
AQC Alternative Quick Call
MF medium frequency
MHz megahertz
MP multipath
MSB most significant bit
NAK negative-acknowledge character
NT Not Tested
PL probability of linking
PPM parts per million
rf radio frequency
REP ALE preamble word REPEAT
RX receive
s second
SCTY Security
SINAD signal-plus-noise-plus-distortion to noise-plus-distortion ratio
SN Slot Number
SNR signal to noise ratio
SPS symbols per second
SSB single-sideband [transmission]
TDMA time-division multiple access
TIS ALE preamble word THIS IS
TOD time of day
TWAS ALE preamble word THIS WAS
TX transmit
UI unique index
UUF user unique function
UUT units under test
WRTT wait for response and tune timeout
WS AQC-ALE Word Sync word

A.3.3 Definitions of timing symbols.

The abbreviations and acronyms used for timing symbols are contained in annex A to this appendix.

A.4 GENERAL REQUIREMENTS.

A.4.1 ALE introduction.

The techniques specified in this appendix employ a robust modem and forward error correction coding and constitutes a digital ALE data link. The exchange of such ALE words according to the specified protocols supports channel evaluation, selective calling, and passing data messages and constitute an ALE data link layer. (The ALE modem, radio, coupler, antenna, and so on constitute the corresponding physical layer.)

The ALE data link layer contains three sublayers, as shown in figure A-1: a lower sublayer concerned with error correction and detection (forward error correction [FEC] sublayer), an upper sublayer containing the ALE protocol (ALE sublayer), and a linking protection (LP) sublayer between. Within the FEC sublayer are redundancy and majority voting, interleaving, and Golay coding applied to the 24-bit ALE words which constitute the (FEC sublayer) service-data-unit, in terms of the Seven Layer Reference Model. The ALE sublayer specifies protocols for link establishment, data communication, and rudimentary LQA based on the capability of exchanging ALE words. The shaded area of figure A-1 indicates the contents of this appendix.

The following paragraphs specify the general requirements for ALE operation.

A.4.1.1 ALE addresses.

Stations designed to this appendix shall employ the addressing structure specified in A.5.2.4 to identify individual stations and collections of stations (nets and groups).

A.4.1.2 Scanning.

The radio system shall be capable of repeatedly scanning selected channels stored in memory (in the radio or controller) under either manual control or under the direction of any associated automated controller. The radio shall stop scanning and wait on the most recent channel upon the occurrence of any of the following selectable events:

The scanned channels should be selectable by groups (often called "scan lists") and also individually within the groups, to enable flexibility in channel and network scan management.



FIGURE A-1. Data link with ALE and FEC sublayers.

A.4.1.3 Calling.

Upon request by the operator or an external automated controller, the radio system shall execute the appropriate calling protocol specified in A.5.5.

A.4.1.4 Channel evaluation.

The radio system shall be capable of automatically transmitting ALE sounding transmissions in accordance with A.5.3, and shall automatically measure the signal quality of ALE receptions in accordance with A.5.4.1.

A.4.1.5 Channel quality display.

If an operator display is provided, the display shall have a uniform scale, 0-30 with 31 being unknown all based on signal-plus-noise-plus-distortion to noise-plus-distortion (SINAD).

A.4.2 System performance requirements.

Stations designed to this appendix shall demonstrate an overall system performance equal to or exceeding the following requirements.

A.4.2.1 Scanning rate.

Stations designed to this appendix shall incorporate selectable scan rates of two and five channels per second, and may also incorporate other scan rates (design objective (DO): 10 channels per second).

A.4.2.1.1 Alternative Quick Call (AQC) (NT).

In the optional AQC-ALE protocol, the system shall be capable of variable dwell rates while scanning such that traffic can be detected in accordance with table A-II Probability of Linking.

A.4.2.1.2 Recommendation.

Radios equipped with the optional AQC-ALE shall provide scanning at scan rates of two channels per second or five channels per second for backward compatibility to non-AQC-ALE networks.

A.4.2.2 Occupancy detection - not tested (NT).

Stations designed to this appendix shall achieve at least the following probability of detecting the specified waveforms (See A.5.4.7) under the indicated conditions, with false alarm rates of no more than 1 percent. The channel simulator shall provide additive white gaussian noise (AWGN) without fading or multipath (MP). See table A-I.

TABLE A-I. Occupancy detection probability (2G and 3G).
WaveformSNR (dB in 3 kHz) Dwell Time (s) Detection Prob
ALE0 2.00.80
6 2.00.99
SSB Voice6 2.00.80
9 2.00.99
MIL-STD-188-1100 2.00.80
(Serial Tone PSK)6 2.00.99
STANAG 45290 2.00.80
6 2.00.99
STANAG 42850 2.00.80
6 2.00.99

Baseband Signal Source
Baseband HF Channel Simulator Rx Audio
ALE Controller UUT

NOTES:
  1. The single side-band (SSB) voice test signal shall be taken from The Wireless Network Samples NMSU­EE­CD­021.
  2. The PSK test signal shall be taken from The Wireless Network Samples NMSU­EE­CD­021.

FIGURE A-2. Occupancy detection test setup.


FIGURE A-3. System performance measurements test setup.

A.4.2.3 Linking probability.

Linking attempts made with a test setup configured as shown in figure A-3, using the specified ALE signal created in accordance with this appendix, shall produce a probability of linking as shown in table A-II.

TABLE A-II. Probability of linking.
Signal-to-noise ratio (dB in 3 kHz)
Probability of

Linking (Pl)

Gaussian Noise Channel Modified

CCIR Good Channel

Modified

CCIR Poor Channel

³ 25%

³ 50%

³ 85%

³ 95%

-2.5

-1.5

-0.5

0.0

+0.5

+2.5

+5.5

+8.5

+1.0

+3.0

+6.0

+11.0

Multipath (millisecond)

Doppler spread (Hertz)

0.0

0.0

0.52

0.10

2.2

1.0

The receive audio input to the ALE controller shall be used to simulate the three channel conditions. The modified International Radio Consultative Committee (CCIR) good channel shall be characterized as having 0.52 millisecond (ms) (modified from 0.50ms) MP delay and a fading (two sigma) bandwidth of 0.1 hertz (Hz). The modified CCIR poor channel, normally characterized as consisting of a circuit having 2.0 ms MP delay with a fading (two sigma) bandwidth of 1.0 Hz, shall be modified to have 2.2 ms MP delay and a fading (two sigma) bandwidth of 1.0 Hz. Doppler shifts of +60 Hz shall produce no more than a 1.0 decibel (dB) performance degradation from the requirements of table A-II for the modified CCIR good and poor channels.

NOTE: This modification is necessary due to the fact that the constant 2-ms MP delay (an unrealistic fixed condition) of the CCIR poor channel results in a constant nulling of certain tones of the ALE tone library. Other tone libraries would also have some particular MP value, which would result in continuous tone cancellation during simulator testing.

Each of the signal-to-noise (SNR) ratio values shall be measured in a nominal 3-kiloHertz (kHz) bandwidth. Performance tests of this capability shall be conducted in accordance with ITU-R F.520-2 Use of High Frequency Ionospheric Channel Simulators employing the C.C. Watterson Model. This test shall use the individual scanning calling protocol described in A.5.5.3. The time for performance of each link attempt shall be measured from the initiation of the calling transmission until the successful establishment of the link. Performance testing shall include the following additional criteria:

a. The protocol used shall be the individual scanning calling protocol with only TO and TIS preambles.

b. Addresses used shall be alphanumeric, one word (three characters) in length from the 38-character basic American Standard Code for Information Interchange (ASCII) subset.

c. Units under test (UUTs) shall be scanning 10 channels at two channels per second, and repeated at five channels per seconds.

d. Call initiation shall be performed with the UUT transmitter stopped and tuned to the calling frequency.

e. Maximum time from call initiation (measured from the start of UUT rf transmission -- not from activation of the ALE protocol) to link establishment shall not exceed 14.000 seconds, plus simulator delay time. The call shall not exceed 23 redundent words, the response three redundent words and the acknowledgment three redundent words. (See A.5.2.2.4 and Annex A).

NOTE: Performance at the higher scan rates shall also meet the foregoing requirements and shall meet or exceed the probability of linking as shown in table A-II.

A.4.2.3.1 AQC-ALE linking probability.

When the optional AQC-ALE protocol is implemented, the probability of linking shall conform to table A-II with the following additional criteria:

a. The protocol used shall be quick AQC individual calling protocol with no message passing.

b. Addresses shall be one to six characters in the 38-character basic ASCII subset.

c. Units being called shall be scanning 10 channels.

d. Call initiation shall be performed with the UUT transmitter stopped and tuned to the calling frequency.

e. The initial call probe shall not exceed 10 Trw, the call response shall not exceed 4Trw, and the acknowledgment shall not exceed 2 Trw.

A.4.2.3.2 AQC-ALE linking performance.

AQC-ALE linking performance shall not be degraded in LP level 1 or 2. Scan rates of two or five channels per second may degrade performance because insufficient redundent words are emitted during the call probe.

A.4.3 Required data structures.

A.4.3.1 Channel memory.

The equipment shall be capable of storing, retrieving, and employing at least 100 different sets of information concerning channel data to include receive and transmit frequencies with associated mode information. See table A-III. The channel data storage shall be nonvolatile.

The mode information normally includes:

Any channel (a) shall be capable of being recalled manually or under the direction of any associated automated controller, and (b) shall be capable of having its information altered after recall without affecting the original stored information settings.

A.4.3.2 Self address memory.

The radio shall be capable of storing, retrieving, and employing at least 20 different sets of information concerning self addressing. The self-address information storage shall be nonvolatile. These sets of information include self (its own personal) address(es), valid channels which are associated for use, and net addressing. Net addressing information shall include (for each "net member" self address, as necessary) the net address and the associated slot wait time (in multiples of Tw). See table A-IV and A.5.5.4.1. The slot wait time values are Tswt(slot number (SN)) from the formula, Tswt (SN) = Tsw x SN . Stations called by their net call address shall respond with their associated self (net member) address with the specified delay (Tswt(SN)). For example, the call is "GUY," thus the response is "BEN." Stations called individually by one of their self addresses (even if a net member address) shall respond immediately and with that address, as specified in the individual scanning calling protocol. Stations called by one of their self addresses (even if a net member address) within a group call shall respond in the derived slot, and with that address, as specified in the star group scanning protocol. If a station is called by one of its net addresses and has no associated net member address, it shall pause and listen but shall not respond (unless subsequently called separately with an available self or net member address), but shall enter the linked state.

TABLE A-III. Channel memory example.


TABLE A-IV. Self address memory example.


Index
Self (or Net Member) Address
Net

Address

Tswt(SN)=

Slot Wait

Time (Tw)

(4)

Valid

Channels


Example

Comments

SA1SAM ---- Allsimple individual address, 1-word, all channels
SA2BOBBIE ---- C1,2,3simple individual address, 2-word, limited channels
SA3JIM ---- C7simple individual address, 1-word, single channel
SA4BEN GUY14 Allnet and individual addresses, 1-word, all channels, preset slot unit time (slot 1)
SA5CLAUDETTE GAL80 C3-C7net and 3-word individual addresses, limited channels, preset slot wait-time (slot 4)
SA6JOE PEOPLE17 C1-C92-word net and 1-word individual addresses, limited channels preset slot wait-time
×× ×× ×
×× ×× ×
×× ×× ×
SA20-- PARTY-- C5-C122-word net only address, therefore receive only if called
NOTES:
  1. The self address number "SA#" index is included for clarity. Indexes may be useful for efficient memory management.
  2. If a net address is associated with a self address, the self address should be referred to as a "net member" address.
  3. Addresses and values shown for example only.
  4. Valid channels are the channels on which this address is planned, or permitted, to be used.

A.4.3.3 Other station table.

The radio shall be capable of storing, retrieving, and employing at least 100 different sets of information concerning the addresses of other stations and nets, channel quality data to those stations and nets (measurements or predictions), and equipment settings specific to links with each station or net.

DO: any excess capacity which is not programmed with preplanned other station information should be automatically filled with any addresses heard on any of the scanned or monitored channels. When the excess capacity is filled, it should be kept current by replacing the oldest heard addresses with the latest ones heard. This information should be used for call initiation to stations (if needed), and for activity evaluation.

A.4.3.3.1 Other station address storage.

Individual station addresses shall be stored in distinct table entries, and shall be associated with a specific wait for reply time (Twr) if not the default value. Net information shall include own net and net member associations, relative slot sequences, and own net wait for reply times (Twrn) for use when calling. See figure A-4. The storage for addresses and settings shall be nonvolatile.



FIGURE A-4. Connectivity and LQA memory example.

A.4.3.3.2 Link quality memory.

The equipment shall be capable of storing, retrieving, and employing at least 4000 (DO: 10,000) sets of connectivity and LQA information associated with the channels and the other addresses in an LQA memory. The connectivity and LQA information storage shall be retained in memory for not less than one hour during power down or loss of primary power. The information in each address/channel "cell" shall include as a minimum, bilateral SINAD values of (a) the signals received at the station, and (b) the station's signals received at, and reported by, the other station. It shall also include either an indicator of the age of the information (for discounting old data), or an algorithm for automatically reducing the weight of data with time, to compensate for changing propagation conditions. (DO: the cells of the LQA memory should also include bilateral bit-error ratio (BER) and bilateral MP information derived by suitably equipped units.) The information within the LQA memory shall be used to select channels and manage networks as stated in this document. See figure A-4.

A.4.3.3.3 Other station settings storage.

DO: Equipment settings for use in linking with specific stations or nets should be stored in nonvolatile memory. Such settings may include antenna selection and azimuth, channels authorized for that station or net, power limits for the relevant net, and so on.

A.4.3.4 Operating parameters.

The following ALE operating parameters shall be programmable by the operator or an external automated controller. Complete definitions of the parameters are provided in Appendix H.
ScanRateRequestLQAOtherAddr LqaStatus
MaxScanChanAutoPowerAdj OtherAddrStatusLqaAge
MaxTuneTimeSelfAddrTable OtherAddrNetMembersLqaMultipath
TurnAroundTimeSelfAddrEntry OtherAddrValidChannelsLqaSINAD
ActivityTimeoutSelfAddr OtherAddrAntLqaBER
ListenTimeSelfAddrStatus OtherAddrAntAzimuthScanSet
AcceptAnyCallNetAddr OtherAddrPowerConnectionTable
AcceptAllcallSlotWaitTime LqaMatrixConnectionEntry
AcceptAMDSelfAddrValidChannels LqaEntryConnectedAddr
AcceptDTMOtherAddrTable LqaAddrConnectionStatus
AcceptDBMOtherAddrEntry LqaChannel

A.4.3.5 Message memory.

Storage for preprogrammed, operator entered, and incoming messages shall be provided in the equipment. This storage shall be retained in memory for not less than one hour during power down or loss of primary power. Storage for at least 12 messages (DO: 100 messages), and a total capacity of at least 1000 characters (DO: 10,000 characters) shall be provided.

A.4.4 ALE operational rules.

The ALE system shall incorporate the basic operational rules listed in table A-V. Some of these rules may not be applicable in certain applications. For example, "always listening" is not possible while transmitting with a transceiver or when using a common antenna with a separate transmitter and receiver.

TABLE A-V. ALE operational rules.
1) Independent ALE receive capability (in parallel with other modems and simular audio receivers) (critical).
2) Always listening (for ALE signals) (critical).
3) Always will respond (unless deliberately inhibited).
4) Always scanning (if not otherwise in use).
5) Will not interfere with active channel carrying detectable traffic in accordance with table A-I (unless this listen call function is overriden by the operator or other controller).
6) Always will exchange LQA with other stations when requested (unless inhibited), and always measures the signal quality of others.
7) Will respond in the appropriate time slot to calls requiring slotted responses.
8) Always seek (unless inhibited) and maintain track of their connectivities with others.
9) Linking ALE stations employ highest mutual level of capability.
10) Minimize transmit and receive time on channel.
11) Automatically minimize power used (if capable).

NOTE : Listed in order of precedence.

A.4.5 Alternate Quick Call ALE (AQC-ALE) (NT).

A.4.5.1 Introduction.

This feature may be implemented in addition to the basic ALE functionality described in this appendix. The AQC-ALE provides a link establishment technique that requires significantly less time to link than the baseline ALE system. This is accomplished by some additional technology and trading-off some of the lesser used functions of the baseline system, for a faster linking process. The AQC-ALE shall always be listening for the baseline ALE call and shall automatically respond and operate in that mode when called.

A.4.5.2 General signaling strategies.

The AQC-ALE format employs the following characteristics:

a. Packs three address characters (21 bits) into a 16-bit value

b. Addresses are reduced from a maximum of 15 characters to 6 characters

c. Six (6) address characters are sent in every transaction

d. Replaces two seldom used preambles as follows:

e. Isolates station addresses from message portion of the signaling structure:

f. Easy separation of second generation basic ALE and AQC-ALE protocols:

g. Provides at least eight information bits per transmission

A.4.5.3 Features supported by AQC-ALE.

The following basic ALE features are fully implemented using the AQC-ALE protocol.

NOTE: A station operating in AQC-ALE can respond to any call type, but a station equipped with only second generation basic ALE will not respond to AQC-ALE protocol forms.

a. Linking protection levels 0, 1, 2, 3

b. Unit calls

c. Star Net calls

d. Allcalls

e. AnyCalls

f. LQA Exchange as part of the call handshake

g. Supports Orderwire and Relay features while in a link:

h. Sound:

A.4.5.4 Features not provided by AQC-ALE.

a. Group call. As an alternative, a controller can use the calling protocol to add on additional members. Behavior of the system is more akin to setting up a call and then conferencing in a third party.

b. AMD, DTM, DBM are not provided during link set up. Primary focus of AQC-ALE is to establish a link between two or more stations as rapidly as possible. Once linked, information can be exchanged in the most efficient manner as is common between stations.

c. Early identification of transmitter's address during orderwire traffic or additional addressing identification for relay addresses. The need for this is eliminated because the call setup is significantly reduced. Orderwire messages are not allowed during the call setup.

A.5. DETAILED REQUIREMENTS.

A.5.1 ALE modem waveform.

A.5.1.1 Introduction.

The ALE waveform is designed to pass through the audio passband of standard SSB radio equipment. This waveform shall provide for a robust, low-speed, digital modem capability used for multiple purposes to include selective calling and data transmission. This section defines the waveform including the tones, their meanings, the timing and rates, and their accuracy.

A.5.1.2 Tones.

The waveform shall be an 8-ary frequency shift-keying (FSK) modulation with eight orthogonal tones, one tone (or symbol) at a time. Each tone shall represent three bits of data as follows (least significant bit (LSB) to the right):

The transmitted bits shall be encoded and interleaved data bits constituting a word, as described in paragraphs A.5.2.2 and A.5.2.3. The transitions between tones shall be phase continuous and shall be at waveform maxima or minima (slope zero).

A.5.1.3 Timing.

The tones shall be transmitted at a rate of 125 tones (symbols) per second, with a resultant period of 8 ms per tone. Figure A-5 shows the frequency and time relationships. The transmitted bit rate shall be 375 bits per second (b/s). The transitions between adjacent redundant (tripled) transmitted words shall coincide with the transitions between tones, resulting in an integral
49 symbols (or tones) per redundant (tripled) word. The resultant single word period (Tw) shall be 130.66... ms (or 16.33... symbols), and the triple word (basic redundant format) period (3 Tw) shall be 392 ms.

A.5.1.4 Accuracy.

At baseband audio, the generated tones shall be within +1.0 Hz. At rf, all transmitted tones shall be within the range of 2.0 dB in amplitude. Transmitted symbol timing, and therefore, the bit and word rates shall be within ten parts per million.

FIGURE A-5. ALE symbol library.

A.5.2 Signal structure.

A.5.2.1 Introduction.

This section provides definition of the ALE signal structure. Included are: forward error correction, word structure, addressing, frame structure, and synchronization. Also described in this section are: addressing, signal quality analysis, and the functions of the standard word preambles associated with the signal structure.

A.5.2.2 FEC.

A.5.2.2.1 General.

The effective performance of stations, while communicating over adverse rf channels, relies on the combined use of forward error correction, interleaving, and redundancy. These functions shall be performed within the transmit encoder and receive decoder.

A.5.2.2.2 Golay coding.

  • The Golay (24, 12, 3) FEC code is prescribed for this standard. The FEC code generator polynomial shall be:
  • g(x) = x11 + x9 + x7 + x6 + x5 + x + 1

    The generator matrix G, derived from g(x), shall contain an identity matrix I12 and a parity matrix P as shown in figure A-6. The corresponding parity check matrix H shall contain a transposed matrix pT and an identity matrix I12 as shown in figure A-7.

    A.5.2.2.2.1 Encoding.
  • Encoding shall use the fundamental formula x = uG, where the code word x shall be derived from the data word u and the generator matrix G. Encoding is performed using the G matrix by summing (modulo-2) the rows of G for which the corresponding information bit is a "1." See figures A-6, A-8, and A-9a.
  • A.5.2.2.2.2 Decoding.
  • Decoding will implement the equation
  • s = y HT

    where y = x + e is a received vector which is the modulo-2 sum of a code word x and an error vector e, s is a vector of "n - k" bits called the syndrome. See figure A-9. See figure A-7 for the value of H. Each correctable/detectable error vector e results in a unique vector s. Because of this, s is computed according to the equation above and is used to index a look-up of the corresponding e, which is then added modulo-2 to y to give the original code word x. Flags are set according to the number of errors being corrected. The uses of the flags are described in A.5.2.6. If s is not equal to 0 and e contains more ones than the number of errors being corrected by decoding mode, a detected error is indicated and the appropriate flag is set.

    I12 P
    100000 000000: 101011100 011
    010000 000000: 111110010 010
    001000 000000: 110100101 011
    000100 000000: 110001110 110
    000010 000000: 110011011 001
    000001 000000: 011001101 101
    G=000000 100000: 001100110 111
    000000 010000: 101101111 000
    000000 001000: 010110111 100
    000000 000100: 001011011 110
    000000 000010: 101110001 101
    000000 000001: 010111000 111

    FIGURE A-6. Generator matrix for (24, 12) extended Golay code.
    PT I12

    111110 010010: 100000000 000
    011111 001001: 010000000 000
    110001 110110: 001000000 000
    011000 111011: 000100000 000
    110010 001111: 000010000 000
    H=100111 010101: 000001000 000
    101101 111000: 000000100 000
    010110 111100: 000000010 000
    001011 011110: 000000001 000
    000101 101111: 000000000 100
    111100 100101: 000000000 010
    101011 100011: 000000000 001

    FIGURE A-7. Parity-check matrix for (24, 12) extended Golay code.

    12 Bits To Encode
    1
    1
    0
    1
    0
    0
    0
    1
    0
    1
    0
    1
    Bit Numbers
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    1
    100
    000
    000
    000
    101
    011
    100
    011
    2
    010
    000
    000
    000
    111
    110
    010
    010
    4
    000
    100
    000
    000
    110
    001
    110
    110
    8
    000
    000
    010
    000
    101
    101
    111
    000
    10
    000
    000
    000
    100
    001
    011
    011
    110
    12
    000
    000
    000
    001
    010
    0111
    000
    011
    110
    100
    010
    101
    010
    101
    100
    110
    ENCODED DATA BITS* W1…W12 (OR W13…W24)
    GOLAY CHECK BITS G1…G12 (OR G13…G24)
    24 BITS CODE WORD TO SEND
    *See note 2

    NOTES:

    1. The "bits" to be encoded determine which rows of the "G" generator matrix are to be "modulo-2" summed. In this example, bits 1, 2, 4, 8, 10, and 12 are "1," so row 1, 2, 4, 8, 10, and 12 are summed.
    2. Because this is a "systematic" code, the original 12 data bits also appear in the output encoded 24 bits.

    FIGURE A-8. Golay word encoding example.


    FIGURE A-9. Golay FEC coding examples.

    A.5.2.2.3 Interleaving and deinterleaving.

  • The basic word bits W1 (most significant bit (MSB)) through W24 (LSB), and resultant Golay FEC bits G1 through G24 (with G13 through G24 inverted), shall be interleaved, before transmission using the pattern shown in figure A-10. The 48 interleaved bits plus a 49th stuff bit S49, (value = 0) shall constitute a transmitted word and they shall be transmitted A1, B1, A2, B2... A24, B24, S49 using 16-1/3 symbols (tones) per word (Tw) as described in A.5.1.3. At the receiver, and after 2/3 voting (see A.5.2.2.4), the first 48 received bits of the majority word (including remaining errors) shall be deinterleaved as shown in figure A-10 and then Golay FEC decoded to produce a correct(ed) 24-bit basic word (or an uncorrected error flag). The 49th stuff bit (S49) is ignored.
  • A.5.2.2.4 Redundant words.

    Each of the transmitted 49-bit (or 16-1/3 symbol) (Tw) words shall be sent redundantly (times 3) to reduce the effects of fading, interference, and noise. An individual (or net) routing word (TO...), used for calling a scanning (multichannel) station (or net), shall be sent redundantly as long as required in the scan call (Tsc) to ensure receipt, as described in A.5.5.2. However, when the call is a non-net call to multiple scanning stations (a group call, using THRU and REPEAT (REP) alternately), the first individual routing word (THRU) and all the subsequent individual routing words (REP, THRU, REP,...) shall be sent three adjacent times (Trw). These triple words for the individual stations shall be rotated in group sequence as described in A.5.5.3. See figure A-11. At bit time intervals (approximately Tw/49), the receiver shall examine the present bit and past bit stream and perform a 2/3 majority vote, on a bit-by-bit basis, over a span of three words. See tables A-VI and A-VII. The resultant 48 (ignoring the 49th bit) most recent majority bits constitute the latest majority word and shall be delivered to the deinterleaver and FEC decoder. In addition, the number of unanimous votes of the 48 possible votes associated with this majority word are temporarily retained for use as described in A.5.2.6.

    A.5.2.3 Word structures.

    A.5.2.3.1 ALE word format.

    The basic ALE word shall consist of 24 bits of information, designated W1 (MSB) through W24 (LSB). The bits shall be designated as shown in figure A-12.



    FIGURE A-10. Word bit coding and interleaving.


    FIGURE A-11. Bit and word decoding.

    TABLE A-VI. 2/3 Majority vote decoding.

    Received Bit R

    Received Time
    Eight Possible Bit Combinations
    R (n) (now)T 00 00 11 11
    R(n-49) (Tw old) T-130.66... ms0 01 10 01 1
    R(n-98) (2 Tw old) T-261.33... ms0 10 10 10 1
    Resultant majority bit M: 0 00 10 11 1
    Possible error flag: 01 11 11 10
    0 = error unlikely

    1 = error likely

    TABLE A-VII. Majority word construction.

    Relative Time

    Received Bits R (Time) for 2/3 Voting
    Majority Words Bit M Used as Decoder Bits
    Stuff bits

    Recent (LSB)







    Older (MSB)

    R(n)

    R(n-1)

    R(n-2)

    R(n-3)

    R(n-4)

    R(n-46)

    R(n-47)

    R(n-48)

    R(n-49)

    R(n-50)

    R(n-51)

    R(n-52)

    R(n-53)

    R(n-95)

    R(n-96)

    R(n-97)

    R(n-98)

    R(n-99)

    R(n-100)

    R(n-101)

    R(n-102)

    R(n-144)

    R(n-145)

    R(n-146)

    M(n)

    M(n-1)

    M(n-2)

    M(n-3)

    M(n-4)

    M(n-46)

    M(n-47)

    M(n-48)

    S49 ignored

    B24 (LSB)

    A24

    B23

    A23

    A2

    B1

    A1 (MSB)


    NOTES:
    1. "n" indicates present bit time
    2. "n-m" indicates bit received at "m" bit times earlier



    FIGURE A-12. ALE basic word structure.
    A.5.2.3.1.1 Structure.
  • The word shall be divided into two parts: a 3-bit preamble and a 21-bit data field (which often contains three 7-bit characters). The MSB for all parts, and the word, is to the left in figure A-12 and is sent earliest. Before transmission, the word shall be divided into two 12-bit halves (Golay code A and B in figure A-10) for FEC encoding as described in 5.2.2.
  • The optional AQC-ALE word packs the address data. Details of this can be found in A.5.8.1.1, AQC-ALE Address Word Structure.
  • A.5.2.3.1.2 Word types.

    The leading three bits, W1 through W3, are designated preamble bits P3 through P1, respectively. These preamble bits shall be used to identify one of eight possible word types.

    A.5.2.3.1.3 Preambles.
  • The word types (and preambles) shall be as shown in table A-VIII and as described herein.
  • Optional AQC-ALE preambles are defined in A.5.8.1.2.

    TABLE A-VIII. ALE word types (preambles).
    Word

    Type

    Code Bits FunctionsSignificance
    THRU 001multiple (and indirect routing present multiple direct destinations for group calls (and future indirect relays, reserved)
    TO 010direct routing present direct destination for individual and net calls
    CMD 110orderwire control and status ALE system-wide station (and operator) orderwire for coordination, control, status, and special functions
    FROM 100identification (and indirect routing) identification of present transmitter without termination (and past originator and relayers, reserved)
    TIS 101terminator and identification continuing identification of present transmitter, signal terminations, protocol continuation
    TWAS 011terminator and identification quitting identification of present transmitter, signal and protocol termination
    DATA 000extension and information extension of data field of the previous ALE work, or information defined by the previous CMD
    REP 111duplication and information duplication of the previous preamble, or information defined by the previous CMD
    P3

    MSB

    W1

    P2

    W2

    P1

    LSB

    W3

    A.5.2.3.2 Address words.

    A.5.2.3.2.1 TO.
  • The TO word (010) shall be used as a routing designator which shall indicate the address of the present destination station(s) which is (are) to directly receive the call. TO shall be used in the individual call protocols for single stations and in the net call protocols for multiple net-member stations which are called using a single net address. The TO word itself shall contain the first three characters of an address. For extended addresses, the additional address words (and characters) shall be contained in alternating DATA and REP words, which shall immediately follow. The sequence shall be TO, DATA, REP, DATA, and REP, and shall be only long enough to contain the address, up to a maximum capacity of five address words (15 characters).
  • A.5.2.3.2.2 THIS IS (TIS).

    The TIS word (101) shall be used as a routing designator which shall indicate the address of the present calling (or sounding) station which is directly transmitting the call (or sound). Except for the use of TWAS, TIS shall be used in all ALE protocols to terminate the ALE frame and transmission. It shall indicate the continuation of the protocol or handshake, and shall direct, request, or invite (depending on the specific protocol) responses or acknowledgments from other called or receiving stations. The TIS shall be used to designate the call acceptance sound. The TIS word itself shall contain the first three characters of the calling stations address. For extended addresses, the additional address words (and characters) shall be contained in alternating DATA and REP words which shall immediately follow, exactly as described for whole addresses using the TO word and sequence. The entire address (and the required portion of the TIS, DATA, REP, DATA, REP sequence, as necessary) shall be used only in the conclusion section of the ALE frame (or shall constitute an entire sound). TWAS shall not be used in the same frame as TIS, as they are mutually exclusive.

    A.5.2.3.2.3 THIS WAS (TWAS).
  • The TWAS word (011) shall be used as a routing designator exactly as the TIS, with the following variations. It shall indicate the termination of the ALE protocol or handshake, and shall reject, discourage, or not invite (depending on the specific protocol) responses or acknowledgments from other called or receiving stations. The TWAS shall be used to designate the call rejection sound. TIS shall not be used in the same frame as TWAS, as they are mutually exclusive.
  • A.5.2.3.2.4 THRU.

    The THRU word (001) shall be used in the scanning call section of the calling cycle only with group call protocols. The THRU word shall be used alternately with REP, as routing designators, to indicate the address first word of stations that are to be directly called. Each address first word shall be limited to one basic address word (three characters) in length. A maximum of five different address first words shall be permitted in a group call. The sequence shall only be alternations of THRU, REP. The THRU shall not be used for extended addresses, as it will not be used within the leading call section of the calling cycle. When the leading call starts in the group call, the entire group of called stations shall be called with their whole addresses, which shall be sent using the TO preambles and structures, as described in A.5.2.3.2.1.

    NOTE: 1. The THRU word is also reserved for future implementation of indirect and relay protocols, in which cases it may be used elsewhere in the ALE frame and with whole addresses and other information. Stations designed in compliance with this nonrelay standard should ignore calls to them which employ their address in a THRU word in other than the scanning call.

    NOTE: 2. The THRU preamble value is also reserved for the AQC-ALE protocol.

    A.5.2.3.2.5 FROM.
  • The FROM word (100) is an optional designator which shall be used to identify the transmitting station without using an ALE frame termination, such as TIS or TWAS. It shall contain the whole address of the transmitting station, using the FROM, and if required, the DATA and REP words, exactly as described in the TO address structure in A.5.2.3.2.1. It should be used only once in each ALE frame, and it shall be used only immediately preceding a command (CMD) in the message section. Under direction of the operator or controller, it should be used to provide a "quick ID" of the transmitting station when the normal conclusion may be delayed, such as when a long message section is to be used in an ALE frame.
  • NOTE: 1. The FROM word is also reserved for future implementation of indirect and relay protocols, in which cases it may be used elsewhere in the ALE frame and with multiple addresses and other information. Stations designed in compliance with this nonrelay standard should ignore sections of calls to them that employ FROM words in any other sequence than immediately before the CMD word.

    NOTE: 2. The FROM preamble value is also reserved for the AQC-ALE protocol.

    A.5.2.3.3 Message words.

    All message words (orderwire messages) begin with a word with the CMD preamble.

    A.5.2.3.3.1 CMD.

    The CMD word (110) is a special orderwire designator which shall be used for system-wide coordination, command, control, status, information, interoperation, and other special purposes. CMD shall be used in any combination between ALE stations and operators. CMD is an optional designator which is used only within the message section of the ALE frame, and it shall have (at some time in the frame) a preceding call and a following conclusion, to ensure designation of the intended receivers and identification of the sender. The first CMD terminates the calling cycle and indicates the start of the message section of the ALE frame. The orderwire functions are directed with the CMD itself, or when combined with the REP and DATA words. See A.5.6 for message words (orderwire messages) and functions.

    A.5.2.3.4 Extension words.

    A.5.2.3.4.1 DATA.

    The DATA word (000) is a special designator which shall be used to extend the data field of any previous word type (except DATA itself) or to convey information in a message. When used with the routing designators TO, FROM, TIS, or TWAS, DATA shall perform address extension from the basic three characters to six, nine, or more (in multiples of three) when alternated with REP words. The selected limit for address extension is a total of 15 characters. When used with CMD, its function is predefined as specified in A.5.6 for message words (orderwire messages) and functions.

    A.5.2.3.4.2 REP.

    The REP word (111) is a special designator which shall be used to duplicate any previous preamble function or word meaning while changing the data field contents (bits W4 through W24). See table A-VIII. Any change of words or data field bits requires a change of preamble bits (P3 through P1) to preclude uncertainty and errors. If a word is to change, even if the data field is identical to that in the previous word, the preamble shall be changed, thereby clearly designating a word change. When used with the routing designator TO, REP performs address expansion, which enables more than one address to be specified. See A.5.2.3.2.4 for use with THRU. With DATA, REP may be used to extend and expand address, message, command, and status fields. REP shall be used to perform these functions, and it may directly follow any other word type except for itself, and except for TIS or TWAS, as there cannot be more than one transmitter for a specific call at a given time.

    NOTE 1. REP is used in Tsc of group calls directed to units with different first word addresses.

    NOTE 2. REP is not used in Tsc of calls directed to groups with same first word addresses. Also REP is not used in Tsc of calls directed to individuals and nets.

    A.5.2.4 Addressing.

    A.5.2.4.1 Introduction.

    The ALE system deploys a digital addressing structure based upon the standard 24-bit (three character) word and the Basic 38 character subset. As described below, ALE stations have the capability and flexibility to link or network with one or many prearranged or as-needed single or multiple stations. All ALE stations shall have the capacity to store and use at least 20 self addresses of up to 15 characters each in any combination of individual and net calls. There are three basic addressing methods which will be presented:

    NOTE: Certain alphanumeric address combinations may be interpreted to have special meanings for emergency or specific functions, such as "SOS," "MAYDAY," "PANPAN," "SECURITY," "ALL," "ANY," and "NULL." These should be carefully controlled or restricted.

    A.5.2.4.2 Basic 38 subset.

  • The Basic 38 subset shall include all capital alphabetics (A-Z) and all digits (0-9), plus designated utility and wildcard symbols "@" and "?," as shown in figure A-13. The Basic 38 subset shall be used for all basic addressing functions. To be a valid basic address, the word shall contain a routing preamble from A.5.2.3.2 (such as TO...), plus three alphanumeric characters (A-Z, 0-9) from the Basic 38 subset in any combination. In addition, the "@" and "?" symbols shall be used for special functions. Digital discrimination of the Basic 38 subset shall not be limited to examination of only the three MSBs (b7 through b5), as a total of 48 digital bit combinations would be possible (including ten invalid symbols which would be improperly accepted).


  • FIGURE A-13. Basic 38 subset (unshaded areas).

    A.5.2.4.3 Stuffing.

    The ALE basic address structure is based on single words which, in themselves, provide multiples of three characters. The quantity of available addresses within the system, and the flexibility of assigning addresses, are significantly increased by the use of address character stuffing. This technique allows address lengths that are not multiples of three to be compatibly contained in the standard (multiple of three characters) address fields by "stuffing" the empty trailing positions with the utility symbol "@." See table A-IX. "Stuff-1" and "Stuff-2" words shall only be used in the last word of an address, and therefore should appear only in the leading call (Tlc) of the calling cycle (Tcc).

    NOTE: As an example of proper usage, a call to the address "MIAMI" would be structured "TO MIA," "DATA MI@."

    A.5.2.4.4 Individual addresses.

    The fundamental address element in the ALE system is the single routing word, containing three characters, which forms the basic individual station address. This basic address word, used primarily for intranet and slotted operations, may be extended to multiple words and modified to provide increased address capacity and flexibility for internet and general use. An address which is assigned to a single station (within the known or used network) shall be termed an "individual" address. If it consists of one word (that is, no longer than three characters) it shall be termed a "basic" size, and if it exceeds one word, it shall be termed an "extended" size.

    TABLE A-IX. Use of "@" utility symbol.
    Pattern
    Function
    Guidance
    TO

    A B C

    "Standard" three character address structure "ABC" Any position in address and sequences
    TO

    A B @

    "Stuff-1" reduced address fields; adds characters "A, B" Only last word in address; anywhere in sequences
    TO

    A @ @

    "Stuff-2" reduced address fields; adds character "A" Only last word in address; anywhere in sequences
    TO

    @ ? @

    "Allcall" global address; all stop and listen (unless inhibited), none respond Exclusive member of calling cycle; single TO only
    TO REP

    @ A @ @ B @

    (option)

    "Selective AllCall;" global address; all with same last character "A" (or "B") stop and listen (unless inhibited), none respond Alone, or with additional different AllCall selections, for "group selective AllCall;" only in calling cycle; must use TO, REP alternately never DATA, if more than one*
    TO

    @ @ ?

    "AnyCall" global address; all stop and respond in PRN slots (unless inhibited), none respond Exclusive member of calling cycle; single TO only
    TO REP

    @ @ A @ B@

    (option)

    "Selective AnyCall;" all with same last character(s) "A" (or "B") stop and respond in PRN slots (unless inhibited), using own addresses Alone or with additional different AnyCall selections, for "group selective AnyCall;" only in calling cycle; must use TO, REP alternately (never DATA), if more than one*
    TO REP

    @ A B @ C D

    (option)

    "Double selective AnyCall;" all with same last characters "AB" (or "CD") stop and respond in PRN slots (unless inhibited), using own addresses Alone or with additional different AnyCall selections, for "group selective AnyCall;" only in calling cycle; must use TO, REP alternately (never DATA), if more than one*
    TO

    @ @ @

    "Null" address; all ignore, test and maintenance use, or extra "buffer" slot Any position in address sequence (omit from Tsc if group call) except never in conclusion (terminator), or REP, only if following TO
    NOTES:
    1. All patterns not shown here are reserved and shall be considered invalid until standardized.
    2. "@" indicates special utility character (1000000); "?" wildcard (0111111).
    3. "A," "B," "C," or "D" indicates any alphanumeric member of basic 38 subset other than "@," or "?," that is "A-Z" and "0-9."

    * THRU, REP in Tsc if group call.

    A.5.2.4.4.1 Basic size.

    The basic address word shall be composed of a routing preamble (TO, or possibly a REP which follows a TO, in Tlc of group call, or a TIS or TWAS) plus three address characters, all of which shall be alphanumeric numbers of the Basic 38 subset. The three characters in the basic individual address provide a Basic 38-address capacity of 46,656, using only the 36 alphanumerics. This three-character single word is the minimum structure. In addition, all ALE stations shall associate specific timing and control information with all own addresses, such as prearranged delays for slotted net responses. As described in A.5.5, the basic individual addresses of various station(s) may be combined to implement flexible linking and networking.

    NOTE: All ALE stations shall be assigned at least one (DO: several) single-word address for automatic use in one-word address protocols, such as slotted (multistation type) responses. This is a mandatory user requirement, not a design requirement. However, nothing in the design shall preclude using longer addresses.

    A.5.2.4.4.2 Extended size.

    Extended addresses provide address fields which are longer than one word (three characters), up to a maximum system limit of five words (15 characters). See table A-X. This 15-character capacity enables Integrated Services Digital Network (ISDN) address capability. Specifically, the ALE extended address word structure shall be composed of an initial basic address word, such as TO or TIS, as described above, plus additional words as necessary to contain the additional characters in the sequence DATA, REP, DATA, REP, for a maximum total of five words. All address characters shall be the alphanumeric members of the Basic 38 subset.

    NOTE 1: All ALE stations shall be assigned at least one (DO: several) two-word address(es) for general use, plus an additional address(es) containing the station's assigned call sign(s). This is a mandatory user requirement, not a design requirement. However, nothing in the design shall preclude using longer addresses.

    NOTE 2: The recommended standard address size for intranet, internet, and general non-ISDN use is two words. Any requirement to operate with address sizes larger than six characters must be a network management decision. As examples of proper usage, a call to "EDWARD" would be "TO EDW," "DATA ARD," and a call to "MISSISSIPPI" would be "TO MIS," "DATA SIS," "REP SIP," "DATA PI@."

    TABLE A-X. Basic (38) address structures.

    Words
    Address

    Characters


    Types
    B1 1Stuff-2
    A
    S1 2Stuff-1
    I
    C1 3Basic









    E

    X

    T

    E

    N

    D

    E

    D
















    2

    2

    2

    3

    3

    3

    4

    4

    4

    5

    5

    5

    (limit)

    4

    5

    6

    7

    8

    9

    10

    11

    12

    13

    14

    15

    (limit)

    Basic +

    Stuff-2

    Basic +

    Stuff-1

    2 Basic

    2 Basic +

    Stuff-2

    2 Basic +

    Stuff-1

    3 Basic

    3 Basic +

    Stuff-2

    3 Basic +

    Stuff-1

    4 Basic

    4 Basic +

    Stuff-2

    4 Basic +

    Stuff-1

    5 Basic

    (limit)

    NOTES:
    1. Basic : ABC
    2. Stuff-2: A@@
    3. Stuff-1: AB@

    A.5.2.4.5 Net addresses.

    The purpose of a net call is to rapidly and efficiently establish contact with multiple prearranged (net) stations (simultaneously if possible) by the use of a single net address, which is an additional address assigned to all net members in common. When a net address type function is required, a calling ALE station shall use an address structure identical to the individual station address, basic or extended as necessary. For each net address at a net member's station, there shall be a response slot identifier, plus a slot width modifier if directed by the specific standard protocol. As described in paragraphs A.5.5.3 and A.5.5.4, additional information concerning the assigned response slots (and size) must be available, and the mixing of individual, net, and group addresses and calls is restricted

    A.5.2.4.6 Group addresses.

    The purpose of a group call is to establish contact with multiple nonprearranged (group) stations (simultaneously if possible) rapidly and efficiently by the use of a compact combination of their own addresses which are assigned individually. When a group address type function is required, a calling ALE station shall use a sequence of the actual individual station addresses of the called stations, in the manner directed by the specific standard protocol. A station's address shall not appear more than once in a group calling sequence, except as specifically permitted in the group calling protocols described in A.5.5.4.

    NOTE: The group feature is not available in the AQC-ALE protocol.

    A.5.2.4.7 Allcall addresses.

    An "AllCall" is a general broadcast that does not request responses and does not designate any specific address. This mechanism is provided for emergencies ("HELP!"), broadcast data exchanges, and propagation and connectivity tracking. The global AllCall address is "@?@." The AllCall protocol is discussed in A.5.5.4.4. As a variation on the AllCall, the calling station can organize (or divide) the available but unspecified receiving stations into logical subsets, using a selective AllCall address. A selective AllCall is identical in structure, function, and protocol to the AllCall except that it specifies the last single character of the addresses of the desired subgroup of receiving stations (1/36 of all). By replacing the "?" with an alphanumeric, the selective AllCall special address pattern is "TO @A@" (or possibly "THRU @A@" and "REP @B@" if more than one subset is desired), where "A" (and "B," if applicable) in this notation represents any of the 36 alphanumerics in the Basic-38 subset. "A" and "B" may represent the same or different character from the subset, and specifically indicate which character(s) must be last in a station's address in order to stop scan and listen.

    NOTE: For ACQ-ALE, the Part2 address portion shall contain the same three characters used in the TO word of the call.

    A.5.2.4.8 AnyCalls.

    An "AnyCall" is a general broadcast that requests responses without designating any specific addressee(s). It is required for emergencies, reconstitution of systems, and creation of new networks. An ALE station may use the AnyCall to generate responses from essentially

    unspecified stations, and it thereby can identify new stations and connectivities. The global AnyCall address is "@@?." The AnyCall protocol is discussed in A.5.5.4.5. If too many responses are received to an AnyCall, or if the caller must organize the available but unspecified responders into logical subsets, a selective AnyCall protocol is used. The selective AnyCall address is identical in structure, function, and protocol to the global AnyCall, except that it specifies the last single character of the addresses of the desired subset of receiving station (1/36 of all). By replacing the "?" with an alphanumeric, the global AnyCall becomes a selective AnyCall whose special address pattern is "TO @@A." If even narrower acceptance and response criteria are required, the double selective AnyCall should be used. The double selective AnyCall is an operator selected general broadcast which is identical to the selective AnyCall described above, except that its special address (using "@AB" format) specifies the last two characters that the desired subset of receiving stations must have to initiate a response.

    NOTE: For ACQ-ALE, the Part2 address portion shall contain the same three characters used in the TO word of the call.

    A.5.2.4.9 Wildcards.

    A "wildcard" is a special character that the caller uses to address multiple-station addresses with a single-call address. The receivers shall accept the wildcard character as a substitute for any alphanumeric in their self addresses in the same position or positions. Therefore, each wildcard character shall substitute for any of 36 characters (A to Z, 0 to 9) in the Basic 38-character subset. The total lengths of the calling (wildcard) address, and the called addresses shall be the same. The special wildcard character shall be "?" (0111111). It shall substitute for any alphanumeric in the Basic 38-character subset. It shall substitute for only a single-address character position in an address, per wildcard character. See table A-XI for examples of acceptable patterns.

    TABLE A-XI. Use of "?" wildcard symbol.
    A B C BASIC "STANDARD," 1 CASE EACH
    A B ? A ? C ? B C "STANDARD" "WILD-1," 36 CASES EACH
    A ? ? ? B ? ? ? C "STANDARD" "WILD-2," 1296 CASES EACH
    ? ? ? "STANDARD" "WILD-3," 46656 CASES EACH
    A B @ "STUFF-1," 1 CASE EACH
    A ? @ ? B @ "WILD-1" "STUFF-1," 36 CASES EACH
    ? ? @ "WILD-2" "STUFF-2," 1296 CASES EACH
    A @ @ "STUFF-2," 1 CASE EACH
    ? @ @ "WILD-1" "STUFF-2," 36 CASES EACH
    @ A B "DOUBLE SELECTIVE ANYCALL," ("DSA")
    1/1296 CASES
    @ A ? "DSA" "WILD-1," 1/36 CASES
    @ ? B NOT PERMITTED. USE "SELECTIVE ANYCALL"
    @ ? ? NOT PERMITTED. USE "GLOBAL ANYCALL"
    @ @ A "SELECTIVE ANYCALL"
    @ @ ? "GLOBAL ANYCALL"
    @ A ? "SELECTIVE ALL CALL"
    @ ? @ "GLOBAL ALL CALL"
    ? @ ? "IN LINK ADDRESS"

    A.5.2.4.10 Self addresses.

    For self test, maintenance, and other purposes, stations shall be capable of using their own self addresses in calls. When a self-addressing type function is required, ALE stations shall use the following self-addressing structures and protocols. Any ALE calling structures and protocols permissible within this standard, and containing a specifically addressed calling cycle (such as "TO ABC," but not AllCall or AnyCall), shall be acceptable, except that the station may substitute (or add) any one (or several) of its own calling addresses into the calling cycle.

    A.5.2.4.11 Null address.

    For test, maintenance, buffer times, and other purposes, the station shall use a null address that is not directed to, accepted by, or responded to by any station. When an ALE station requires a null address type function, it shall use the following null address protocol. The null address special address pattern shall be "TO @@@," (or "REP @@@"), if directly after another TO. The null address shall only use the TO (or REP), and only in the calling cycle (Tcc). Null addresses may be mixed with other addresses (group call), in which case they shall appear only in the leading call (Tlc), and not in the scanning call (Tsc). Nulls shall never be used in conclusion (terminator) (TIS or TWAS). If a null address appears in a group call, no station is designated to respond in the associated slot; therefore, it remains empty (and may be used as a buffer for tune-ups, or overflow from the previous slot's responder, etc.).

    A.5.2.4.12 In-link address.

    The inlink address feature is used by a system to denote that all members in the established link are to act upon the information sent in the frame containing the inlink address. The inlink address shall be '?@?'. When a radio enters the linked condition with one or more stations, the radio shall expand the set of recognized self addresses to include the inlink address ('?@?'). When a frame is transmitted by any member of the link using the inlink address, all members are thus addressed publicly and are to use the frame information. Thus, if a linked member sent an AMD message, all members would present that message to their user. If the member sent a frame terminated with a TWAS preamble, then all members would note that the transmitting station just 'left' the link. Short messages of 'to-F?@?, to-?@?, tis-TALKINGMEMBER' would act as a keep-alive function and cause the receiving radio to extend any link termination timer.

    A.5.2.5 Frame structure.

    All ALE transmissions are based on the tones, timing, bit, and word structures described in paragraphs A.5.1 and A.5.2.3. All calls shall be composed of a "frame," which shall be constructed of contiguous redundant words in valid sequence(s) as described in figure A-14, as limited in table A-VII, and in formats as described in A.5.5. There are three basic frame sections: calling cycle, message, and conclusion. See A.5.2.5.5 for basic frame structure examples.



    FIGURE A-14. Valid word sequences.

    A.5.2.5.1 Calling cycle.

    The initial section of all frames (except sounds) is termed a calling cycle (Tcc), and it is divided into two parts: a scanning call (Tsc) and a leading call (Tlc). The scanning call shall be composed of TO words if an individual or net call (or THRU and REP words, alternating, if a group call), which contain only the first word(s) of the called station(s) or net address. The leading call shall be composed of TO (and possibly DATA and REP) words containing the whole address(es) for the called station(s), from initiation of the leading call until the start of the message section or the conclusion (thus the end of the calling cycle). See figure A-15. The use of REP and DATA is described in A.5.2.4. The set of different address first words (Tcl) may be repeated as necessary for scanning calling (Tsc), to exceed the scan period (Ts). There is no unique "flag word" or "sync word" for frame synchronization (as discussed below). Therefore, stations may acquire and begin to read an ALE signal at any point after the start. The transmitter shall have reached at least 90 percent of the selected rf power within 2.5 ms of the first tone transmission following call initiation. The end of the calling cycle may be indicated by the start of the optional quick-ID, which occupies the first words in the message section, after the leading call and before the start of the rest of the message (or conclusion, if no message) section.

    NOTE 1: The frame time may need to be delayed (equipment manufacturer dependent) to avoid loss of the leading words if the transmitter attack time is significantly long. Alternatively, the modem may transmit repeated duplicates of the scanning cycle (set of) first word(s) to be sent (not to be counted in the frame) as the transmitter rises to full power (and may even use the ALE signal momentarily instead of a tuning tone for the tuner), and then start the frame when the power is up.

    NOTE 2: The 2.5-ms permissible delay of the first ALE tone, after the transmitter has reached 90 percent of selected power, is in addition to the allowable attack time delay specified in 5.3.5.1.

    NOTE 3: Non-compliance with the 90 percent of power parameter will impact the probability of linking. Compliance testing for this can be construed to be met if the probability of linking criteria is met (see table A-I).



    FIGURE A-15. Calling cycle sequence.


    FIGURE A-15. Calling cycle sequence (continued).

    A.5.2.5.2 Message section.

    The second and optional section of all frames (except sounds) is termed a "message." Except for the quick-ID, it shall be composed of CMD (and possibly REP and DATA) words from the end of the calling cycle until the start of the conclusion (thus the end of the message). The optional quick-ID shall be composed of FROM (and possibly REP and DATA) word(s), containing the transmitter's whole address. It shall only be used once at the start of the CMD message section sequences. The quick-ID enables prompt transmitter identification and should be used if the message section length is a concern. It is never used without a following (CMD...) message(s). The message section shall always start with the first CMD (or FROM with later CMD(s)) in the call. See figure A-16. The use of REP and DATA is described in A.5.7.3. The message section is not repeated within the call (although messages or information itself, within the message section, may be).

    For AQC-ALE, the message section in AQC-ALE is available when in a link. The acknowledgement leg (third leg) of a call may be used as an inlink entry condition. See A.5.8.2.3.



    FIGURE A-16. Message sequence.


    FIGURE A-16. Message sequence (continued).

    A.5.2.5.3 Conclusion.

    The third section of all frames is termed a "conclusion." It shall be composed of either TIS or TWAS (but not both) (and possibly DATA and REP) words, from the end of the message (or calling cycle sections, if no message) until the end of the call. See figure A-17. Sounds and exception shall start immediately with TIS (or TWAS) words as described in A.5.3. REP shall not immediately follow TIS or TWAS. Both conclusions and sounds contain the whole address of the transmitting station.



    FIGURE A-17. Conclusion (terminator) sequences.


    FIGURE A-17. Conclusion (terminator) sequences (continued).

    A.5.2.5.4 Valid sequences.

    The eight ALE words types that have been described shall be used to construct frames and messages only as permitted in figures A-18, A-19, and A-20. The size and duration of ALE frames, and their parts, shall be limited as described in table A-XII.

    TABLE A-XII. Limits to frames.
    CallsLimit
    Address size (5 words) (Ta max)

    Call time maximum Tc

    (one-half of Tlc = 12 words max)

    Scan period (Ts max)

    Message section basic time (Tm max basic) (unless modified by AMD extension, or by CMD such as DTM or DBM)

    Message section, time limit of AMD (90 characters) (Tm max AMD)

    Message section time, DTM (1053

    characters) (Tm max DTM)

    Message section time, DBM (37377

    characters) (Tm max DBM)

    1960 ms

    4704 ms

    50 s

    11.76 s


    11.76 s

    2.29 min

    (entire data block)

    23.26 min

    (entire deeply interleaved block)

    A.5.2.5.5 Basic frame structure examples.

    Contained in figure A-21 are basic examples (does not include the optional message section) of frame construction. Included are single-word and multiple-word examples of either single or multiple called station address(es) for non-scan (single-channel) and scanning (multiple-channel) use in individual, net, or group calls.



    FIGURE A-18. Valid word sequence (calling cycle section).


    FIGURE A-19. Valid word sequence (message section).


    FIGURE A-20. Valid word sequence (conclusion section).


    FIGURE A-21. Basic frame structure examples.

    A.5.2.6 Synchronization.

    The ALE system is inherently asynchronous and does not require any form of system synchronization, although it is compatible with such techniques. Within a frame, the imbedded timing and structure of the system provide the necessary "hooks" for achieving and maintaining word synchronization (word sync) during linking, orderwire, and anti-interference functions, as described herein.

    A.5.2.6.1 Transmit word phase.

    The ALE transmit modulator accepts digital data from the encoder and provides modulated baseband audio to the transmitter. The signal modulation is strictly timed as described in A.5.1.3 and A.5.1.4. After the start of the first transmission by a station, the ALE transmit modulator shall maintain a constant phase relationship, within the specified timing accuracy, among all transmitted triple redundant words at all times until the final frame in the transmission is terminated. Specifically,

    T(later triple redundant word) - T(early triple redundant word) = n x Trw

    where T( ) is the event time of a given triple redundant word within any frame, Trw is the period of three words (392 ms), and n is any integer.

    NOTE: Word phase tracking will only be implemented within a transmission and not between transmissions.

    The internal word phase reference of the transmit modulator shall be independent of the receiver (which tracks incoming signals) and shall be self timed (within its required accuracy). See A.5.1.4.

    NOTE: In some applications, a single transmission may contain several frames.

    A.5.2.6.2 Receiver word sync.

    The receive demodulator accepts baseband audio from the receiver; acquires, tracks, and demodulates ALE signals; and provides the recovered digital data to the decoders. See figure
    A-11. In data block message (DBM) mode, the receive demodulator shall also be capable of reading single data bits for deep deinterleaving and decoding.

    A.5.2.6.3 Synchronization criteria.

    The decoder accepts digital data from the receive demodulator and performs deinterleaving, decoding, FEC, and data checking. During initial and continuing synchronization, all of the following criteria should be used to discriminate and read every ALE word:

    The number of unanimous votes provides an easily adjustable BER signal quality discrimination, and the threshold should be chosen by the manufacturer to optimize performance. A successful Golay decode indicates that all detected bit errors were corrected within the power of the FEC code; that is, the errors were within correctable limits and therefore, the uncorrectable error flag(s) did not occur. The correction power (mode) of the Golay code should be chosen by the manufacturer to optimize performance using any of the four modes: (3/4, 2/5, 1/6, 0/7) where n/m indicates up to "n" errors detected and corrected, or up to "m" errors detected but not correctable. Acceptable preambles, as described here and defined in A.5.2.3.1.3, refer to those preambles which are within the limits of this standard. As a DO, automatic adjustment of the unanimous vote threshold and Golay mode should be provided to optimize performance under varying conditions.

    NOTE: The application of each preamble is dependent on the recent signaling history of the stations heard, the active status of the machine, the handshake(s) expected, and the protocol being used, if any. For example, an uncommitted station, awaiting calls, would accept TO if individual or net call (and possibly THRU or REP if group call) as valid preambles for calls to it. It would reject CMD as being irrelevant (because it missed the preceding and required calling cycle Tcc). It might also reject TIS or TWAS (unless collecting sounding information). Acceptable characters means that each character is within the appropriate ASCII subset. Note that all criteria, together, must be satisfied to accept a word. For example, all three characters would have to be within the Basic 38 subset if a routing preamble such as a TO was decoded. Likewise, any bit combination would be conditionally acceptable if an initial REP was received, but in most cases, without the necessary knowledge of the previous word, it would be considered irrelevant and should be rejected.

    A.5.3 Sounding.

    A.5.3.1 Introduction.

    The sounding signal is a unilateral, one-way transmission performed at periodic intervals on unoccupied channels. To implement, a timer is added to the controller to periodically initiate sounding signals (if the channel is clear). Sounding is not an interactive, bilateral technique, such as polling. However, the identification of connectivity from a station by hearing its sounding signal does indicate a high probability (but not guarantee) of bilateral connectivity and it may be done passively at the receiver. Sounding uses the standard ALE signaling, any station can receive sounding signals. As a minimum, the signal (address) information shall be displayed to the operator and, for stations equipped with connectivity and LQA memories, the information shall be stored and used later for linking. If a station has had recent transmissions on any channels that are to be sounded on, it may not be necessary to sound on those channels again until the sounding interval, as restarted from those last transmissions, has elapsed. In addition, if a net (or group) of stations is polled, their responses shall serve as sounding signals for the other net (or group) receiving stations. All stations shall be capable of performing periodic sounding on clear prearranged channels. The sounding capability may be selectively activated by, and the period between sounds shall be adjustable by the operator or controller, according to system requirements. When available, and not otherwise committed or directed by the operator or controller, all ALE stations shall automatically and temporarily display the addresses of all stations heard, with an operator selectable alert.

    The structure of the sound is virtually identical to that of the basic call; however, the calling cycle is not needed and there is no message section. It is only necessary to send the conclusion (terminator) that identifies the transmitting station. See figure A-22. The type of word, either TIS or TWAS (but never both), indicates whether potential callers are encouraged or ignored, respectively. The minimum redundant sound time (Trs) is equal to the standard one-word address leading call time (Tlc)=784 ms. Described below are both single-channel and multiple-channel protocols, plus detailed timing and control information, for designing stations.

    A.5.3.2 Single channel.

    The fundamental capability to automatically sound on a channel shall be in accordance with the sounding protocol as shown in figure A­22. As an option, stations may employ this protocol for single-channel sounding, connectivity tracking, and the broadcast of their availability for calls and traffic. The basic protocol consists of only one part: the sound. The sound contains its own address ("TIS A"). If "A" is encouraging calls and receives one, "A" shall follow the sound with the optional handshake protocol described in A.5.3.4. If "A" plans to ignore calls, it shall use the TWAS, which advises "B" and the others not to attempt calls, and then "A" shall immediately return to normal "available." In some systems it is necessary for a multichannel station "A" to periodically sound to a single-channel network, usually to inform them that he is active and available on that channel, although scanning. Upon receipt of "A's" sound, "B" (see figure A-23) and the other stations shall display "A's" address as a received sound and, if they have an LQA and connectivity memory, they shall store the connectivity information.

    A.5.3.3 Multiple channels.

    Sounding must be compatible with the scanning timing. All stations shall be capable of performing the scanning sounding protocols described herein, even if operating on a fixed frequency. See figures A-22, A-23, and A-24. These protocols establish and positively confirm unilateral connectivity between stations on any available mutually scanned channel, and they assist in establishment of links between stations waiting for contact. Stations shall employ these protocols for multichannel sounding, connectivity tracking, and the broadcast of their availability for calls and traffic.



    FIGURE A-22. Basic sounding structure.


    FIGURE A-23. Call rejection scanning sounding protocol.

    FIGURE A-24. Call acceptance scanning sounding protocol.

    All timing considerations and computations for individual scanning calling shall apply to scanning sounding, including sounding cycle times and (optional) handshake times.

    NOTE: The scanning sound is identical to the single-channel sound except for the extension of the redundant sound time (Trs) by adding words to the scan sounding time (Tss) to form a scanning redundant sound time (Tsrs); that is Tsrs = Tss + Trs. The scan sounding time (Tss) is identical in purpose to the scan calling time (Tsc) for an equivalent scanning situation, but it only uses the whole address of the transmitter.

    The channel-scanning sequences and selection criteria for individual scanning calling shall also apply to scanning sounding. The channels to be sounded are termed a "sound set," and usually are identical to the "scan set" used for scanning. See figure A-23. In this illustration, station "A" is sounding and station "B" is scanning normally. If a station "A" plans to ignore calls (from "B"), which may follow "A's" sound, the following call rejection scanning sounding protocol shall be used. In a manner identical to the previously described individual scanning call, "A" lands on the first channel in the scan set (1), waits (Twt) to see if the channel is clear (3), tunes (Tt) its coupler, comes to full power, and initiates the frame of the scanning redundant sound times (Tsrs). This scanning sound is computed to exceed "B's" (and any others) scan period (Ts) by at least a redundant sound time (Trs), which will ensure an available detection period exceeding Tdrw = 784 ms. In this five-channel example, with "B" scanning at 5 chps, "A" sounds for at least 12 Trw (4704 ms). "A" also uses "TWAS A," redundantly to indicate that calls are not invited. Upon completion of the scanning sounding frame transmission, "A" immediately leaves the channel and goes to the next channel in the sound set. This procedure repeats until all channels have been sounded, or skipped if occupied. When the calling ALE station has exhausted all the prearranged sound set channels, it shall automatically return to the normal "available" receive scan mode. As shown in figure A-23, the timing of both "A" and "B" have been prearranged to ensure that "B" has at least one opportunity, on each channel, to arrive and "capture" "A's" sound. Specifically, "B" arrives, detects sounds, waits for good words, reads at least three (redundant) "TWAS A" (in 3 to 4 Tw), stores the connectivity information (if capable), and departs immediately to resume scan.

    There are several specific protocol differences when station "A" plans to welcome calls after the sound. See figure A-24. In this illustration, "A" is sounding and "B" is scanning normally. If station "A" plans to welcome calls (from "B"), which may follow his sound, the following call acceptance scanning sounding protocol shall be used. In this protocol, "A" sounds for the same time period as before. However, since "A" is receptive to calls, he shall use his normal scanning dwell time (Td) or his preset wait before transmit time (Twt), whichever is longer, to listen for both channel activity and calls before sounding. If the channel is clear, "A" shall initiate the scanning sound identically to before, but with "TIS A." At the end of the sounding frame, "A" shall wait for calls identically to the wait for reply and tune time (Twrt) in the individual scanning calling protocol, in this case shown to be 6 Tw (for fast-tuning stations). During this wait, "A" shall (as always) be listening for calls that may coincidentally arrive even though unassociated with "A's" sound, plus any other sound heard, which "A" shall store as connectivity information if polling-capable. If no calls are received, "A" shall leave the channel.

    A.5.3.4 Optional handshake.

    In the previous descriptions, one alternative action is the implementation of an optional handshake with a station immediately after its sound. This protocol is identical in all regards to the single channel individual call protocol, except that it is manually or automatically (operator or controller) triggered by acquisition of connectivity from the station that is to be called. See figure A-25. In this illustration, "A" is scanning sounding and is receptive to calls, and "B" is receive scanning (or waiting in ambush on a channel) and requires contact with "A" if heard. "A" uses the standard call acceptance scanning sound, including the "TIS A" and the pause for calls. In this case "B" calls "A." When ALE stations are scanning sounding and receptive to calls, or required contact with such a station, the optional handshake protocol should be used. The calling station should immediately initiate the call upon the determination that the station to be called has terminated its transmission. A wait time before transmit time is not required. Therefore, if "B" hears "A's" sound and is seeking "A," "B" calls immediately using the simple single-channel call. Also, if "B's" operator or controller identifies "A's" address it can attempt the optional handshake.



    FIGURE A-25. Scanning sounding with optional handshake protocol.

    A.5.4 Channel selection.

    Channel selection is based on the information stored within the LQA memory (such as BER, SINAD, and MP) and this information is used to speed connectivity and to optimize the choice of quality channels. When initiating scanning (multichannel) calling attempts, the sequence of channels to be tried shall be derived from information in the LQA memory with the channel(s) with the "best score(s)" being tried first (unless otherwise directed by the operator or controller) until all the LQA scored channels are tried. However, if LQA or other such information is unavailable (or it has been exhausted and other valid channels remain available and untried) the station shall continue calling on those channels until successful or until all the remaining (untried valid) channels have been tried.

    A.5.4.1 LQA.

    LQA data shall be used to score the channels and to support selection of a "best" (or an acceptable) channel for calling and communication. LQA shall also be used for continual monitoring of the link(s) quality during communications that use ALE signaling. The stored values shall be available to be transmitted upon request, or as the network manager shall direct. Unless specifically and otherwise directed by the operator or controller, all ALE stations shall automatically insert the CMD LQA word (t) in the message section of their signals and handshakes when requested by the handshaking station(s), when prearranged in a network, or when specified by the protocol. See A.5.4.2. If an ALE station requires, and is capable of using LQA information (polling-capable), it may request the data from another station by setting the control bit KA1 to "1" in the CMD LQA word. If an ALE station, which is sending CMD LQA in response to a request is incapable of using such information itself (not polling-capable), it shall set the control bit KA1 to "0." It will be a network management decision to determine if the LQA is to be active or passive. For human factor considerations, LQA scores that may be presented to the operator should have higher (number) scores for better channels.

    A.5.4.1.1 BER.

    Analysis of the BER on rf channels, with respect to poor channels and the 8-ary modulation, plus the design and use of both redundancy and Golay FEC, shows that a coarse estimate of BER may be obtained by counting the number of non-unanimous (2/3) votes (out of 48) in the majority vote decoder. The range of this measure is 0 through 48. Correspondence to actual BER values is shown in table A-XIII.

    After an ALE receiver achieves word synchronization (see A.5.2.6.2), all received words in a frame shall be measured, and a linear average BER/LQA shall be computed as follows:

    At the end of the transmission, the total shall be divided by the number of words received, and the total shall be stored in the Link Quality Memory as the most current BER code for the station sending the measured transmission and the channel that carried it.

    A.5.4.1.2 SINAD.

    The signal to noise and distortion measurement shall be a SINAD measurement ((S+N+D)/(N+D)) averaged over the duration of each received ALE signal. The SINAD values shall be measured on all ALE signals.

    A.5.4.1.3 MP (optional).

    Measurement of MP using received ALE signals is optional.

    A.5.4.1.4 Operator display (optional).

    Display of SINAD values shall be in dB.

    A.5.4.2 Current channel quality report (LQA CMD).

    This mandatory function is designed to support the exchange of current LQA information among ALE stations. The CMD LQA word shall be constructed as shown in table A-XIV The preamble shall be CMD (110) in bits P3 through P1 (W1 through W3). The first character shall be "a" (1100001) in bits C1-7 through C1-1 (W4 through W10), which shall identify the LQA function "analysis." It carries three types of analysis information (BER, SINAD, and MP) which are separately generated by the ALE analysis capability. Note that when the control bit KA1 (W11) is set to "1," the receiving station shall respond with an LQA report in the handshake. If KA1 is set to "0," the report is not required.

    A.5.4.2.1 BER field in LQA CMD.

    Measurement and reporting of BER is mandatory. The BER field in the LQA CMD shall contain five bits of information, BE5 through BE1 (W20 through W24). Refer to table A-XIII for the assigned values.

    A.5.4.2.2 SINAD.

    SINAD shall be reported in the CMD LQA word as follows. The SINAD is represented as five bits of information SN5 through SN1 (W15 through W19). The range is 0 to 30 dB in 1-dB steps. 00000 is 0 dB or less, and 11111 is no measurement.

    A.5.4.2.3 MP.

    If implemented, MP measurements shall be reported in CMD LQA words in the three bits, MP3 through MP1 (W12 through W14). The measured value in ms shall be reported rounded to the nearest integer, except that values greater than 6 ms shall be reported as 6 (110). When MP is not measured, the reported MP value shall be 7 (111).

    TABLE A-XIII. Basic BER values.

    Average 2/3

    Votes Counted

    LQA Transmission Bits

    MSB LSB


    Approximate

    BER

    BE5 BE4BE3 BE2BE1
    00 00 00 0.0
    10 00 01 0.006993
    20 00 10 0.01409
    30 00 11 0.02129
    40 01 00 0.02860
    50 01 01 0.03602
    60 01 10 0.04356
    70 01 11 0.05124
    80 10 00 0.05904
    90 10 01 0.06699
    100 10 10 0.07508
    110 10 11 0.08333
    120 11 00 0.09175
    130 11 01 0.1003
    140 11 10 0.1091
    150 11 11 0.1181
    161 00 00 0.1273
    171 00 01 0.1368
    181 00 10 0.1464
    191 00 11 0.1564
    201 01 00 0.1667
    211 01 01 0.1773
    221 01 10 0.1882
    231 01 11 0.1995
    241 10 00 0.2113
    251 10 01 0.2236
    261 10 10 0.2365
    271 10 11 0.2500
    281 11 00 0.2643
    291 11 01 0.2795
    30 (or more)1 11 10 0.3 (or more)
    - -1 11 11 no value available

    TABLE A-XIV. Link quality analysis structure.
    LQA Bits Word Bits
    CMD

    Preamble

    MSB
    P3=1

    P2=1

    P1=0

    MSBW1

    W2

    W3

    First

    Character

    "a"

    MSB




    LSB

    C1-7=1

    C1-6=1

    C1-5=0

    C1-4=0

    C1-3=0

    C1-2=0

    C1-1=1

    W4

    W5

    W6

    W7

    W8

    W9

    W10

    Control KA1 W11
    MP

    Bits

    MSB

    LSB

    MP3

    MP2

    MP1

    W12

    W13

    W14

    SINAD

    Bits

    MSB


    LSB

    SN5

    SN4

    SN3

    SN2

    SN1

    W15

    W16

    W17

    W18

    W19

    BER

    Bits

    MSB


    LSB

    BE5

    BE4

    BE3

    BE2

    BE1





    LSB
    W20

    W21

    W22

    W23

    W24


    NOTES:
    1. Command LQA first character is "a" (1100001) for "analysis."
    2. Control bit KA1 (W11) requests an LQA within the handshake from the called station, if set to "1," and suppresses LQA if set to "0."

    A.5.4.3 Historical LQA report.

    See MIL-STD-187-721.

    A.5.4.4 Local noise report CMD (optional).

    The Local Noise Report CMD provides a broadcast alternative to sounding that permits receiving stations to approximately predict the bilateral link quality for the channel carrying the report. An example application of this optional technique is networks in which most stations are silent but need to have a high probability of linking on the first attempt with a base station. A station receiving a Local Noise Report can compare the noise level at the transmitter to its own local noise level, and thereby estimate the bilateral link quality from its own LQA measurement of the received noise report transmission. The CMD reports the mean and maximum noise power measured on the channel in the past 60 minutes.

    The Local Noise Report CMD shall be formatted as shown in figure A-26. Units for the Max and Mean fields are dB relative to 0.1 µV 3 KHz noise. If the local noise measurement to be reported is 0 dB or less, a 0 is sent. For measured noise ratios of 0 dB to +126 dB, the ratio in dB is rounded to an integer and sent. For noise ratios greater than +126 dB, 126 is sent. The code 127 (all 1s) is sent when no report is available for a field. By comparing the noise levels reported by a distant station on several channels, the station receiving the noise reports can select a channel for linking attempts based upon knowledge of both the propagation characteristics and the interference situation at that destination.
    3
    7
    7
    7
    CMD
    Noise Report (ASCII 'n') MaxMean
    110
    1101110

    FIGURE A-26. Local noise report (optional).

    A.5.4.5 Single-station channel selection.

    All stations shall be capable of selecting the (recent) best channel for calling or listening for a single station based on the values in the LQA memory.

    A.5.4.5.1 Single-station channel selection for link establishment.

    When selecting a channel for a two-way link, link quality measurements for both directions on each frequency must be considered. Figure A-27 represents a simple LQA memory example. For each address/channel cell, the measured LQA (upper section) and reported LQA values (lower section) are stored. Bilateral (handshake) scores in this example are the sum of the two LQA values.

    NOTE 1: For operator viewing, LQA values for better channels should be displayed as higher numbers, and values for poorer channels should be displayed as lower numbers.

    NOTE 2: In the example shown in figure A-27, if a handshake is required with station "B," channel C3 would be the best because the "round trip" (bilateral) score would be 5 (1+4), thus the lowest, channel C4 is next best with a score of 6 (3+3), the C5 with 7, C2 with 12, and C6 with 18. Linking attempts should be made in that order (C3, C4, C5, C2, and C6).

    C1 is left until last because of the "x", which indicates that a recent attempted handshake on that channel failed to link. Similarly, an attempt to call "A" would yield the sequence C3(3), C5(12), C2(12), C1(24), C6(26), and C4(x). In this case, C5 was equal to C2 (both are 12), but C5 was chosen first because the paths were more balanced (LQA values were more equal).



    FIGURE A-27. LQA memory example.

    A.5.4.5.2 Single-station channel selection for one-way broadcast.

    If only a one-way transmission to a station is required instead of a handshake, the scores reported by the destination station (TO section in figure A-27) should be given greater weight than the scores measured on transmissions from that station.

    NOTE: In the example, to reach "B," the sequence would be C4(3), C3(4), C5(5), C2(7), C6(12), and C1(x) as a last resort.

    A.5.4.5.3 Single-station channel selection for listening.

    When selecting a channel to listen for another station, the scores measured on transmissions from that station (FROM section in figure A-27) should be given greater weight than the scores reported by the destination station.

    NOTE: In the example, to listen for "A," channel C4(0) would be best, and if only three channels were to be scanned, they should be C4, C3, and C2.

    A.5.4.6 Multiple-station channel selection.

    A station shall also be capable of selecting the (recent) best channel to call or listen for multiple stations, based on the values in the LQA memory.

    NOTE: In the example shown in figure A-27, if a multiple-station handshake is required with stations "B" and "C," C5 is the best choice as the total score is 12 (2+5+3+2), followed by C4 (20) and C3 (35). Next would be C2 (34+) and C6 (36+), this ranking being due to their unknown handshake capability (which had not been tried). C1(x) is the last to be tried because recent handshake attempts had failed for both "B" and "C." To call the three stations "A," "B," and "C," the sequence would be C5 (24), C3 (38), C2 (46+), C6 (62+), C4 (one x) (recently failed attempt), and finally C1 (two x).

    If an additional selection factor is used, it will change the channel selection sequence.

    NOTE: In the example, to call "D" and "E," the sequence would be C2, C3, C4, C5, C1, and C6. If a maximum limit of LQA < 14 is imposed on any path (to achieve a minimum circuit quality), only C2 and C3 would be initially selected for the linking attempt. Further, if the LQA limit was "lowered" to 10, C3 would be selected before C2 for the linking attempt.

    If a broadcast to multiple stations is required, the TO section ("to" the station) scores are given priority.

    NOTE: In the example, to broadcast to "B" and "C," the sequence would be C5(7), C4(9), C3(21), C2(7+), C6(12+), and C1(two x).

    To select channels for listening for multiple stations, the FROM section ("from" the station) scores are given priority.

    NOTE: In the example, to listen for "A" and "B," channel C2 (2) would be best, and if only four channels could be scanned, they should be C2, C3, C4, and C5.

    A.5.4.7 Listen before transmit.

    Before initiating a call or a sound on a channel, an ALE controller shall listen for a programmable time (Twt) for other traffic, and shall not transmit on that channel if traffic is detected. Normally, a sound aborted due to detected traffic will be rescheduled, while for a call another channel shall be selected.

    A.5.4.7.1 Listen-before-transmit duration.

    The duration of the listen-before-transmit pause shall be programmable by the network manager. When the selected channel is known to be used only for ALE transmissions, the listen-before-transmit delay need be no longer than 2 Trw. For other channels, at least 2 seconds shall be used. When an ALE controller was already listening on the channel selected for a transmission, the time spent listening on the channel may be included in the listen-before-transmit time.

    A.5.4.7.2 Modulations to be detected.

    The listen-before-transmit function shall detect traffic on a channel in accordance with A.4.2.2. This may be accomplished using any combination of internal signal detection and external devices that provide a channel busy signal to the ALE controller.

    A.5.4.7.3 Listen before transmit override.

    The operator shall be able to override both the listen-before-transmit pause and the transmit lockout (for emergency use).

    A.5.5 Link establishment protocols.

    An ALE controller shall control an attached HF SSB radio to support both manual and automatic link operation as described in the following paragraphs.

    A.5.5.1 Manual operation.

    The ALE controller shall support emergency control by the operator. Each ALE controller shall provide a manual control capability to permit an operator to directly operate the basic SSB radio in emergency situations. At all other times, the radio shall be under automated control, and the operator should operate the radio through its associated controller. The ALE controller's receiving and passive collection capability to be "always listening," such as monitoring for sounding signals or alerting the operator, shall not be impaired.

    NOTE: This does not abrogate the manual push-to-talk operation required by 4.2.2.

    A.5.5.2 ALE.

    The fundamental protocol exchange for link establishment shall be the three-way handshake (see Appendix I for overview of Selective Calling). A three-way handshake is sufficient to establish a link between a calling station and a responding station. With the addition of slotted responses (described in A.5.5.4.2), the same call/response/acknowledgment sequence can also link a single calling station to multiple responding stations.

    A.5.5.2.1 Timing.

    The ALE system depends on a selection of timing functions for optimizing the efficiency and effectiveness of ALE. The primary timing functions and values as listed in table A-XV. Annex A defines the timing symbols and Annex B explains the timing analysis and computation.

    A.5.5.2.2 ALE states.

    An ALE controller may be referred to as being in one of three conceptual "states." See figure
    A-28.

    FIGURE A-28. Link establishment states.

    A.5.5.2.3 ALE channel selection.

    A scanning calling station shall send ALE calls on its scanned channels in the order dictated by its channel selection algorithm. It shall link on the first channel it tries that supports a handshake with the called station(s).

    A.5.5.2.3.1 Rejected channel.

    If a channel is rejected after linking by the operator or controller as unsuitable, the ALE controller shall terminate the link in accordance with A.5.5.3.5 and shall update LQA data using measurements obtained during linking.

    A.5.5.2.3.2 Busy channel.

    During the scanning-calling cycle, a caller may encounter occupied channels and shall skip them to avoid interference to traffic and activity. After all available channels have been tried, if no contact has been successful, the caller should revisit the previously occupied channels and, if they are free, attempt to call.

    A.5.5.2.3.3 Exhausted channel list.

    If a calling station has exhausted all of its prearranged scan set channels and failed to establish a link, it shall immediately return to normal receive scanning (the available state). It shall also alert the operator (and networking controller if present) that the calling attempt was unsuccessful.

    A.5.5.2.4 End of frame detection.

    ALE controllers shall identify the end of a received ALE signal by the following methods. The controller shall search for a valid conclusion (TIS or TWAS, possibly followed by DATA and REP for a maximum of five words, or Tx max). The conclusion must maintain constant redundant word phase within itself (if a sound) and with associated previous words. The controller shall examine each successive redundant word phase (Trw) following the TIS (or TWAS) for the first (of up to four) non-readable or invalid word(s). Failure to detect a proper word (or detection of an improper word) or detection of the last REP, plus the last word wait delay time, (Tlww or Trw), shall indicate the end of the received transmission. The maximal acceptable terminator sequence is TIS (or TWAS), DATA, REP, DATA, REP.

    TABLE A-XV. Timing.
    NOTE: Refer to annex A and annex B for details.
    Basic system timing
    • Tone rate = 125 symbols per second (sps)
    • Tone period = Ttone = 8 ms
    • On-air rate = 375 b/s
    • On-air word: Tw = 130.66... ms
    • On-air redundant word: Trw = 3 Tw = 392 ms
    • On-air leading redundant words: Tlrw = 2 Trw = 784 ms
    • On-air individual (net) address time: Ta = m x Trw for m = 1 to 5 max words.

    Ta = 392 ms to 1960 ms

    • Propagation: Tp = 0 to 70 ms
    System timing limits
    • Address size limit 5 words: Ta max = 1960 ms
    • Address first word limit: Tal = 392 ms
    • Call time maximum: Tc = 4704 ms (one-half of Tlc = 12 words max)
    • Group addresses first word limit: Tcl = 1960 ms
    • Maximum scan period: Ts max = 50 s
    • Message section basic time (unless modified by AMD extension, or by CMD (such as DTM or DBM)): Tm max basic = 11.76s
    • Message section time limit, AMD (90 characters): Tm max AMD = 11.76s
    • Message section time limit, DTM (1053 characters): Tm max DTM = 2.29 min (entire data block)
    • Message section time limit, DBM, (37377 characters): Tm max DBM = 23.26 min (entire deeply interleaved block with CMD)
    • Termination time limit: Tx max = 1960 ms
    If an ALE (orderwire) protocol such as AMD, DTM, or DBM is used to extend the basic message section, it shall start no later than the start of the 30th word (11.368 s). Such extension of the message section shall be determined by the length of the extended ALE protocol, and the message section shall terminate at the end of the orderwire without additional extension. The conclusion shall start at the end of the message section.
    Individual calling
    • Minimum dwell time: Td (5) min = 200 ms, basic receive scanning (5 channels per second)
    • Minimum dwell time: Td (2) min = 500 ms minimum receive scanning (2 channels per second (chps))
    • Probable maximum dwell per channel, for channel, for Ts computations, let Td = Tdrw =784 ms
    • Number of channels: C
    • Scan period: Ts = C x Td
    • Call time: Tc = Ta (one or more whole addresses as required S Ta) in Tlc
    • Call time (Group Call): Tcl = Tal (one or more different first words, S Tal) in Tsc
    • Leading call time: Tlc = 2 Tc
    • Redundant call time: Trc = Tlc + Tx
    • Scanning call time: Tsc = n x Tcl ³ Ts
    • Calling cycle time: Tcc = Tsc + Tlc ³ Ts + Tlc
    • Scanning redundant call time: Tsrc = Tsc + Trc
    • Last word wait delay: Tlww = Trw = 392 ms
    • Wait for response time delay: Twr = Ttd + Tp + Tlww + Tta + Trwp (if not first transmission...) + Tld + Tp + Trd
    • Late detect delay: Tld = Tw = 130.66...ms

    TABLE A-XV. Timing (continued).
    • Redundant word phase delay: Trwp = 0 to Trw (0 to 392 ms)
    • Turnaround time: Tta = Trd + Tdek + Tenk + Ttc + Ttk + Ttd
    • Wait for calling cycle end time: Twce = 2 x own Ts (default)
    • Tune time: Tt (as required by slowest tuner)
    • Wait for reply and tune time: Twrt = Twr + Tt
    • Detect signaling period: Tds £ (Td(5) = 200 ms)
    • Detect redundant word period: Tdrw = Trw + spare Trw = 784 ms
    • Detect rotating redundant word period: Tdrrw = 2 Trw + spare

    Trw = 1176 ms

    Sounding
    • Redundant sound time (similar to Tlc): Trs = 2 Ta (caller)
    • Scanning sound time (similar to Tsc): Tss = n x Ta (caller) ³ T
    • Scanning redundant sound time (similar to Tcc): Tsrs = Tss + Trs ³ Ts + Trs
    Star calling
    • Minimum standard slot widths: Tsw min = 14, 17 Tw for 1st handshake slots, or 17, 20 for subsequent handshake slots, or other Tw as set by CMD.
    • Slot widths: Tsw = 14, 17, 9, or other Tw
    • Slot number: SN
    • Slot wait time: Tswt = Tsw x SN (uniform case)
    • Slot wait time (delay to start reply): Tswt for each slot is the sum of all the previous slot times and so must be different for each slot and is cumulative. Tswt(SN) = Tsw x SN for uniform slots or generally Tswt(SN) = SN x [5 Tw + 2 Ta (caller) + (optional LQA)Trw + (optional message)Tm] + Ta (caller) + [(sum of all previous called addressed)

    m=SN-1

    S Ta(m) (called)]

    m=1

    • Number of slots: NS
    • Wait for net reply (at calling station): Twrn = (Tsw x NS) for uniform slots, or generally Twrn = Tswt(NS)
    • Wait for net acknowledgment (at called stations): Twan = Twrn + Tdrw
    • Turnaround and tune limits: Tta + Tt £ 360, 2100, or 1500 ms, depending on whether slot 0, 1, or others
    • Maximum star group wait for acknowledgment: Twan max = 107 Tw + 27 Ta (caller) + 13 Trw (optional LQA) + 13 Tm (optional message)
    • For late arrival stations, if caller uses one word addresses and no message calling: Twan max = 188 Tw, or 227 Tw if LQA
    Programmable timing parameters: typical values
    • Wait (listen first): Twt = 2 seconds, general uses; = 784 ms, ALE/data only channels
    • Tune time: Tt = 8 Tw = 1045.33...ms (default), "blind" first call; = 20 seconds, next try
    • Automatic sounding: Tps = 30 minutes
    • Wait for activity: Twa = 30 seconds

    A.5.5.3 One-to-one calling.

    The protocol for establishing a link between two individual stations shall consist of three ALE frames: a call, a response, and an acknowledgment. The sequence of events, and the timeouts involved, are discussed in the following paragraphs using a calling station SAM and a called station JOE.

    A.5.5.3.1 Sending an individual call.

    After selecting a channel for calling, the calling station (SAM) shall begin the protocol by first listening on the channel to avoid "disturbing active channels," and then tuning. If the called station (JOE) is known to be listening on the chosen channel (not scanning), the calling station shall transmit a single-channel call that contains only a leading call and a conclusion (see upper frame in figure A-29). Otherwise, it shall send a longer calling cycle that precedes the leading call with a scanning call of sufficient length to capture the called station's receiver as it scans (lower frame in figure A-29). The duration of this scanning call shall be 2 Trw for each channel that the called station is scanning. The scanning call section shall contain only the first word of the called station address, using a TO preamble, and repeated as necessary until the end of the scanning call section.

    FIGURE A-29. Individual calls.

    The entire called station address shall be used in the leading call section, and shall be sent twice (see figure A-29) using a TO preamble each time the first word is sent and DATA and REP as required for additional words.

    Any message section CMDs shall be sent immediately following the leading call, followed by a conclusion containing the complete calling station address ("TIS SAM"). The calling station shall then wait a preset reply time to start to receive the called station's response. In the single-channel case, the wait for reply time shall be Twr, which includes anticipated round trip propagation delay and the called station's turnaround time. In the multi-channel case, the calling station shall wait through a wait for reply and tune time (Twrt), which also includes time for the called station to tune up on the chosen channel.

    If the expected reply from the called station does not start to arrive within the preset wait for reply time (Twr) or wait for reply and tune time (Twrt), the linking attempt on this channel has failed. At this point, if other channels in the scan set have not been tried, the linking attempt will normally start over on a new channel. Otherwise, the ALE controller shall return to the available state, and the calling station's operator or networking controller shall be notified of the failed linking attempt.

    A.5.5.3.2 Receiving an individual call.

    When the called station (JOE) arrives on channel, sometime during its scan period Ts, and therefore during the calling station SAM's longer scan calling time Tsc, the called station shall attempt to detect ALE signaling within its dwell time. If ALE signaling is detected, and the controller achieves word sync, it shall examine the received word to determine the appropriate action.

    If JOE reads "TO JOE" (or an acceptable equivalent according to protocols), the ALE controller shall stop scan, enter the linking state, and continue to read ALE words while waiting a preset, limited time Twce for the calling cycle to end and the message or conclusion to begin.

    While reading a call in the linking state, the called station shall evaluate each new received word. The controller shall immediately abort the handshake and return to its previous state upon the occurrence of any of the following:

    If a quick-ID or a message section starts within Twce, the called station, (JOE) shall attempt to read one or more complete messages within a new preset, limited time Tmmax

    If a frame conclusion starts "TIS SAM," the called station shall wait and attempt to read the calling station's address (SAM) within a new preset, limited time Txmax.

    If an acceptable conclusion sequence with TIS is read, the called station shall start a "last word wait" timeout Tlww = Trw while searching for additional address words (if any) and the end of the frame (absence of a detected word), which shall trigger its response. The called station will also expect the calling station to continue the handshake (with an acknowledgment) within the called station's reply window, Twr, after its response. If TWAS is read instead, the called station shall not respond but shall return to its previous state immediately after reading the entire calling station address.

    If all of the above criteria for responding are satisfied, the called station shall initiate an ALE response immediately after detecting the end of the call, unless otherwise directed by the operator or controller.

    A.5.5.3.3 Response.

    Upon receipt of a call that is addressed to one of its own self addresses (JOE), and which contains a valid calling station address in a TIS conclusion (SAM), the called station shall listen for other traffic on the channel. If the channel is not in use, the station shall tune up, send a response (figure A-30), and start its own reply timer Twr. (The longer Twrt timeout is not necessary unless the calling station will send its acknowledgment on a different channel than the one carrying the call, requiring re-tuning.) If the channel is in use, the ALE controller shall ignore the call and return to its previous state unless otherwise programmed.

    FIGURE A-30. Response frame.

    If the calling station (SAM) successfully reads the beginning of an appropriate response ("TO SAM") starting within its timeout (either Twr or Twrt), it shall process the rest of the frame in accordance with the checks and timeouts described above for the call until it either aborts the handshake or receives the appropriate conclusion, which in this example is "TIS JOE."

    Specifically, the calling station shall immediately abort the handshake upon the occurrence of any of the following:

    After aborting a handshake for any of the above reasons, the calling station will normally restart the calling protocol, usually on another channel.

    If the calling station receives the proper conclusion from the called station ("TIS JOE") starting within Tlc (plus Tm max, if message included), it shall set a last word wait timeout as above and prepare to send an acknowledgment. If, instead, "TWAS JOE" is received, the called station has rejected the linking attempt, the calling station ALE controller shall abort the linking attempt and inform the operator of the rejected attempt.

    A.5.5.3.4 Acknowledgment.

    If all of the above criteria for an acceptable response are satisfied, and if not otherwise directed by the operator or networking controller, the calling station ALE controller shall alert its operator that a correct response has been received, send an ALE acknowledgment (see figure A-31), enter the linked state with the called station (JOE), and unmute the speaker.

    FIGURE A-31. Acknowledgment frame.

    A "wait for activity" timer Twa shall be started (with a typical timeout of 30 seconds) that shall cause the link to be dropped if the link remains unused for extended periods (see A.5.5.3.5).

    If the called station (JOE) successfully reads the beginning of an appropriate acknowledgment ("TO JOE") starting within its Twr timeout, it shall process the rest of the frame in accordance with the checks and timeouts described above for the response until it either aborts the handshake or receives the appropriate conclusion, which in this example is "TIS SAM" or "TWAS SAM."

    Specifically, the calling station shall immediately abort the handshake upon the occurrence of any of the following:

    If the handshake is aborted for any of the above reasons, the handshake has failed, and the called station ALE controller shall return to its pre-linking state. The called station shall notify the operator or controller of the failed linking attempt.

    Otherwise, the called station shall enter the linked state with the calling station ("SAM"), alert the operator (and network controller if present), unmute the speaker, and set a wait-for-activity timeout Twa.

    NOTE 1: Although SAM's acknowledgment to JOE appears identical to a single-channel individual call from SAM to JOE, it does not cause JOE to provide another response to the acknowledgment (resulting in an endless "ping-pong" handshake) because SAM's acknowledgment arrives within a narrow time window (Twr) after JOE's response, and an acknowledge (ACK) from SAM is expected within this window. If SAM's acknowledgment arrives late (after Twr), however, then JOE must treat it as a new individual call (and shall therefore send a new response, if SAM concludes the frame with TIS).

    NOTE 2: A typical one-to-one scanning call three-way handshake takes between 9 and 14 seconds.

    A.5.5.3.5 Link termination.

    Termination of a link after a successful linking handshake shall be accomplished by sending a frame concluded with TWAS to any linked station(s) which is (are) to be terminated. For example, "TO JOE, TO JOE, TWAS SAM" (when sent by SAM) shall terminate the link between stations SAM and JOE. JOE shall immediately mute and return to the available state, unless it still retains a link with any other stations on the channel. Likewise, SAM shall also immediately mute and return to the available state, unless it retains a link with any other stations on the channel.

    A.5.5.3.5.1 Manual termination.

    A means shall be provided for operators to manually reset a station, which shall mute the speaker(s), return the ALE controller to the available state, and send a link terminating (TWAS) transmission, as specified above, to all linked stations, unless this latter feature is overridden by the operator. (DO: provide a manual disconnect feature that drops individual links while leaving others in place.)

    A.5.5.3.5.2 Automatic termination.

    If no voice, data, or control traffic is sent or received by a station within a preset time limit for activity (Twa), the ALE controller shall automatically mute the speaker, terminate the linked state with any linked stations, and return to the available state. The wait for the activity timer is mandatory, but shall also be capable of being disabled by the operator or network manager. This timed reset is not required to cause a termination (TWAS) transmission, as specified above. However, it is recommended that a termination be sent to reset the other linked stations(s) to immediately return them to the available state.

    Termination during a handshake or protocol by the use of TWAS (or a timer) should cause the receiving (or timed-out) station to end the handshake or protocol, terminate the link with that station, re-mute, and immediately return to the available state unless it still retains a link with another station.

    A.5.5.3.6 Collision detection.

    While receiving an ALE signal, it is possible for the continuity of the received signal to be lost (due to such factors as interference or fading) as indicated by failure to detect a good ALE word at a Trw boundary. When one or both Golay words of a received ALE word contain uncorrectable errors, the ALE controller shall attempt to regain word sync, with a bias in favor of words that arrive with the same word phase as the interrupted frame.

    If word sync is reacquired but at a new word phase, this indicates that a collision has occurred. The interrupted frame shall be discarded, and the interrupting signal processed as a new ALE frame.

    NOTE: Stations should be able to read interfering ALE signals, as they may contain useful (or critical) information, for which the station is "always listening."

    A.5.5.4 One-to-many calling.

    One station may simultaneously establish a multi-way link with multiple other stations using the protocols described in the following subparagraphs.

    A.5.5.4.1 Slotted responses.

    The simple three-way handshake used for individual links cannot be used for one-to-many calling because the responses from the called stations would collide with each other. Instead, a time-division multiple access (TDMA) scheme is used. Each responding station shall send its response in an assigned or computed time slot as described later for the particular one-to-many protocol.

    At the end of a one-to-many call frame, the following events shall take place:

    As each station's slot wait timer expires, it shall send its response and continue to await the expiration of its WRTT. Should that timer expire before the start of an acknowledgment from the calling station, the called station shall abort the linking attempt, and return to its pre-linking state.

    A.5.5.4.1.1 Slotted response frames.

    Slotted response frames shall be formatted identically to responses in the one-to-one calling protocol (see figure A-32), including a leading call, an optional message section, and a frame conclusion. A responding station shall conclude its response with TIS to accept the call, or TWAS to reject it. When the calling and responding addresses are one-word (as shown), slots are each 14 Tw, or about 1.8 seconds.



    FIGURE A-32. Slotted responses.
    A.5.5.4.1.2 Slot widths.

    Unless otherwise specified, all slots shall be 14 Tw in duration, which allows response frames with single-word addresses to propagate to and from the other side of the globe and use commonly available HF transceivers and tuners. When any slot is extended, all following slots shall be delayed commensurately.

    A.5.5.4.1.3 Slot wait time formula.

    The general formula for determining the correct timing for slotted responses in nonminimum or nonuniform cases is as follows for a selected slot number denoted SN:

    Tswt(SN) = SN x [5 Tw + 2 Ta (caller) + (optional message) Tm] + Ta (caller) +

    m = SN-1

    S Ta (m) (called)

    m=1

    Where Ta (caller) is the address length (an integer multiple of Trw) of the calling station,

    (optional message)Tm is an optional message section (same size for all slots), present if and only if requested in the call. Ta(m) (called) is the address length of the station that will respond in slot m. (Note that the length of slot 0 is determined by using the address length of the calling station.) The formula for the calling station wait for net reply timeout (Twrn) is

    Twrn = Tswt (NS + 1)

    where NS is the total number of slots; one is added to include slot zero.

    The formula for the called station acknowledgment timer is

    Twan = Twrn + 2 Trw
    A.5.5.4.1.4 Slotted response example.

    The slotted response example is shown in figure A-33.



    FIGURE A-33. 2G ALE slotted responses.

    A.5.5.4.2 Star net calling protocol.

    A net address is assigned to a set of net member stations, as described in A.5.2.4.4. The slot number and address to be used by each net member are preassigned and known to all net members.

    A.5.5.4.2.1 Star net call.

    A star net call is identical to a one-to-one call, except that the called station address is a net address, as shown in figure A-34. The calling station address shall be an individual station address (not a net or other collective address).



    FIGURE A-34. Net call.
    A.5.5.4.2.2 Star net response.

    When an ALE controller receives a call that is addressed to a net address that appears in its self address memory (see A.4.3.2), it shall process the call using the same checks and timeouts as an individual call (see A.5.5.3.2). If the call is acceptable, it shall respond in accordance with A.5.5.4.1 using its assigned net member address and slot number for the net address that was called.

    A.5.5.4.2.3 Star net acknowledgment.

    A star net acknowledgment is identical to a one-to-one acknowledgment, except that the called station address is a net address.

    An ALE controller that has responded to a net call shall process the acknowledgment from the calling station in accordance with A.5.5.3.4, except that the wait-for-response timeout value shall be the Twan timeout from A.5.5.4.1.3. A TWAS acknowledgment from the calling station shall return the called ALE controller to its pre-linking state. If a TIS acknowledgment is received from the calling station, the called ALE controller shall enter the linked state with the calling station (SAM in this example), alert the operator (and network controller if present), unmute the speaker, and set a wait-for-activity timeout Twa.

    A.5.5.4.3 Star group calling protocol.

    The group calling protocol extends the power of one-to-many calling to ad hoc collections of stations that have not been preprogrammed as a net. Nothing need be known about the stations except their individual addresses and scanned frequencies. Because a group is not set up in advance, stations must be able to derive group membership and slot parameters on the fly. Group membership is limited as follows:

    A.5.5.4.3.1 Star group scanning call.

    A group address is produced by combining individual addresses of the stations that are to form the group. During a scanning call, only the first word(s) of addresses shall be sent, just as for individual or net calls. The set of unique first address words for the group members shall be sent repeatedly in rotation until the end of Tsc. These address words shall alternate between THRU and REP preambles (see figure A-35 for a sample group consisting of BOB, EDGAR, and SAM).



    FIGURE A-35. Group call.

    When group member addresses share a common first word, that word shall be sent only once during Tsc. A limit of five unique first words may be sent in rotation during Tsc.

    A.5.5.4.3.2 Star group leading call.

    During Tlc, the complete addresses of the prospective group members shall be sent, using TO preambles as usual. Up to 12 address words total are allowed for the full addresses of group members, so Tlc in a group call may last up to 24 Trw. Note in figure A-34 that when a TO word would follow another TO word, a REP preamble must be used, but when a TO follows any other word it shall remain a TO.

    A.5.5.4.3.3 Star group call conclusion.

    The optional message section and the conclusion of a star group call shall be in accordance with A.5.2.5.

    A.5.5.4.3.4 Receiving a star group call.

    Slots shall be derived for group call responses by noting the order in which individual addresses appear in the call.

    a. When an ALE controller pauses on a channel carrying a group scanning call, it will read either a THRU or a REP preamble. If the address word in this first received word matches the first word of one of its individual addresses, the ALE controller shall stay to read the leading call. Otherwise, it shall continue to read first address words until it finds:

    (In the latter two cases, the station is not being called and the ALE controller shall return to the available or linked state as appropriate.)

    b. When Tlc starts, an ALE controller potentially addressed in the scanning call shall watch for its complete address. If found, a slot counter shall be set to 1 and incremented for each address that follows it. If that address is found again (as it should be, because the address list is repeated in Tlc), the counter shall be then reset to 1, and incremented for each following address as before. The number of words in each following address shall also be noted for use in computing Tswt.

    c. The message section (if any) and the frame conclusion shall processed in accordance with A.5.5.3.2.

    In the event that an addressed ALE controller arrives on channel too late to identify the size of the called group, it will be unable to compute the correct Twan. In this situation, it shall use a default value for Twan, which is equal to the longest possible group call of twelve one-word addresses. It will, however, have computed its correct slot number because to have received its own address it must also have received the addresses that followed that self address in the leading call.

    A.5.5.4.3.5 Star group slotted responses.

    Slotted responses shall be sent and checked in accordance with A.5.5.4.1, using the derived slot numbers and the self address contained in the leading call.

    A.5.5.4.3.6 Star group acknowledgment.

    The acknowledgment in a group call handshake shall be addressed to any subset of the members originally called, and is usually limited to those whose responses were heard by the calling station. The leading call of the acknowledgment shall include the full addresses of the stations addressed, sent twice, using the same syntax as in the call (A.5.5.4.3.2).

    An ALE controller that responded to a group call shall await acknowledgment and process an incoming acknowledgment in accordance with A.5.5.3.4, with the following exceptions:

    An ALE controller that responded but was not named in the acknowledgment shall return to its pre-linking state. An ALE controller that is addressed in the acknowledgment shall proceed as follows:

    A.5.5.4.3.7 Star group call example.

    In the example group call in figure A-35, SAMUEL will respond in slot 1, with Tswt = 14 Tw (the one-word address JOE causes slot 0 to be 14 Tw). EDGAR will respond in slot 2, with Tswt = 14 + 17 Tw = 31 Tw (slot 1 is 17 Tw because of SAMUEL's two-word address). BOB will respond in slot 3, with Tswt = 48 Tw. JOE will send an acknowledgment after 62 Tw.

    A.5.5.4.3.8 Multiple self addresses in group call.

    If a station is addressed multiple times in a group call, even by different addresses, it shall properly respond to at least one address.

    NOTE: The fact that the called station has multiple addresses may not be known to the caller. In some cases, it would be confusing or inappropriate to respond to one but not another address. Redundant calling address conflicts can be resolved after successful linking, if there is a problem.

    A.5.5.4.4 Allcall protocol.

    An AllCall requests all stations hearing it to stop and listen, but not respond. The AllCall special address structure(s) (see A.5.2.4.7) shall be the exclusive member(s) of the scanning call and the leading call, and shall not be used in any other address field or any other part of the handshake. The global AllCall address shall appear only in TO words. Selective AllCalls with more than one selective AllCall address, however, shall be sent using group addressing, using THRU during the scanning call and TO during the leading call.

    An AllCall pertains to an ALE controller when it is a global AllCall, or when a selective AllCall specifies a character that matches the last character of any self address assigned to that station. Upon receipt of a pertinent AllCall, an ALE controller shall temporarily stop scanning and listen for a preset limited time, Tcc max.

    If a pertinent AllCall frame is successfully received and is concluded with a TIS, the controller shall enter the linked state, alert the operator, unmute its speaker and start a wait-for-activity timeout. If an AllCall is successfully received with a TWAS conclusion, the called controller shall automatically resume scanning and not respond (unless otherwise directed by the operator or controller).

    If a station receiving an AllCall desires to attempt to link with the calling station, the operator may initiate a handshake within the pause after a TIS conclusion. Note that in all handshakes (the initial AllCall does not constitute a handshake), the AllCall address shall not be used. To minimize possible adverse effects resulting from overuse or abuse of AllCalls, controllers shall have the capability to ignore AllCalls. Normally AllCall processing should be enabled.

    A.5.5.4.5 AnyCall protocol.

    An AnyCall is similar to an AllCall, but it instead requests responses. Use of the AnyCall special address structures is identical to that for the AllCall special address structures. Upon receipt of a pertinent AnyCall, an ALE controller shall temporarily stop scanning and examine the call identically to the procedure for AllCalls, including the Tcc max, Tm max, and Tx max limits.

    If the AnyCall is successfully received, and is concluded with TIS, the controller shall enter the linking state and automatically generate a slotted response in accordance with A.5.5.4.1 and the following special procedure:

    In this protocol, collisions are expected and tolerated. The station sending the AnyCall shall attempt to read the best response in each slot.

    Upon receipt of the slotted responses, the calling station shall transmit an ACK to any subset of stations whose responses were read, using an individual or group address. The AnyCall special address shall not be used in the acknowledgment. The caller selects the conclusion of its ACK to either maintain the link for additional interoperation and traffic with the responders (TIS), or return everyone to scan (TWAS), as appropriate to the caller's original purpose.

    An ALE controller that responded to an AnyCall shall await and process the acknowledgment in accordance with A.5.5.4.3.6.

    To minimize possible adverse effects resulting from overuse or abuse of AnyCalls, controllers shall have the capability to ignore AnyCalls. Normally AnyCall processing should be enabled.

    A.5.5.4.6 Wildcard calling protocol.

    Wildcard addresses shall be the exclusive members of a calling cycle in a call, and shall not be used in any other address sequence in the ALE frame or handshake. The span (number of cases possible) of the wildcard(s) used should be minimized to only the essential needs of the user(s).

    Calls to wildcard addresses that conclude with TWAS shall be processed identically to the AllCall protocol.

    Responses to wildcard calls that conclude with TIS shall be sent in pseudorandomly-selected slots in accordance with the AnyCall protocol.

    As in both the AllCall and AnyCall, the controller shall be programmable to ignore wildcard calls, but wildcard call processing should normally be enabled.

    A.5.6. ALE control functions (CMDs other than AMD, DTM, and DBM).

    In addition to automatically establishing links, stations shall have the capability to transfer information within the orderwire, or message, section of the frame. This section describes these messages, including data, control, error checking, networking, and special purpose functions. Table A-XVI provides a summary of the CMD functions.

    NOTE: For critical orderwire messages that require increased protection from interference and noise, several ALE techniques are available. Any message may be specially encoded off-line and then transmitted using the full 128 ASCII CMD data DTM mode (which also accepts random data bits). Larger blocks of information may be Golay FEC coded and deeply interleaved using the CMD DBM mode. Both modes have an automatic repeat request (ARQ) error-control capability. Integrity of the data may be ensured using the CMD cyclic redundancy check (CRC) mode (see A.5.6.1). In addition, once a link has been established, totally separate equipment, such as heavily coded and robust modems, may be switched onto the rf link in the normal circuit (traffic-bearing) mode.

    TABLE A-XVI. Summary of CMD functions.
    First Character Second Character Function
    Any of the extended-64 character set AMD
    " 1100000 Advanced LQA
    a 1100001 LQA
    b 1100010 Data block analysis
    c 1100011 Channels
    d 1100100 DTM
    f 1100110 Frequency
    m 1101101 Mode selection commands
    a1100001 Analog port Selection
    c1100011 Crypto negotiation
    d1100100 Data port selection
    n1101110 Modem negotiation
    q1110001 Digital squelch
    n 1101110 Noise report
    p 1110000 Power control
    r 1110010 LQA report
    t 1110100 Scheduling commands
    a1100001 Adjust slot width
    b1100010 Station busy
    c1100011 Channel busy
    d1100100 Set dwell time
    h1101000 Halt and wait
    l1101100 Contact later
    m1101101 Meet me
    n1101110 Poll operator (default NAK)
    o1101111 Request operator ACK
    p1110000 Schedule periodic function
    q1110001 Quiet contact
    r1110010 Respond and wait
    s1110011 Set sounding interval
    t1110100 Tune and wait
    w1110111 Set slot width
    x1111000 Do not respond
    y1111001 Year and date
    z1111010 Zulu time
    v 1110110c 1100011 Capabilities
    s1110011 Versions
    x 1111000 CRC*
    y

    z

    {

    1111001

    1111010

    1111011

    CRC*

    CRC*

    CRC*

    |1111100 User-unique functions
    ~1111110 Time exchange
    *(16-bit CRC overflows into the two least-significant bits of the first two character)

    A.5.6.1 CRC.

    This special error-checking function is available to provide data integrity assurance for any form of message in an ALE call.

    NOTE: The CRC function is optional, but mandatory when used with the DTM or DBM modes.

    The 16-bit frame check sequence (FCS) and method as specified by FED-STD 1003 shall be used herein. The FCS provides a probability of undetected error of 2-16, independent of the number of bits checked. The generator polynomial is

    X16 + X12 + X5 + 1

    and the sixteen FCS bits are designated

    (MSB) X15, X14, X13, X12...X1, X0 (LSB)

    The ALE CRC is employed two ways: within the DTM data words, and following the DBM data field, described in paragraphs A.5.7.3 and A.5.7.4, respectively. The first, and the standard, usages are described in this section.

    The CMD CRC word shall be constructed as shown in table A-XVII. The preamble shall be CMD (110) in bits P3 through P1 (W1 through W3). The first character shall be "x" (1111000), "y" (1111001), "z" (1111010), or "{" (1111011) in bits C1-7 through C1-1 (W4 through W10). Note that four identifying characters result from FCS bits X15 and X14 which occupy C1-2 and C1-1 (W9 and W10) in the first character field respectively. The conversion of FCS bits to and from ALE CRC format bits shall be as described in table A-XVII where X15 through X0 correspond to W9 through W24.

    The CMD CRC message should normally appear at the end of the message section of a transmission, but it may be inserted within the message section (but not within the message being checked) any number of times for any number of separately checked messages, and at any point except the first word (except as noted below). The CRC analysis shall be performed on all ALE words in the message section that precede the CMD CRC word bearing the FCS information, and which are bounded by the end of the calling cycle, or the previous CMD CRC word, whichever is closest. The selected ALE words shall be analyzed in their non-redundant and unencoded (or FEC decoded) basic ALE word (24-bit) form in the bit sequence (MSB) W1, W2, W3, W4...W24 (LSB), followed by the unencoded bits W1 through W24 from the next word sent (or received), followed by the bits of the next word, until the first CMD CRC is inserted (or found). Therefore, each CMD CRC inserted and sent in the message section ensures the data integrity of all the bits in the previous checked ALE words, including their preambles. If it is necessary to check the ALE words in the calling cycle (TO) preceding the message section, an optional calling cycle CMD CRC shall be used as the calling cycle terminator (first FROM or CMD), shall therefore appear first in the message section, and shall analyze the calling cycle words in their simplest (Tc), nonredundant and nonrotated form. If it is necessary to check the words in a conclusion (TIS or TWAS), an optional conclusion CRC shall directly precede the conclusion portion of the call, shall be at the end of the message section, and shall itself be directly preceded by a separate CMD CRC (which may be used to check the message section or calling cycle, as described herein). Stations shall perform CRC analysis on all received ALE transmissions and shall be prepared to compare analytical FCS values with any CMD CRC words which may be received. If a CRC FCS comparison fails, an ARC (or operator initiated) or other appropriate procedure may be used to correct the message.

    TABLE A-XVII. Cyclic redundancy check structure.


    A.5.6.2 Power control (optional).

    The power control orderwire function is used to advise parties to a link that they should raise or lower their rf power for optimum system performance. The power control CMD word format shall be as shown in figure A-36. The KP control bits shall be used as shown in table XVIII.
    3
    7
    3
    6
    5

    CMD
    1110000

    ('p': power control)


    KP1-3

    Power

    (reserved)

    FIGURE A-36. Power control CMD format.

    TABLE A-XVIII. Power control CMD bits (KP1-3).
    BitValue Meaning
    KP3 (MSB)

    KP2

    KP1 (LSB)

    1

    0

    1

    0

    1

    0

    Request to adjust power

    Report of current power level

    Relative Power (in dB)

    Absolute Power (in dBW)

    Relative Power (dB) is positive

    Relative Power (dB) is negative

    The procedure shall be:

    a. When KP3 is set to 1, the power control command is a request to adjust the power from the transmitter. If KP2 is 1, the adjustment is relative to the current operating power, i.e., to raise (KP1 = 1) or lower (KP1 = 0) power by the number of dB indicated in the relative power field. If KP2 is 0, the requested power is specified as an absolute power in dBW.

    b. When KP3 is set to 0, the power control command reports the current power output of the transmitter, in dB relative to nominal power if KP2 is 1, or in absolute dBW if KP2 is 0.

    c. KP1 shall be set to 0 whenever KP2 is 0.

    d. Normally, a station receiving a power control request (KP3 = 1) should approximate the requested effect as closely as possible, and respond with a power report (KP3 = 0) indicating the result of its power adjustment.

    A.5.6.3 Channel related functions.

    The channel related functions are defined in the following subparagraphs.

    A.5.6.3.1 Channel designation.

    When two or more stations need to explicitly refer to channels or frequencies other than the one(s) in use for a link, the following encodings shall be used. A frequency is designated using binary-coded-decimal (BCD). The standard frequency designator is a five-digit string (20 bits), in which the first digit is the 10 megahertz (MHz) digit, followed by 1 MHz, 100 kilohertz (kHz), 10 kHz, and 1 kHz digits. A frequency designator is normally used to indicate an absolute frequency. When a bit in the command associated with a frequency designator indicates that a frequency offset is specified instead, the command shall also contain a bit to select either a positive or a negative frequency offset.

    A.5.6.3.2 Frequency designation.

    A channel differs from a frequency in that a channel is a logical entity that implies not only a frequency (or two frequencies for a full-duplex channel), but also various operating mode characteristics, as defined in A.4.3.1. As in the case of frequency designators, channels may be specified either absolutely or relatively. In either case, a 7-bit binary integer shall be used that is interpreted as an unsigned integer in the range 0 through 127. Bits in the associated command shall indicate whether the channel designator represents an absolute channel number, a positive offset, or a negative offset.

    a. The frequency select CMD word shall be formatted as shown in figure A-37. A frequency designator (in accordance with A.5.6.3.1) is sent in a DATA word immediately following the frequency select CMD; bit W4 of this DATA word shall be set to 0, as shown.
    3
    7
    6
    4
    4
    CMD1100110

    ('f': frequency)

    Control100 Hz 10 Hz
    3
    1
    4
    4
    4
    4
    4


    DATA


    0
    Frequency Designator
    10 MHz 1 MHz100 kHz 10 kHz1 kHz

    FIGURE A-37. Frequency select CMD format.

    b. The 100 Hz and 10 Hz fields in the frequency select CMD word contain BCD digits that extend the precision of the standard frequency designator. These digits shall be set to 0 except when it is necessary to specify a frequency that is not an even multiple of 1 kHz (e.g., when many narrowband modem channels are allocated within a 3 kHz voice channel).

    c. The control field shall be set to 000000 to specify a frequency absolutely, to 100000 to specify a positive offset, or to 110000 to specify a negative offset.

    d. A station receiving a frequency select CMD word shall make whatever response is required by an active protocol on the indicated frequency.

    A.5.6.3.3 Full-duplex independent link establishment (optional).

    Full duplex independent link establishment is an optional feature; however, if this option is selected the transmit and receive frequencies for use on a link shall be negotiated independently as follows:

    a. The caller shall select a frequency believed to be propagating to the distant station (the prospective responder) and places a call on that frequency. The caller embeds a frequency select CMD word in the call to ask the responder to respond on a frequency chosen for good responder-to-caller propagation (probably from sounding data in the caller's LQA matrix).

    b. If the responder hears the call, it shall respond on the second frequency, asking the caller to switch to a better caller-to-responder frequency by embedding a frequency select CMD word in its response (also based upon sounding data).

    c. The caller shall send an acknowledgment on the frequency chosen by the responder (the original frequency by default), and the full duplex independent link is established.

    A.5.6.3.4 LQA polling (optional).

    See MIL-STD-187-721.

    A.5.6.3.5 LQA reporting (optional).

    See MIL-STD-187-721.

    A.5.6.3.6 LQA scan with linking (optional).

    See MIL-STD-187-721.

    A.5.6.3.7 Advanced LQA (optional).

    See MIL-STD-187-721.

    A.5.6.4 Time-related functions.

    A.5.6.4.1 Tune and wait.

    The CMD tune and wait special control function directs the receiving station(s) to perform the initial parts of the handshake, up through tune-up, and wait on channel for further instructions during the specified time limit. The time limit timer is essentially the WRTT as used in net slotted responses where its value Twrn is set by the timing information in the special control instruction, and it starts from the detected end of the call. The CMD tune and wait instruction shall suppress any normal or preset responses. Except for the tune-up itself, the receiving station(s) shall make no additional emissions, and they shall quit the channel and resume scan if no further instructions are received.

    NOTE: This special control function enables very slow tuning stations, or stations that must wait for manual operator interaction, to effectively interface with automated networks.

    The CMD tune and wait shall be constructed as follows and as shown in table A-XIX. The preamble shall be CMD (110) in bits P3 through P1 (W1 through W3). The first character (C1) shall be "t" (1110100) in bits C1-7 through C1-1 (W4 through W10) and "t" (1110100) in bits C2-7 through C2-1 (W11 through W17), for "time, tune-up." The "T" time bits TB7 through TB1 (W18 through W24) shall be values selected from table A-XX, and limited as shown in table A-XXI. The lowest value (00000) shall cause the tuning to be performed immediately, with zero waiting time, resulting in immediate return to normal scan after tuning.

    A.5.6.4.2 Scheduling commands.

    These special control functions permit the manipulation of timing in the ALE system. They are based on the standard "T" time values, presented in table A-XX, which have the following ranges based on exact multiples of Tw (130.66...ms) or Trw (392 ms).

    There are several specific functions that utilize these special timing controls. All shall use the CMD (110) preamble in bits P3 through P1 (W1 through W3). The first character is "t" (1110100) for "time." The second character indicates the function as shown in table A-XXI. The basic structure is the same as in table A-XIX.

    TABLE A-XIX. Tune and wait structure.
    Tune and Wait Bits Word Bits
    CMD

    Preamble

    MSB

    LSB

    P3 = 1

    P2 = 1

    P1 = 0

    MSBW1

    W2

    W3

    First

    Character

    "t"

    MSB




    LSB

    C1-7 = 1

    C1-6 = 1

    C1-5 = 1

    C1-4 = 0

    C1-3 = 1

    C1-2 = 0

    C1-1 = 0

    W4

    W5

    W6

    W7

    W8

    W9

    W10

    Second

    Character

    "t"

    MSB




    LSB

    C2-7 = 1

    C2-6 = 1

    C2-5 = 1

    C2-4 = 0

    C2-3 = 1

    C2-2 = 0

    C2-1 = 0

    W11

    W12

    W13

    W14

    W15

    W16

    W17

    Time Bits

    "T"

    MSB




    LSB

    TB7

    TB6

    TB5

    TB4

    TB3

    TB2

    TB1







    LSB
    W18

    W19

    W20

    W21

    W22

    W23

    W24


    NOTES:
    1. CMD tune and wait first two characters are "t" (1110100) and "t" (1110100) for "time tune-up."
    2. Time bits TB7 through TB1 from table A-XX.

    TABLE A-XX. Time values.
    MULTIPLIER: MSBs
    MSB

    TB7

    (W18)

    TB6

    (W19)

    Exact

    increment

    Approximate

    increment
    Approximate

    range

    of "T" values

    00 Tw 130.66 . . ms
    1/8 second
    0 - 4 seconds
    01 3 Trw 1176 ms
    1 second
    0 - 36 seconds
    10 153 Trw 59.976 sec
    1 minute
    0 - 31 minutes
    11 9184 Trw 60.002min
    1 hour
    0 - 29 hours
    INDEX: Least significant Bits (LSBs)
    TB5

    (W20)

    TB4

    (W21)

    TB3

    (W22)

    TB2

    (W23)

    LBS

    TB1

    (W24)

    INDEX

    VALUE

    "T"

    VALUE

    FOR

    MSB=00

    "T"

    VALUE

    FOR

    MSB=01

    "T"

    VALUE

    FOR

    MSB=10

    "T"

    VALUE

    FOR

    MSB=11

    00 00 00 0(1)0 00
    00 00 11 130.66

    ms

    1.176 s1.00 min 1.00 hr
    00 01 02 261.33

    ms

    2.352 s2.00 min 2.00 hr
    00 01 13 392.0 ms 3.528 s3.00 min 3.00 hr
    00 10 04 523.66

    ms

    4.204 s 4.00 min4.00 hr
    00 10 15 653.33

    ms

    5.880 s5.00 min 5.00 hr
    11 10 129 3789.3

    ms

    34.10 s29.0 min 29.0 hr
    11 11 030 3920.0

    ms

    35.28 s30.0 min (3)
    11 11 131 4050.7

    ms

    36.46 s31.0 min (2)
    NOTES:
    1. The minimum value "0" (TB = 0000000) is interpreted as "do immediately" if a delay, or "zero size" if a time width, as specified in usage.
    2. The maximum value "127" (TB = 1111111) is interpreted as "do it at time or date following," as specified in next CMD.
    3. The next maximum value "126" (TB = 1111110) is interpreted as "indefinite time," unlimited except by other CMD or timeout protocol.

    TABLE A-XXI. Time-related CMD functions.

    Identification
    First

    Character

    Second

    Character


    Function
    Adjust Slot Width"t" "a" (1100001) Add T to width of all slots for this response. TB=0, normal. TB7=0 as 36 second limit.
    Halt and Wait"t" "h" (1101000) Stop scan on channel, do not tune or respond, wait T for instruction; quit and resume scan if nothing. TB=0, quit after call. TB7=0 as 36 second limit.
    Operator NAK"t" "n" (1101110) Same as "t,o" operator ACK, except that at T, if no input, automatic tune-up and respond NAK (TIS), in slots if any. TB=0, NAK now.
    Operator ACK"t" "o" (1101111) Stop scan, alert operator to manually input ACK (or NAK), which causes tune-up (if needed) and ACK response TWAS, or TIS; if no input by operator by T, simply quit. TB=0, ACK now. TB7=0 as 36 second time limit. TB=1111111, do at date/time following.
    Respond and Wait"t" "r" (1110010) Stop scan, tune-up and respond as normal, wait T for instructions, quit and resume scan if nothing. TB=0, quit after response. TB7=0 as 36 second limit. TB=1111111, do at date/time following.
    Tune and Wait"t" "t" (1110100) Stop scan, tune-up, do not respond, wait T for Instructions, quit and resume scan if nothing. TB=0, quit after tune-up. TB7=0 as 36 second limit.
    Width of Slots"t" "w" (1110111) Set all slots to T wide for this response. TB=0, no responses. TB7=0 as 36 second limit.

    NOTES:
    1. Preamble is CMD (110).
    2. First character is "t" (1110100) for all.
    3. Third-character field is binary bits TB7 through TB1 (W18 through W24), designating a time interval "T" as a standard value in table A-XX.
    4. When the optional UUF is implemented, the STAY command function is required.
    5. This second ASCII character will vary, depending on the resulting binary value.

    A.5.6.4.3 Time exchange word formats.

    The mandatory time protocols employ the following three types of ALE words: (1) command words, (2) coarse time words, and, (3) authentication words, in the formats listed below.

    A.5.6.4.3.1 Command words.

    Time exchange command words Time Is and Time Request that are used to request and to provide time of day (TOD) data, shall be formatted as shown in figure A-38. The three most-significant bits (W1-3) shall contain the standard CMD preamble (110). The next seven bits (W4-10) shall contain the ASCII character '~'(1111110), indicating the magnitude of time uncertainty at the sending station in accordance with A.5.6.4.6.

    A.5.6.4.3.2 Time Is command.

    The Time Is command word carries the fine time current at the sending station as of the start of transmission of the word following the Time Is command word, and is used in protected time requests and all responses. In a Time Is command word, the seconds field shall be set to the current number of seconds elapsed in the current minute intervals which have elapsed in the current second (0-24). The time quality shall reflect the sum of the uncertainty of the local time and the uncertainty of the time of transmission of the Time Is command, in accordance with table A-XXII and A.5.6.4.6. When a protocol requires transmission of the Time Is command word, but no time value is available, a NULL Time Is command word shall be sent, containing a time quality of 7 and the seconds and ticks fields both set to all 1s.

    A.5.6.4.3.3 Time Request command.

    The Time Request command word shall be used to request time when no local time value is available, and is used only in non-protected transmissions. In a Time Request command word, time quality shall be set to 7, the seconds field to all 1s, and the ticks field set to 30 (11110).

    A.5.6.4.3.4 Other encodings.

    All encodings of the seconds and ticks fields not specified here are reserved, and shall not be used until standardized.

    A.5.6.4.4 Coarse time word.

    Coarse time words shall be formatted as shown in figure A-39, and shall contain the coarse time current as of the beginning of that word.

    Time Service Example
    Date=8 May
    Time=15:57:34:12
    Time Quality=4
    3
    7
    3
    6
    5
    CMDTime Exchange Time QualitySeconds40 ms ticks
    1101111110100 10001000011
    "TIME IS" Command

    FIGURE A-38. Time exchange CMD word.

    A.5.6.4.5 Authentication word.

    Authentication words, formatted as shown in figure A-39, shall be used to authenticate the times exchanged using the time protocols. The 21-bit authenticator shall be generated by the sender as follows:

    a. All 24-bit words in the time exchange message preceding the authentication word (starting with the Time Is or Time Request command word which begins the message) shall be exclusive-or'd.

    b. If the message to be authenticated is in response to a previous time exchange message, the authenticator from that message shall be exclusive-or'd with the result of (1).

    c. The 21 least significant bits of the final result shall be used as the authenticator.

    A.5.6.4.6 Time quality.

    Every time exchange command word transmitted shall report the current uncertainty in TOD at the sending station, whether or not time is transmitted in the command word. The codes listed in table A-XXII shall be employed for this purpose. The time uncertainty windows on the table are upper bounds on total uncertainty (with respect to coordinated universal time).

    TABLE A-XXII. Time quality.
    Time Quality Code
    Time Uncertainty Window
    0
    none
    1
    20 ms
    2
    100 ms
    3
    500 ms
    4
    2 s
    5
    10 s
    6
    60 s
    7
    unbounded
    NOTE: Time quality "0" shall be used only by UTC time standard stations.
    Time Service Example
    Date = 8 May
    Time = 15:57:34:12
    Time Quality = 4
    3
    1
    4
    5
    11
    DATA0 MonthDay Minute
    0000 010101000 011101111101
    Coarse Time Word
    3
    21
    REP Authenticator
    111 110101110011111111110
    Authenticator Word
    (over CMD and Coarse Time Words)

    FIGURE A-39. Coarse time and authentication words.

    For example, an uncertainty of ±6 seconds is 12 seconds total and requires a transmitted time quality value of 6. Stations shall power up from a cold start with a time quality of 7. Time uncertainty is initialized when time is entered (see B.5.2.2.1) and shall be maintained thereafter as follows:

    a. The uncertainty increases at a rate set by oscillator stability (e.g., 72 ms per hour with a ±10 parts per million (ppm) time base).

    b. Until the uncertainty is reduced upon the acceptance of time with less uncertainty from an external source after which the uncertainty resumes increasing at the above rate.

    A station accepting time from another station shall add its own uncertainty due to processing and propagation delays to determine its new internal time uncertainty. For example, if a station receives time of quality 2, it adds to the received uncertainty of 100 ms (±50 ms) its own processing delay uncertainty of, say ±100 ms, and a propagation delay bound of ±35 ms, to obtain a new time uncertainty of ±185 ms, or 370 ms total, for a time quality of 3. With a ±10 ppm time source, this uncertainty window would grow by 72 ms per hour, so after two hours, the uncertainty becomes 514 ms, and the time quality has dropped to 4. If a low-power clock is used to maintain time while the rest of the unit is powered off, the quality of this clock shall be used to assign time quality upon resumption of normal operation. For example, if the backup clock maintains an accuracy of ±100 ppm under the conditions expected while the station is powered off, the time uncertainty window shall be increased by 17 seconds per day. Therefore, such a radio, which has been powered-off for much over three days, shall not be presumed to retain even coarse sync, despite its backup clock, and may require manual entry of time.

    A.5.6.5 Mode control functions (optional).

    If any of these features are selected, however, they shall be implemented in accordance with this standard. Many of the advanced features of an ALE controller are "modal" in the sense that when a particular option setting is selected, that selection remains in effect until changed or reset by some protocol event. The mode control CMD is used to select many of these operating modes, as described in the following paragraphs. The CMD word shall be formatted as shown in figure A-40. The first character shall be 'm' to identify the mode control command; the second character identifies the type of mode selection being made; the remaining bits specify the new setting for that mode.
    3
    7
    7
    7

    CMD
    1101101

    ('m': mode control)


    Mode ID

    Mode Selection

    FIGURE A-40. Mode control CMD format.

    A.5.6.5.1 Modem negotiation and handoff.

    An ALE data link can be used to negotiate a modem to be used for data traffic by exchanging modem negotiation messages. A modem negotiation message shall contain one modem selection command.

    NOTE: This function may best be implemented in a high frequency node controller (HFNC) to avoid retrofit to existing ALE controllers, and for the greater flexibility inherent in network management information bases.

    A.5.6.5.1.1 Modem selection CMD.

    The modem selection CMD word shall be formatted as shown in figure A-41, and may be followed by one or more DATA words, as described below. The defined modem codes are listed in table A-XXIII. Codes not defined are reserved, and shall not be used until standardized.
    3
    7
    7
    7

    CMD
    1101101

    ('m': mode control)

    1101110

    ('n': modem select)


    Modem Code

    FIGURE A-41. Modem selection CMD format.
    A.5.6.5.1.2 Modem negotiating.

    Modem negotiating shall employ modem negotiation messages in the following protocol:

    a. The station initiating the negotiation will send a modem selection CMD word containing the code of the modem it wants to use.

    b. The responding station(s) may either accept this modem selection or suggest alternatives. A station accepting a suggested modem shall send a modem selection CMD word containing the code of that modem.

    c. A station may negotiate by sending a modem selection CMD word containing all 1s in the modem code field, followed by one or more DATA words containing the codes of one or more suggested modems. Modem codes shall be listed in order of preference in the DATA word(s). Unused positions in the DATA word(s) shall be filled with the all 1s code.

    d. The negotiation is concluded when the most recent modem negotiation message from all participating stations contains an identical modem selection CMD word with the same modem code (not all 1s). When this occurs, the station that initiated the negotiation will normally begin sending traffic using the selected modem.

    TABLE A-XXIII. Modem codes.
    Code Modem Type
    0000000 (Reserved)
    0000001 ALE modem
    0000010 Serial-tone HF data modem (MIL-STD-188-110)
    0000011 16-tone DPSK HF data modem (MIL-STD-188-110)
    0000100 39-Tone HF data modem (MIL-STD-188-110)
    0000101 ANDVT
    0000110 FSK 170 Hz shift (MIL-STD-188-110)
    0000111 FSK 850 Hz shift (MIL-STD-188-110)
    Short intlv (010xxxx) long intlv STANAG 4285
    0100000 0101000 75 b/s
    0100001 0101001 150 b/s
    0100010 0101010 300 b/s
    0100011 0101011 600 b/s
    0100100 0101100 1200 b/s
    0100101 0101101 2400 b/s
    0100110 0101110 4800 b/s
    (011xxxx) STANAG 4529:
    0110000 0111000 75 b/s
    0110001 0111001 150 b/s
    0110010 0111010 300 b/s
    0110011 0111011 600 b/s
    0110100 0111100 1200 b/s
    0110101 0111101 2400 b/s
    0110110 0111110 4800 b/s
    1111111Reserved to indicate no modem code. (All others reserved until defined)

    A.5.6.5.2 Crypto negotiation and handoff.

    When crypto negotiation and handoff are required, the following applies:

    a. An ALE data link can also be used to negotiate an encryption device to be used for voice or data traffic by exchanging crypto negotiation messages. The crypto selection CMD word is formatted as shown in figure A-42. The defined crypto codes are listed in table A-XXIV. Codes not defined are reserved, and shall not be used until standardized.

    NOTE: This function may best be implemented in an HFNC to avoid retrofit to existing ALE controllers, and for the greater flexibility inherent in network management information bases.
    3
    7
    7
    7

    CMD
    1101101

    ('m': mode control)

    1100011

    ('c': crypto select)


    Crypto Code

    FIGURE A-42. Crypto selection CMD format.

    TABLE A-XXIV. Crypto codes.
    CodeCrypto Type
    0000000

    1111111

    No encryption

    Reserved to indicate no crypto code

    (All others reserved until defined)

    b. Crypto negotiation shall employ crypto negotiation messages in the protocol described above for modem negotiation.

    A.5.6.6 Capabilities reporting functions.

    A.5.6.6.1 Version CMD (mandatory).

    The version CMD function is used to request ALE controller version identification. The first character is 'v' to indicate the version family of ALE CMD word functions. The second character shall be set to 's' to select a summary report.

    NOTE: The capabilities function in A.5.6.6.2 is a variant of this function that provides more detailed information.

    a. The response to a version CMD is a printable ASCII message in manufacturer-specific format that indicates a manufacturers' identification, the version(s) of hardware, operating firmware and software, and/or management firmware and software of the responding ALE controller, as requested by control bits KVC1-3 of the version CMD format (see figure A-43 and table A- XXV).
    3
    7
    7
    3
    4

    CMD
    1110110

    ('v': version CMD)

    1110011

    ('s': summary)

    Comps

    (KVC)

    Formats

    (KVF)

    FIGURE A-43. Version CMD format.

    TABLE A-XXV. Component selection.
    BitComponent whose version is requested when bit set to 1
    KVC3 (MSB)

    KVC2

    KVC1 (LSB)

    ALE controller hardware

    ALE controller operating firmware

    ALE controller network management firmware (i.e., HNMP)

    b. The requesting station specifies acceptable formats for the response in control bits KVF1-4 in accordance with table A-XXVI. A controller responding to a version function shall attempt to maximize the utility of its response and:

  • (1) Shall report the version(s) of all of the components requested by the KVC control bits that are present in the controller.
  • (2) Shall use the ALE message format that represents the highest level of mutual capability of itself and the requesting station by comparing the message types that it can generate with those desired by the requesting station, and selecting the message type in the intersection of these two sets that correspond to the highest-numbered KFV bit.
  • TABLE A-XXVI. Format selection.
    Bit Reporting format desired when bit set to 1
    KVF4 (MSB)

    KVF3

    KVF2

    KVF1 (LSB)

    Reserved (always set to 0)

    DBM

    DTM

    AMD Message

    A.5.6.6.2 Capabilities function. (mandatory).

    The capabilities function is used to obtain a compact representation of the features available in a remote ALE controller. This function uses a variant of the version CMD word, as shown in figures A-44 and A-45.

    A.5.6.6.2.1 Capabilities query.

    The capabilities query, shown in figure A-44, consists of a single ALE CMD word. The second character position shall be set to 'c' to select a full capabilities report (rather than a summary as in the version CMD). The third character position shall be set to 'q' in a capabilities query to request a capabilities report.
    3
    7
    7
    7

    CMD
    1110110

    ('v': version CMD)

    1100011

    ('c': capability)

    1110001

    ('q': query)

    FIGURE A-44. Capabilities query CMD format.
    A.5.6.6.2.2 Capabilities report CMD.

    The capabilities report shall consist of a CMD word followed by five DATA words, as shown in figure A-45. The second character position of the capabilities report CMD word shall be set to 'c' and the third character position shall be set to 'r'. (The DATA preamble in the second and fourth DATA words shall be replaced by REP for transmission, as required by the ALE protocol).
    3
    7
    7
    7
    CMD
    1110110

    ('v': version CMD)
    1100011

    ('c': capability)
    1110010

    ('r': report)
    3
    5
    8
    8
    DATA
    Scan Rate

    (SR1-5)
    Channels Scanned

    (CS1-8)
    Max Tune Time

    (TT1-8)
    3
    6
    7
    8
    DATA
    LP Time

    (LPT1-6)
    ALE Protocols

    (VAP1-7)
    ALQA

    (ALQA1-8)
    3
    8
    8
    5
    DATA
    Orderwire

    (OW1-8)
    Reserved
    Reserved
    3
    21
    DATA
    Scheduling

    (SCH1-21)

    FIGURE A-45. Capabilities report CMD and DATA format.
    A.5.6.6.2.3 Data format.

    The format of the DATA words in a capabilities report is constant, regardless of the capabilities reported, to simplify the software that implements the capabilities command. The data fields of the capabilities report shall be encoded in accordance with tables A-XXVII, A-XXVIII, and A-XXIX. The values encoded shall represent the current operational capabilities of the responding ALE controller, i.e., the timing or functions currently programmed. All timing fields shall be encoded as unsigned integers.

    TABLE A-XXVII. Capabilities report data fields (ALE timing).

    Group

    Field

    Value

    Units
    Parameter from

    table A-XV "Timing"

    ALE TimingSR1-5

    CS1-8

    TT1-8

    TTA1-4

    TWA1-4

    TWT1-3

    Scan rate

    Chan. scanned

    Max tune time

    Turnaround time

    Activity timeout Listen time

    Channels/s

    100 ms

    100 ms

    log2 s

    1 s

    1/Td

    C

    Tt

    Tta

    Twa*

    Twt


    * Twa=log2 n where n is the number of seconds of no detected activity before timeout.

    TABLE A-XXVIII. Capabilities report data fields (mode settings).
    GroupBit Set to 1 if and only if (iff) Cross Ref: MIL-STD
    ALE

    Protocols

    VAP7 (MSB)

    VAP6

    VAP5

    VAP4

    VAP3

    VAP2

    VAP1 (LSB)

    Accepting ALL calls

    Accepting ANY calls

    Accepting AMD 2msgs

    Accepting DTM msgs

    Accepting DBM msgs

    DTM capabilities

    DBM capabilities

    188-141 (Allcalls)

    188-141 (AnyCalls)

    188-141 (AMD mode)

    188-141 (DTM mode)

    188-141 (DBM mode)

    188-141 (DTM mode)

    188-141 (DBM mode)

    LP LevelsLPL5 (MSB)

    LPL4

    LPL3

    LPL2

    LPL1 (LSB)

    Capable of other LP

    Capable of AL-4 LP

    Capable of AL-3 LP

    Capable of AL-2 LP

    Capable of AL-1 LP


    188-141 Appendix B

    188-141 Appendix B

    188-141 Appendix B

    188-141 Appendix B

    Time ExchangeLPT6 (MSB)

    LPT5

    LPT4

    LPT3

    LPT2

    LPT1 (LSB)

    Acting as time server

    Active time acq. enable

    Passive time acq. enable

    Will send time broadcasts

    Time iteration capable

    Precision time capable

    188-141 (Time service response, Time service response (non-protected)

    188-141 (Active time acquisition (protected), Active time acquisition (non-protected)

    188-141 (Passive time acquisition)

    188-141 (Time broadcast)

    (not yet standardized)

    (not yet standardized)

    TABLE A-XXIX. Capabilities report data field (feature capabilities).
    GroupBit Set to 1 iff Feature Implemented Cross Ref: MIL-STD (paragraph)
    Polling PP5 (MSB)

    PP4

    PP3

    PP2

    PP1 (LSB)

    Full Net Poll

    Full Group Poll

    Channel Scan CMD

    LQA Report

    Local Noise Report

    187-721 (Full Net Poll)

    187-721 (Full Group Poll)

    187-721 (Two Station- Multiple Channel Polling)

    187-721 (LQA Report Protocol)

    188-141 (Local Noise Report)

    ALQAALQA8 (MSB)

    ALQA7

    ALQA6

    ALQA5

    ALQA4

    ALQA3

    ALQA2

    ALQA1 (LSB)

    Reserved (always set to 0)

    ALQA SINAD

    ALQA PBER

    ALQA AI

    ALQA SD

    ALQA EFI

    ALQA AVQ

    ALQA ADC


    187-721 (SINAD and PBER)

    187-721 (SINAD and PBER)

    187-721 (Articulation Index)

    187-721 (Spectral Distortion)

    187-721 (Error-free Interval)

    187-721 (Achievable Voice Quality)

    187-721 (Available Data Capacity)

    OrderwireOW8 (MSB)

    OW7

    OW6

    OW5

    OW4

    OW3

    OW2

    OW1 (LSB)

    Frequency Select CMD

    Channel Select CMD

    Modem Negotiation

    Crypto Negotiation

    Analog Port Selection

    Data Port selection

    Digital Squelch

    Power Control

    187-721 (Frequency Select Command)

    (not yet standardized)

    188-141 (Modem Negotiation and Handoff)

    188-141 (Crypto Negotiation and handoff)

    187-721 (Analog Port Selection)

    187-721 (Data Port Selection)

    187-721 (Digital Squelch)

    188-141 (Power Control)

    SchedulingSCH21 (MSB)

    SCH20

    SCH19

    SCH18

    SCH17

    SCH16

    SCH15

    SCH14

    SCH13

    SCH12

    SCH11

    SCH10

    SCH9

    SCH8

    SCH7

    SCH6

    SCH5

    SCH4

    SCH3

    SCH2

    SCH1 (LSB)

    Reserved (always set to 0)

    Adjust Slot Width

    Station Busy

    Channel Busy

    Set Dwell Time

    Halt and Wait

    Contact Later

    Meet Me

    Poll Operator (default NAK)

    Request Operator ACK

    Schedule Periodic Function

    Quiet Contact

    Respond and Wait

    Set Sounding Interval

    Tune and wait

    Set Slot Width

    Year and Date

    Zulu Time

    Do Not Respond

    Reserved (always set to 0)

    Reserved (always set to 0)


    187-721 (Adjust Slot Width)

    187-721 (Station Busy)

    187-721 (Channel Busy)

    187-721 (Set Dwell Time)

    187-721 (Halt and Wait)

    187-721 (Contact Later)

    187-721 (Meet Me)

    187-721 (Poll Operator(default NAK))

    187-721 (Request Operator ACK)

    187-721 (Schedule Periodic Function)

    187-721 (Quiet Contact)

    187-721 (Respond and Wait)

    187-721 (Set Sounding Interval)

    187-721 (Tune and Wait)

    187-721 (Set Slot Width)

    187-721 (Year and Date)

    187-721 (Zulu Time)

    188-141 (Do Not Respond)

    A.5.6.7 Do not respond CMD.

    When an ALE controller receives this CMD in a transmission, it shall not respond unless a response is specifically required by some other CMD in the transmission (e.g., an LQA request or a DTM or DBM with ARQ requested). In a Do Not Responds CMD, no three-way ALE handshake needs to be completed.

    A.5.6.8 Position report (optional).

    See MIL-STD-187-721.

    A.5.6.9 User unique functions (UUFs).

    UUFs are for special uses, as coordinated with specific users or manufacturers, which use the ALE system in conjunction with unique, nonstandard, or non-ALE, purposes. There are 16384 specific types of CMD UUF codes available, as indicated by a 14-bit (or two-character) unique index (UI). Each unique type of special function that employees a UUF shall have a specific UI assigned to it to ensure interoperability, compatibility, and identification. The UI shall be assigned for use before any transmission of the UUF or the associated unique activity, and the ALE UUF shall always include the appropriate UI when sent.

    The UUF shall be used only among stations that are specifically addressed and included within the protocol, and shall be used only with stations specifically capable of participating in the UUF activity, and all other (non-participating) stations should be terminated. There are two exceptions for stations that are not capable of participating in the UUF and are required to be retained in the protocol until concluded. They shall be handled using either of the two following procedures. First, the calling station shall direct all the addressed and included stations to stay linked for the duration of the UUF, to read and use anything that they are capable of during that time, and to resume acquisition and tracking of the ALE frame and protocol after the UUF ends. To accomplish this, and immediately before the CMD UUF, the sending station shall send the CMD STAY, which shall indicate the time period (T) for which the receiving stations shall wait for resumption of the frame and protocol. Second, the sending station shall use any standard CMD function to direct the non-participating stations to wait or return later, or do anything else appropriate and controllable through the standard orderwire functions.

    If a CMD UUF is included within an ALE frame, it shall only be within the message section. The UUF activity itself should be conducted completely outside of the frame and should not interfere with the protocols. If the UUF activity itself must be conducted within the message section, will occupy time on the channel, and is incompatible with the ALE system, that activity shall be conducted immediately after the CMD UUF and it shall be for a limited amount of time (T). A CMD STAY shall precede the UUF instruction, as described herein, to indicate that time (T). The sending station shall resume the same previous redundant word phase when the frame and protocol resumes, to ensure synchronization. The STAY function preserves maintenance of the frame and link. It instructs the stations to wait, because the amount of time occupied by the UUF activity or its signaling may conflict with functions such as the wait-for-activity timer (Twa). This may interfere with the protocols or maintenance of the link. In any case, the users of the UUF shall be responsible for noninterference with other stations and users, and also for controlling their own stations and link management functions to avoid these conflicts.

    The UUF shall be constructed as follows and as shown in table A-XXX. The UUF word shall use the CMD (110) preamble in bits P3 through P1 (W1 through W3). The character in the first position shall be the pipe "¦" or vertical bar "|" (1111100) in bits C1-7 through C1-1 (W4 through W10), which shall identify the "unique" function. The user or manufacturer-specific UI shall be a 14-bit (or two-character, 7-bit ASCII) code using bits UI-14 through UI-1 (W11 through W24). All unassigned UI codes shall be reserved and shall not be used until assigned for a specific use.

    TABLE A-XXX. User unique functions structure.
    User Unique

    Function Bits


    Word Bits
    CMD Preamble MSB

    LSB

    P3=1

    P2=1

    P1=0

    MSBW1

    W2

    W3

    First Character ¦ MSB




    LSB

    C1 (bit-7) =1

    C1 (bit-6)=1

    C1 (bit-5) =1

    C1 (bit-4) =1

    C1 (bit-3) =1

    C1 (bit-2) =0

    C1 (bit-1) =0

    W4

    W5

    W6

    W7

    W8

    W9

    W10

    First UI Character MSB




    LSB

    UI-1-7

    UI-1-6

    UI-1-5

    UI-1-4

    UI-1-3

    UI-1-2

    UI-1-1

    W11

    W12

    W13

    W14

    W15

    W16

    W17

    Second UI Character MSB




    LSB

    UI-2-7

    UI-2-6

    UI-2-5

    UI-2-4

    UI-2-3

    UI-2-2

    UI-2-1







    LSB
    W18

    W19

    W20

    W21

    W22

    W23

    W24

    NOTES:
    1. CMD user unique functions first character is " ¦ " (1111100) for "unique."
    2. Unique index (UI) characters UI-1 and UI-2 from central registry and assignment.

    A.5.7 ALE message protocols.

    A.5.7.1 Overview.

    Three message protocols are available for carrying user data using the ALE waveform and signal structure. The characteristics of these three protocols are summarized in the table A-XXXI. All ALE controllers complying with this appendix shall implement the AMD protocol.

    TABLE A-XXXI. ALE message protocols.
    ProtocolMandatory Character Set Peak Throughput ARQ
    AMDY Expanded 6455 b/s N
    DTMN unrestricted61 b/s Opt
    DBMN unrestricted187 b/s Opt

    A.5.7.2 AMD mode (mandatory).

    The operators and controllers shall be able to send and receive simple ASCII text messages using only the existing station equipment.

    A.5.7.2.1 Expanded 64-channel subset.

    The expanded 64 ASCII subset shall include all capital alphabetics (A-Z), all digits (0-9), the utility symbols "@" and "?," plus 26 other commonly used symbols. See figure A-46. The expanded 64 subset shall be used for all basic orderwire message functions, plus special functions as may be standardized. For orderwire message use, the subset members shall be enclosed within a sequence of DATA (and REP) words and shall be preceded by an associated CMD (such as DTM). The CMD designates the usage of the information that follows, and shall also be preceded by a valid and appropriate calling cycle using the Basic 38 ASCII subset addressing. Digital discrimination of the expanded 64 ASCII subset may be accomplished by examination of the two MSBs (b7 and b6), as all of the members within the "01" and "10" MSBs are acceptable. No parity bits are transmitted because the integrity of the information is protected by the basic ALE FEC and redundancy and may be ensured by optional use of the CMD CRC as described in A.5.6.1. The station shall have the capability to both send and receive AMD messages from and to both the operator and the controller. The station shall also have the capability to display any received AMD messages directly to the operator and controller upon arrival, and to alert them. The operator and controller shall have the capability to disable the display and the alarm when their functions would be operationally inappropriate.



    FIGURE A-46. Expanded 64 ASCII subset (shown unshaded).

    A.5.7.2.2 AMD protocol.

    When an ASCII short orderwire AMD type function is required, the following CMD AMD protocol shall be used, unless another protocol in this standard is substituted. An AMD message shall be constructed in the standard word format, as described herein, and the AMD message shall be inserted in the message section of the frame. The receiving station shall be capable of receiving an AMD message contained in any ALE frame, including calls, responses, and acknowledgments. Within the AMD structure, the first word shall be a CMD AMD word, which shall contain the first three characters of the message. It shall be followed by a sequence of alternating DATA and REP words that shall contain the remainder of the message. The CMD, DATA, and REP words shall all contain only characters from the expanded ASCII 64 subset, which shall identify them as an AMD transmission. Each separate AMD message shall be kept intact and shall only be sent in a single frame, and in the exact sequence of the message itself. If one or two additional characters are required to fill the triplet in the last word sent, the position(s) shall be "stuffed" with the "space" character (0100000) automatically by the controller, without operator action. The end of the AMD message shall be indicated by the start of the frame conclusion, or by the receipt of another CMD. Multiple AMD messages may be sent within a frame, but they each shall start with their own CMD AMD with the first three characters.

    A.5.7.2.3 Maximum AMD message size.

    Receipt of the CMD AMD word shall warn the receiving station that an AMD message is arriving and shall instruct it to alert the operator and controller and display the message, unless they disable these outputs. The station shall have the capability to distinguish among, and separately display, multiple separate AMD messages that were in one or several transmissions.

    The AMD word format shall consist of a CMD (110) in bits P3 through P1 (W1 through W3), followed by the three standard character fields C1, C2, and C3. In each character field, each character shall have its most significant bits (MSBs) bit 7 and bit 6 (C1-7 and C1-6, C2-7 and C2-6, and C3-7 and C3-6) set to the values of "01" or "10" (that is, all three characters are members of the expanded ASCII 64 subset). The rest of the AMD message shall be constructed identically, except for the alternating use of the DATA and REP preambles.

    Any quantity of AMD words may be sent within the message section of the frame within the

    Tm max limitation of 30 words (90 characters). Tm max shall be expanded from 30 words, to a maximum of 59 words, with the inclusion of CMD words within the message section. The maximum AMD message shall remain 30 words, exclusive of additional CMD words included within the message section of the frame. The maximum number of CMD words within the message section shall be 30. The message characters within the AMD structure shall be displayed verbatim as received. If a detectable information loss or error occurs, the station shall warn of this by the substitution of a unique and distinct error indication, such as all display elements activated (like a "block"). The display shall have a capacity of at least 20 characters (DO: at least 40). The AMD message storage capacity, for recall of the most recently received message(s), shall be at least 90 characters plus sending station address. (DO: at least 400). By operator or controller direction, the display shall be capable of reviewing all messages in the AMD memory and shall also be capable of identifying the originating station's address. If words are received that have the proper AMD format but are within a portion of the message section under the control of another message protocol (such as DTM), the other protocol shall take precedence and the words shall be ignored by the station's AMD function.

    NOTE: If higher data integrity or reliability is required, the CMD DTM and DBM protocols should be used.

    A.5.7.3 DTM mode.

    The DTM ALE (orderwire) message protocol function enables stations to communicate (full ASCII or unformatted binary bits) messages to and from any selected station(s) for direct output to and input from associated data terminals or other date terminal equipment (DTE) devices through their standard data circuit-terminating equipment (DCE) ports. The DTM data transfer function is a standard speed mode (like AMD) with improved robustness, especially against weak signals and short noise bursts. When used over medium frequency (MF)/HF by the ALE system, DTM orderwire messages may be unilateral or bilateral, and broadcast or acknowledged. As the DTM data blocks are of moderate sizes, this special orderwire message function enables utilization of the inherent redundancy and FEC techniques to detect weak HF signals and tolerate short noise bursts.

    The DTM data blocks shall be fully buffered at each station and should appear transparent to the using DTEs or data terminals. As a DO, and under the direction of the operator or controller, the stations should have the capability of using the DTM data traffic mode (ASCII or binary bits) to control switching of the DTM data traffic to the appropriate DCE port or associated DTE equipment, such as to printers and terminals (if ASCII mode), or computers and cryptographic devices (if binary bits mode). As an operator or controller selected option, the received DTM message may also be presented on the operator display similar to the method for AMD in A.5.7.2.

    There are four CMD DTM modes: BASIC, EXTENDED, NULL, and ARQ. The DTM BASIC block ranges over a moderate size and contains a variable quantity of data, from zero to full as required, which is exactly measured to ensure integrity of the data during transfer. The DTM EXTENDED blocks are variable over a larger range of sizes, in integral multiples of the ALE basic word, and are filled with integral multiples of message data. The DTM NULL and ARQ modes are used for both link management, and error and flow control. The characteristics of the CMD DTM orderwire message functions are listed in table A-XXXII and are summarized below:

    CMD DTM Mode BASIC EXTENDED ARQ NULL
    Maximum Size, Bits651 73710
    Cyclic Redundancy Check16 Bits 16 Bits0
    Data Capacity, ASCII0-93 3-1053, by 30
    Data Capacity, Bits1-651 21-7371, by 210
    ALE Word Redundancy3 Fixed 3 Fixed0
    Data Transmission392 ms - 392 ms -0
    12.152 sec2.29 min

    TABLE A-XXXII. DTM characteristics.


    When an ASCII, or binary bit, digital data message function is required, the following CMD DTM orderwire structures and protocols shall be used as specified herein, unless another standardized protocol is substituted. The DTM structure shall be inserted within the message section of the standard ALE frame. A CMD DTM word shall be constructed in the standard
    24-bit format, using the CMD preamble (see table A-XXXIII). The message data to be transferred shall also be inserted in words, using the DATA and REP preambles. The words shall then be Golay FEC encoded and interleaved, and then shall be transmitted immediately following the CMD DTM word. A CMD CRC shall immediately follow the data block words, and it shall carry the error control CRC FCS.

    When the DTM structure transmission time exceeds the maximum limit for the message section (Tm max), the DTM protocol shall take precedence and shall extend the Tm limit to accommodate the DTM. The DTM mode preserves the required consistency of redundant word phase during the transmission. The message expansion due to the DTM is always a multiple of one Trw, as the basic ALE word structure is used. The transmission time of the DTM data block (DTM words x 392 ms) does not include the Trw for the preceding CMD DTM word or the following CMD CRC. Figure A-47 shows an example of a DTM message structure.



    FIGURE A-47. DTM structure example.

    The DTM protocol shall be as described herein. The CMD DTM BASIC and EXTENDED formats (herein referred to as DTM data blocks) shall be used to transfer messages and information among stations. The CMD DTM ARQ format shall be used to acknowledge other CMD DTM formats and for error and flow control, except for non-ARQ and one-way broadcasts. The CMD DTM NULL format shall be used to (a) interrupt ("break") the DTM and message flow, (b) to interrogate station to confirm DTM capability before initiation of the DTM message transfer protocols, and (c) to terminate the DTM protocols while remaining linked. When used in ALE handshakes and subsequent exchanges, the protocol frame terminations for all involved stations shall be TIS until all the DTM messages are successfully transferred, and all are acknowledged if ARQ error control is required. The only exceptions shall be when the protocol is a one-way broadcast or the station is forced to abandon the exchange by the operator or controller, in which cases the termination should be TWAS.

    Once a CMD DTM word of any type has been received by a called (addressed) or linked station, the station shall remain on channel for the entire specified DTM data block time (if any), unless forced to abandon the protocol by the operator or controller. The start of the DTM data block itself shall be exactly indicated by the end of the CMD DTM BASIC or EXTENDED word itself. The station shall attempt to read the entire DTM data block information in the DATA and REP words, and the following CMD CRC, plus the expected frame continuation, which shall contain a conclusion (possibly preceded by additional functions in the message section, as indicated by additional CMD words).

    With or without ARQ, identification of each DTM data block and its associated orderwire message (if segmented into sequential DTM data blocks) shall be achieved by use of the sequence and message control bits, KD1 and KD2, (as shown in table A-XXXIII), which shall alternate with each DTM transmission and message, respectively. The type of data contained within the data block (ASCII or binary bits) shall be indicated by KD3 as a data identification bit. Activation of the ARQ error control protocol shall use the ARQ control bit KD4. If no ARQ is required, such as in one-way broadcasts, multiple DTM data blocks may be sent in the same frame, but they shall be in proper sequential order if they are transferring a segmented message.

    When ARQ error or flow control is required, the CMD DTM ARQ shall identify the acknowledged DTM data block by the use of the sequence and message control bits KD1 and KD2, which shall be set to the same values as the immediately preceding and referenced DTM data block transmission. Control bit KD3 shall be used as the DTM flow control to pause or continue (or resume) the flow of the DTM data blocks. The ACK and request-for-repeat (NAK) functions shall use the ARQ control bit KD4. If no ARQ has been required by the sending station, but the receiving station needs to control the flow of the DTM data blocks, it shall use the DTM ARQ to request a pause in, and resumption of, the flow.

    TABLE A-XXXIII. DTM structure.
    DTM Bits Word Bits
    CMD

    preamble

    MSB

    LSB

    P3=1

    P2=1

    P1=0

    MSBW1

    W2

    W3

    First

    character

    "d"

    MSB




    LSB

    C1 (bit-7) = 1

    C1 (bit-6) = 1

    C1 (bit-5) = 0

    C1 (bit-4) = 0

    C1 (bit-3) = 1

    C1 (bit-2) = 0

    C1 (bit-1) = 0

    W4

    W5

    W6

    W7

    W8

    W9

    W10

    Control

    bits

    MSB

    LSB

    KD4

    KD3

    KD2

    KD1

    W11

    W12

    W13

    W14

    DTM

    data

    code

    bits

    MSB







    LSB

    DC10

    DC9

    DC8

    DC7

    DC6

    DC5

    DC4

    DC3

    DC2

    DC1










    LSB
    W15

    W16

    W17

    W18

    W19

    W20

    W21

    W22

    W23

    W24

    NOTES:
    1. CMD DTM and DTM ARQ first character is "d" for "data".
    2. With DTM transmission, control bit KD4 (W11) is set to "0" for no ACK request, and "1" for ACK request.
    3. If a DTM ARQ transmission, control bit KD4 (W11) is set to "0" for binary bits, and "1" for 7-bit ASCII characters.
    4. With DTM transmission, control bit KD3 (W12) is set to "0" for binary bits and "1" for 7-bit ASCII characters.
    5. If a DTM ARQ transmission, control bit KD3 (W12) is set to "0" for flow continue, and "1" for flow pause.
    6. With DTM transmissions, control bit KD2 (W13) is set (a) the same ("0" or "1") as the sequentially adjacent DTM(s) if the transmitted data field is to be reintegrated as part of a larger DTM, and (b) alternately different if independent from the prior adjacent DTM data field(s).
    7. If a DTM ARQ transmission, control bit KD2 (W13) is set the same as the referenced DTM transmission.
    8. With DTM transmission, control bit KD1 (W14) is set alternately to "0" and "1" in any sequence of DTMs, as a sequence control.
    9. If a DTM ARQ transmission, control bit KD1 (W14) is set the same as the referenced DTM transmission.
    10. Data Code (DC) bits are from table A-XXXII.

    When data transfer ARQ error and flow control is required, the DTM data blocks shall be sent individually, in sequence, and each DTM data block shall be acknowledged before the next DTM data block is sent. Therefore, with ARQ there shall be only one DTM data block transmission in each ALE frame. If the transmitted DTM data block causes a NAK in the returned DTM ARQ, as described below, or if ACK or DTM ARQ is detected in the returned frame, or if no ALE frame is detected at all, the sending station shall resend an exact duplicate of the unacknowledged DTM data block. It shall send and continue to resend duplicates (which should be up to at least seven) one at a time and with appropriate pauses for responses, until the involved DTM data block is specifically acknowledged by a correct DTM ARQ. Only then shall the next DTM data block in the sequence be sent. If the sending station is frequently or totally unable to detect ALE frame or DTM ARQ responses, it should abort the DTM transfer protocol, terminate the link, and relink and reinitiate the DTM protocol on a better channel, under operator or controller direction.

    Before initiation of the DTM data transfer protocols, the sending stations should confirm the existence of the DTM capability in the intended receiving stations, if not already known. When a DTM interrogation function is required, the following protocol shall be used. Within any standard protocol frame (using TIS), the sending station shall transmit a CMD DTM NULL, with ARQ required, to the intended station(s). These receiving stations shall respond with the appropriate standard frame and protocol, with the following variations. They shall include a CMD DTM ARQ if they are DTM capable, and they shall omit it if they are not DTM capable. The sending station shall examine the ALE and DTM ARQ responses for existence, correctness, and the status of the DTM KD control bits, as described herein. The transmitted CMD DTM NULL shall have its control bits set as follows: KD1 and KD2 set opposite of any subsequent and sequential CMD DTM BASIC or EXTENDED data blocks, which will be transmitted next; KD3 set to indicate the intended type of traffic, and KD4 set to require ARQ. The returned CMD DTM ARQ shall have its control bits set as follows: KD1 and KD2 set to match the interrogating DTM NULL; KD3 set to indicate if the station is ready for DTM data exchanges, or if a pause is requested; and KD4 set to ACK if the station is ready to accept DTM data transmissions with the specified traffic type, and NAK if it cannot or will not participate, or it failed to read the DTM NULL.

    The sending (interrogating) station shall handle any and all stations that return a NAK, or do not return a DTM ARQ at all, or do not respond at all, in any combination of the following three ways, and for any combination of these stations. The specific actions and stations shall be selected by the operator or controller. The sending station shall: (a) terminate the link with them, using an appropriate and specific call and the TWAS terminator; or (b) direct them to remain and stay linked during the transmissions, using the CMD STAY protocol in each frame immediately before each CMD DTM word and data block sent; or (c) redirect them to do anything else that is controllable using the CMD functions described within this standard.

    Each received DTM data block shall be examined using the CRC data integrity test included within the mandatory associated CMD CRC that immediately follows the DTM data block structure. If the data block passes the CRC test, the data shall be passed through to the appropriate DCE port (or normal output as directed by the operator or controller). If the data block is part of a larger message segmented before DTM transfer, it shall be recombined before output. If any DTM data blocks are received and do not pass the CRC data integrity test, any detectable but uncorrectable errors or areas likely to contain errors and should be tagged for further analysis, error control, or inspection by the operator or controller.

    If ARQ is required, the received but unacceptable data block shall be temporarily stored, and a DTM ARQ NAK shall be returned to sender, who shall retransmit an exact duplicate DTM data block. Upon receipt of the duplicate, the receiving station shall again test the CRC. If the CRC is successful, the data block shall be passed through as described before, the previously unacceptable data block should be deleted, and a DTM ARQ ACK shall be returned. If the CRC fails again, both the duplicate and the previously stored data blocks shall be used to correct, as possible, errors and to create an "improved" data block. See figure A-48 for an example of data block reconstruction. The "improved" data block shall then be CRC tested. If the CRC is successful, the "improved" data block is passed through, the previously unacceptable data blocks should be deleted, and a DTM ARQ ACK shall be returned. If the CRC test fails, the "improved" data block shall be stored and a DTM ARQ NAK shall be returned. This process shall be repeated until: (a) a received duplicate, or an "improved" data block passes the CRC test (the data block is passed through, and a DTM ARQ ACK is returned); (b) the maximum number of duplicates (such as seven or more) have been sent without success (with actions by the sender as described above); or (c) the operators or controllers terminate or redirect the DTM protocol.


    FIGURE A-48. Data test message reconstruction (overlay).

    During reception of ALE frames and DTM data blocks, it is expected that fades, interferences, and collisions will occur. The receiving station shall have the capability to maintain synchronization with the frame and the DTM data block transmission, once initiated. It shall also have the capability to read and process any colliding and significantly stronger (that is, readable) ALE signals without confusing them with the DTM signal (basic ALE reception in parallel, and always listening). Therefore, useful information that may be derived from readable collisions of ALE signals should not be arbitrarily rejected or wasted. The DTM structures, especially the DTM EXTENDED, can tolerate weak signals, short fades, and short noise bursts. For these cases and for collisions, the DTM protocol can detect DTM words that have been damaged and "tag" them for error correction or repeats. The DTM constructions are described herein. Within the DTM data block structure, the CMD DTM word shall be placed ahead of the DTM data block itself. The DTM word shall alert the receiving station that a DTM data block is arriving, how long it is, what type of traffic it contains, what its message and block sequence is, and if ARQ is required. It shall also indicate the exact start of the data block (the end of the CMD DTM word), and shall initiate the reception, tracking, decoding, reading, and checking of the message data contained within the data block, which itself is within the DATA and REP words. The message data itself shall be either one of two types, binary bits or ASCII.

    The ASCII characters (typically used for text) shall be the standard 7-bit length, and the start, stop, and parity bits shall be removed at the sending (and restored at the receiving) station. The binary bits (typically used for other character formats, computer files, and cryptographic devices) may have any (or no) pattern or format, and they shall be transferred transparently (that is, exactly as they were input to the sending station) with the same length and without modification.

    The size of the DTM BASIC or EXTENDED data block shall be the smallest multiple of DATA and REP words that will accommodate the quantity of the ASCII or binary bits message data to be transferred in the DTM data block. If the message data to be transferred does not exactly fit the unencoded data field of the DTM block size selected, the available empty positions shall be "stuffed" with ASCII "DEL" (1111111) characters or all "1" bits. The combined message and "stuff" data in the uncoded DTM data field shall then be checked by the CRC for error control in the DTM protocol. The resulting 16-bit CRC word shall always be inserted into the CMD CRC word that immediately follows the DTM data block words themselves. All the bits in the data field shall then be inserted into standard DATA and REP words on a 21-bit or three-character basis and Golay FEC encoded, interleaved, and tripled for redundancy. Immediately after the CMD DTM word, the DTM DATA and REP words shall follow standard word format, and the CMD CRC shall be at the end.

    The DTM BASIC data block has a relatively compact range of sizes from 0 to 31 words and shall be used to transfer any quantity of message data between zero and the maximum limits for the DTM BASIC structure, which is up to 651 bits or 93 ASCII characters. It is capable of counting the exact quantity of message data it contains, on a bit-by-bit basis. It should be used as a single DTM for any message data within this range. It shall also be used to transfer any message data in this size range that is an "overflow" from the larger size (and increments) DTM EXTENDED data blocks, which shall immediately precede the DTM BASIC in the DTM sequence of sending.

    The DTM EXTENDED data blocks are also variable in size in increments of single ALE words up to 351. They should be used as a single, large DTM to maximize the advantages of DTM throughput. The size of the data block should be selected to provide the largest data field size that can be totally filled by the message data to be transferred. Any "overflow" shall be in a message data segment sent within an immediately following and appropriately sized DTM EXTENDED or BASIC data block. Under operator or controller direction, multiple DTM EXTENDED data blocks, with smaller than the maximum appropriate ID sizes, should be selected if they will optimize DTM data transfer throughput and reliability. However, these multiple data blocks will require that the message data be divided into multiple segments at the sending station, that they be sent only in the exact order of the segments in the message, and that the receiving stations recombine the segments into a complete received message. When binary bits are being transferred, the EXTENDED data field shall be filled exactly to the last bit. When ASCII characters are being transferred, there are no stuff bits as the 7-bit characters fit the ALE word 21-bit data field exactly.

    If stations are exchanging DTM data blocks and DTM ARQs, they may combine both functions in the same frames, and they shall discriminate based on the direction of transmission and the sending and destination addressing. If ARQ is required in a given direction, only one DTM data block shall be allowed within any frame in that direction, and only one DTM ARQ shall be allowed in each frame in the return direction. If no ARQ is required in a given direction, multiple DTM data blocks may be included in frames in that direction, and multiple DTM ARQ's may be included in the return direction.

    As always throughout the DTM protocol, any sequence of DTM data blocks to be transferred shall have the KD1 sequence control bits alternating with the preceding and following DTM data blocks (except duplicates for ARQ, which shall be exactly the same as the originally transmitted DTM data block).

    Also, all multiple DTM data blocks transferring multiple segments of a larger data message shall all have their KD2 message control bits set to the same value, and opposite of the preceding and following messages. If a sequence of multiple but unrelated DTM data blocks are sent (such as several independent and short messages within several DTM BASIC data blocks), they may be sent in any sequence. However, the KD1 or KD2 sequence and message control bits shall alternate with those in the adjacent DTM data blocks.

    The CMD DTM words shall be constructed as shown in table A-XXXIII. The preamble shall be CMD (110) in bits P3 through P1 (W1 through W3). The first character shall be "d" (1100100) in bits C1-7 through C1-1) (W4 through W10), which shall identify the DTM "data" function.

    For DTM BASIC, EXTENDED, and NULL, when the "ARQ" control bit KD4 (W11) is set to "0," no correct data receipt acknowledgment is required; and when set to "1," it is required. For DTM ARQ, "ARQ" control bit KD4 is set to "0" to indicate acknowledgment or correct data block receipt (ACK); and when set to "1," it indicates a failure to receive the data and is therefore a request-for-repeat (NAK). For DTM ARQ responding to a DTM NULL interrogation, KD4 "0" indicates non-participation in the DTM protocol or traffic type, and KD4 "1" indicates affirmative participation in both the DTM protocol and traffic type.

    For DTM BASIC, EXTENDED, and NULL, when the "data type" control bit KD3 (W12) is set to "0," the message data contained within the DTM data block shall be binary bits with no required format or pattern; and when KD3 is set to "1" the message data is 7-bit ASCII characters. For DTM ARQ, "flow" control bit KD3 is set to indicate that the DTM transfer flow should continue, or resume; and when KD3 is set to "1" it indicates that the sending station should pause (until another and identical DTM ARQ is returned, except that KD3 shall be "0").

    For DTM BASIC, EXTENDED, and NULL, when the "message" control bit KD2 (W13) is set to the same value as the KD2 in any sequentially adjacent DTM data block, the message data contained within those adjacent blocks (after individual error control) shall be recombined with the message data within the present DTM data block segment-by-segment to reconstitute the original whole message, and when KD2 is set opposite to any sequentially adjacent DTM data blocks, those data blocks contain separate message data and shall not be combined. For DTM ARQ, "message" control bit KD2 shall be set to match the referenced DTM data block KD2 value to provide message confirmation.

    For DTM BASIC, EXTENDED, and NULL, the "sequence" control bit KD1 (W14) shall be set opposite to the KD1 value in the sequentially adjacent DTM BASIC, EXTENDED, or NULLs to be sent (the KD1 values therefore alternate, regardless of their message dependencies). When KD1 is set to the same value as any sequentially adjacent DTM sent, it indicates that it is a duplicate (which shall be exactly the same). For DTM ARQ, "sequence" control bit KD1 shall be set to match the referenced DTM data block or NULL KD1 value to provide sequence confirmation.

    When used for the DTM protocols, the ten DTM data code (DC) bits DC10 through DC1 (W15 through W24) shall indicate the DTM mode (BASIC, EXTENDED, ARQ, or NULL). They shall also indicate the size of the message data and the length of the data block. The DTM NULL DC value shall be "0" (0000000000), and it shall designate the single CMD DTM NULL word. The DTM EXTENDED DC values shall range from "1" (0000000001) to "351" (0101011111), and they designate the CMD DTM EXTENDED word and the data block multiple of DATA and REP words that define the variable data block sizes. The EXTENDED sizes shall range from 1 to 351 words, with a range of 21 to 7371 binary bits, in increments of 21; or three to 1053 ASCII characters, in increments of three. The DTM BASIC DC values shall range from "353" (0101100001) to "1023" (1111111111), and they shall designate the CMD DTM BASIC word and the exact size of the message data in compact and variable size data blocks, with up to 651 binary bits or 93 ASCII characters. The DTM ARQ DC value shall be "352" (0101100000), and it shall designate the single CMD DTM ARQ word. The DC values "384" (0110000000) and all higher multiples of "32m" (m x 100000) shall be reserved until standardized. See table A-XXXII for DC values and DTM block sizes and other characteristics.

    A.5.7.4 DBM mode.

    The DBM ALE (orderwire) message protocol function enables ALE stations to communicate either full ASCII, or unformatted binary bit messages to and from any selected ALE station(s) for direct output to and input from associated data terminal or other DTE devices through their standard DCE ports. This DBM data transfer function is a high-speed mode (relative to DTM and AMD) with improved robustness, especially against long fades and noise bursts. When used over MF/HF by the ALE system, DBM orderwire messages may be unilateral or bilateral, and broadcast or acknowledged. As the DBM data blocks can be very large, this special orderwire message function enables exploitation of deep interleaving and FEC techniques to penetrate HF-channel long fades and large noise bursts.

    The DBM data blocks shall be fully buffered at each station and should appear transparent to the using DTEs or data terminals. As a design objective and under the direction of the operator or controller, the stations should have the capability of using the DBM data traffic mode (ASCII or binary bits) to control switching of the DBM data traffic to the appropriate DCE port or associated DTE equipment, such as to printers and terminals (if ASCII mode) or computers and cryptographic devices (if binary bits mode). As an operator or controller-selected option, the received DBM message may also be presented on the operator display, similar to the method for AMD in table A.5.7.2.

    There are four CMD DBM modes: BASIC, EXTENDED, NULL, and ARQ. The DBM BASIC block is a fixed size and contains a variable quantity of data, from zero to full as required, which is exactly measured to ensure integrity of the data during transfer. The DBM EXTENDED blocks are variable in size in integral multiples of the BASIC block, and are filled with integral multiples of message data. The DBM NULL and ARQ modes are used for both link management, and error and flow control. The characteristics of the CMD DBM orderwire message functions are listed in table A-XXXIV, and they are summarized below:
    CMD DBM ModeBASIC EXTENDEDARQ NULL
    Maximum Size, Bits588 2628360
    CRC16 Bits16 Bits 0
    Data Capacity, ASCII0-81 81-37377, by 840
    Data Capacity, Bits0-572 572-261644, by 5880
    ALE Word Redundancy49 Fixed 49-21805, by 490
    Data Transmission3.136 Sec 3.136 sec - 23.26 min, 0
    by 3.136 sec increments

    TABLE A-XXXIV. DBM characteristics.


    When an ASCII, or binary bit, digital data message function is required, the following CMD DBM orderwire structures and protocols shall be used as specified herein, unless another standardized protocol is substituted. The DBM structure shall be inserted within the message section of the standard frame. A CMD DBM word shall be constructed in the standard format. The data to be transferred shall be Golay FEC encoded, interleaved (for error spreading during decoding), and transmitted immediately following the CMD DBM word.

    When the DBM structure transmission time exceeds the maximum for the message section

    (Tm max), the DBM protocol shall take precedence and shall extend the Tm limit to accommodate the DBM. The DBM mode preserves the required consistency of redundant word phase during the transmission. The message expansion due to the DBM is always a multiple of 8 Trw, as the interleaver depth is always a multiple of 49. The transmission time of the DBM data block (Tdbm) itself is equal to (interleaver depth x 64ms), not including the Trw for the preceding CMD DBM word. Figure A-49 shows an example of an exchange using the DBM orderwire to transfer and acknowledge messages. Figure A-50 shows an example of a DBM data interleaver, and figure A-51 shows the transmitted DBM bit-stream sequence.



    FIGURE A-49. Data test message structure and ARQ example.


    FIGURE A-50. DBM interleaver and deinterleaver.


    FIGURE A-51. DBM example.

    The DBM protocol shall be as described herein. The CMD DBM BASIC and EXTENDED formats (herein referred to as DBM data blocks) shall be used to transfer messages in information among ALE stations. The CMD DBM ARQ format shall be used to acknowledge other CMD DBM formats and for error and flow control, except for non-ARQ and one-way broadcasts. The CMD DBM NULL format shall be used to: (a) interrupt ("break") the DBM and message flow; (b) to interrogate stations to confirm DBM capability before initiation of the DBM message transfer protocols; and (c) to terminate the DBM protocols while remaining linked. When used in handshakes and subsequent exchanges, the protocol frame terminations for all involved stations shall be TIS until all the DBM messages are successfully transferred, and all are acknowledged if ARQ error control is required. The only exceptions shall be when the protocol is a one-way broadcast or the station is forced to abandon the exchange by the operator or controller, in which cases the termination should be TWAS.

    Once a CMD DBM word of any type has been received by a called (addressed) or linked station, the station shall remain on channel for the entire specified DBM data block time (if any), unless forced to abandon the protocol by the operator or controller. The start of the DBM data block itself shall be exactly indicated by the end of the CMD DBM BASIC or EXTENDED word itself. The station shall attempt to read the entire DBM data block information, plus the expected frame continuation, which shall contain a conclusion (possibly preceded by additional functions in the message section, as indicated by additional CMD words).

    With or without ARQ, identification of each DBM data block and its associated orderwire message (if segmented into sequential DBM data blocks) shall be achieved by use of the sequence and message control bits, KB1 and KB2, (see table A-XXXV) which shall alternate with each DBM transmission and message, respectively. The type of data contained within the data block (ASCII or binary bits) shall be indicated by KB3 as a data identification bit. Activation of the ARQ error-control protocol shall use the ARQ control bit KB4. If no ARQ is required, such as in one-way broadcasts, multiple DBM data blocks may be sent in the same frame, but they shall be in proper sequence if they are transferring a segmented message.

    TABLE A-XXXV. DBM structures.
    DBM Bits Word Bits
    CMD

    preamble

    MSB

    LSB

    P3 = 1

    P2 = 1

    P1 = 0

    MSB W3

    W1

    W2

    First

    character

    "b"

    MSB




    LSB

    C1 (bit-7) = 1

    C1 (bit-6) = 1

    C1 (bit-5) = 0

    C1 (bit-4) = 0

    C1 (bit-3) = 0

    C1 (bit-2) = 1

    C1 (bit-1) = 0

    W4

    W5

    W6

    W7

    W8

    W9

    W10

    Control

    bits

    MSB

    LSB

    KB4

    KB3

    KB2

    KB1

    W11

    W12

    W13

    W14

    DTM

    data

    code

    bits

    MSB







    LSB

    BC10

    BC9

    BC8

    BC7

    BC6

    BC5

    BC4

    BC3

    BC2

    BC1










    LSB
    W15

    W16

    W17

    W18

    W19

    W20

    W21

    W22

    W23

    W24


    NOTES:
    1. CMD DBM and DBM ARQ first character is "b" for "block."
    2. With DBM transmission, control bit KB4 (W11) is set to "0" for no ACK request, and "1" for ACK request.
    3. If a DBM ARQ transmission, control bit KB4 (W11) is set to "0" for ACK, and "1" for NAK.
    4. With DBM transmissions, control bit KB3 (W12) is set to "0" for binary bits and "1" for 7-bit ASCII characters.
    5. If a DBM ARQ transmission, control bit KB3 (W12) is set to "0" for flow continue, and "1" for flow pause.
    6. With DBM transmissions, control bit KB2 (W13) is set: (a) the same ("0" or "1") as the sequentially adjacent DBM(s) if the transmitted data field is to be reintegrated as part of a larger DBM, and (b) alternately different if independent from the prior adjacent DBM data field(s).
    7. If a DBM ARQ transmission, control bit KB2 (W13) is set the same as the referenced DBM transmission.
    8. With DBM transmissions, control bit KB1 (W14) is set alternately to "0" and "1" in any sequence of DBMs as a sequence control.
    9. If a DBM ARQ transmission, control bit KB1 (W14) is set the same as the referenced DBM transmission.
    10. Block code (BC) bits are from table A-XXXIV.

    When ARQ error or flow control is required, the CMD DBM ARQ shall identify the acknowledged DBM data block by the use of the sequence and message control bits KB1 and KB2, which shall be set to the same values as the immediately preceding and referenced DBM data block transmission. Control bit KB3 shall be used as the DBM flow control to pause or continue (or resume) the flow of the DBM data blocks. The ACK and NAK functions shall use the ARQ control bit KB4. If no ARQ has been required by the sending station, but the receiving station needs to control the flow of the DBM data blocks, it shall use the DBM ARQ to request a pause in, and resumption of, the flow.

    When data transfer ARQ error and flow control is required, the DBM data blocks shall be sent individually and in sequence. Each DBM data block shall be individually acknowledged before the next DBM data block is sent. Therefore, with ARQ there shall be only one DBM data block transmission in each frame. If the transmitted DBM data block causes a NAK in the returned DBM ARQ, as described below, or if no ACK or DBM ARQ is detected in the returned frame, or if no frame is detected at all, the sending station shall resend an exact duplicate of the unacknowledged DBM data block. It shall continue to resend duplicates (which should be at least seven), one at a time and with appropriate pauses for responses, until the involved DBM data block is specifically acknowledged by a correct DBM ARQ. Only then shall the next DBM data block in the sequence be sent. If the sending station is frequently or totally unable to detect frame or DBM ARQ responses, it should abort the DBM transfer protocol, terminate the link and relink and reinitiate the DBM protocol on a better channel (under operator or controller direction).

    Before initiation of the DBM data transfer protocols, the sending stations should confirm the existence of the DBM capability in the intended receiving stations, if not already known. When a DBM interrogation function is required, the following protocol shall be used. Within any standard protocol frame (using TIS), the sending station shall transmit a CMD DBM NULL, with ARQ required, to the intended station(s). These receiving stations shall respond with the appropriate standard frame and protocol, with the following variations. They shall include a CMD DBM ARQ if they are DBM capable, and they shall omit it if they are not DBM capable. The sending station shall examine the ALE and DBM ARQ responses for existence, correctness, and the status of the DBM KB control bits, as described herein. The transmitted CMD DBM NULL shall have its control bits set as follows: KB1 and KB2 set opposite of any subsequent and sequential CMD DBM BASIC or EXTENDED data blocks which will be transmitted next; KB3 set to indicate the intended type of traffic; and KB4 set to require ARQ. The returned CMD DBM ARQ shall have its control bits set as follows: KB1 and KB2 set to match the interrogating DBM NULL; KB3 set to indicate if the station is ready for DBM data exchanges, or if a pause is requested; and KB4 set to ACK if the station is ready to accept DBM data transmissions with the specified traffic type, and NAK if it cannot or will not participate, or if it failed to read the DBM NULL.

    The sending (interrogating) station shall handle any stations which return a NAK, or do not return a DBM ARQ, or do not respond, in any combination of the following, and for any combination of these stations. The specific actions and stations shall be selected by the operator or controller. The sending station shall: (a) terminate the link with these stations, using an appropriate and specific call and the TWAS terminator; (b) direct the stations to remain and stay linked during the transmissions, using the CMD STAY protocol in each frame immediately before each CMD DBM word and data block sent; or (c) redirect them to do anything else which is controllable using the CMD functions described within this standard.

    Each received DBM data block shall be examined using the CRC data integrity test which is embedded within the DBM structure and protocol. If the data block passes the CRC test, the data shall be passed through to the appropriate DCE port (or normal output as directed by the operator or controller). If the data block is part of a larger message which was segmented before DBM transfer, it shall be recombined before output. If any DBM data blocks are received and do not pass the CRC data integrity test, any detectable but uncorrectable errors; or areas likely to contain errors, should be tagged for further analysis, error control, or inspection by the operator or controller.

    If ARQ is required, the received but unacceptable data block shall be temporarily stored, and a DBM ARQ NAK shall be returned to the sender, who shall retransmit an exact duplicate DBM data block. Upon receipt of the duplicate, the receiving station shall again test the CRC. If the CRC is successful, the data block shall be passed through as described before, the previously unacceptable data block should be deleted, and a DBM ARQ ACK shall be returned. If the CRC fails again, both the duplicate and the previously stored data blocks shall be used to correct, as possible, errors and to create an "improved" data block. See figure A-48 for an example of data block reconstruction. The "improved" data block shall then be CRC tested. If the CRC is successful, the "improved" data block is passed through, the previously unacceptable data blocks should be deleted, and a DBM ARQ ACK shall be returned. If the CRC test fails, the "improved" data block shall also be stored and a DBM ARQ NAK shall be returned. This process shall be repeated until: (a) a received duplicate, or an "improved" data block passes the CRC test (and the data block is passed through, and a DBM ARQ ACK is returned); (b) the maximum number of duplicates (such as seven or more) have been sent without success (with actions by the sender as described above); or (c) the operators or controllers terminate or redirect the DBM protocol.

    During reception of frames and DBM data blocks, it is expected that fades, interferences, and collisions will occur. The receiving station shall have the capability to maintain synchronization with the frame and the DBM data block transmission, once initiated. It shall also have the capability to read and process any colliding and significantly stronger (that is, readable) ALE signals without confusing them with the DBM signal (basic ALE reception in parallel, and always listening). The DBM structures, especially the DBM EXTENDED, can tolerate significant fades, noise bursts, and collisions. Therefore, useful information which may be derived from readable collisions of ALE signals should not be arbitrarily rejected or wasted.

    The DBM constructions shall be as described herein. Within the DBM data block structure, a CMD DBM word shall be placed ahead of the encoded and interleaved data block itself. The DBM word shall alert the receiving station that a DBM data block is arriving, how long it is, what type of traffic it contains, what its interleaver depth is, what its message and block sequence is, and if ARQ is required. It shall also indicate the exact start of the data block itself (the end of the CMD DBM word itself) and shall initiate the reception, tracking, deinterleaving, decoding, and checking of the data contained within the block. The message data itself shall be either one of two types, binary bits or ASCII. The ASCII characters (typically used for text) shall be the standard 7-bit length, and the start, stop, and parity bits shall be removed at the sending (and restored at the receiving) station. The binary bits (typically used for other character formats, computer files, and cryptographic devices) may have any (or no) pattern or format, and they shall be transferred transparently, that is, exactly as they were input to the sending station, with the same length and without modification. The value of the interleaver depth shall be the smallest (multiple of 49) which will accommodate the quantity of ASCII or binary bits message data to be transferred in the DBM data block. If the message data to be transferred does not exactly fit the uncoded data field of the DBM block size selected (except for the last 16 bits, which are reserved for the CRC), the available empty positions shall be "stuffed" with ASCII "DEL" characters or all "1" bits. The combined message and "stuff" data in the uncoded DBM data field shall then be checked by the CRC for error control in the DBM protocol. The resulting 16-bit CRC word shall always occupy the last 16 bits in the data field. All the bits in the field shall then be Golay FEC encoded, on a 12-bit basis, to produce rows of 24-bit code words, arranged from top to bottom in the interleaver matrix (or equivalent), as shown in figure A-50. The bits in the matrix are then read out by columns (of length equal to the interleaver depth) for transmission. Immediately after the CMD DBM word, the encoded and interleaved data blocks bits shall follow in bit format, three bits per symbol (tone).

    The DBM BASIC data block has a fixed size (interleaver depth 49) and shall be used to transfer any quantity of message data between zero and the maximum limits for the DBM BASIC structure, which is up to 572 bits or 81 ASCII characters. It is capable of counting the exact quantity of message data which it contains, on a bit-by-bit basis. It should be used as a single DBM for any message data within this range. It shall also be used to transfer any message data in this size range which is an "overflow" from the larger size (and increments) DBM EXTENDED data blocks (which shall immediately precede the DBM BASIC in the DBM sequence of sending).

    The DBM EXTENDED data blocks are variable in size, in increments of 49 times the interleaver depth. They should be used as a single, large DBM to maximize the advantages of DBM deep interleaving, FEC techniques, and higher speed (than DTM or AMD) transfer of data. The interleaver depth of the EXTENDED data block should be selected to provide the largest data field size which can be totally filled by the message data to be transferred. Any "overflow" shall be in a message data segment sent within an immediately following DBM EXTENDED or BASIC data block. Under operator or controller direction, multiple DBM EXTENDED data blocks, with smaller than the maximum appropriate interleaver depth sizes, should be selected if they will optimize DBM data transfer throughput and reliability. However, these multiple data blocks will require that the message data be divided into multiple segments at the sending station and sent only in the exact order of the segments in the message. The receiving stations must recombine the segments into a complete received message. When binary bits are being transferred, the EXTENDED data field shall be filled exactly to the last bit. When ASCII characters are being transferred, the EXTENDED data field may have 0 to 6 "stuff" bits inserted. Individual ASCII characters shall not be split between DBM data blocks and the receiving station shall read the decoded data field on a 7-bit basis, and it shall discard any remaining "stuff" bits (modulo-7 remainder).

    If stations are exchanging DBM data blocks and DBM ARQs, they may combine both functions in the same frames. They shall discriminate based on the direction of transmission and the sending and destination addressing. If ARQ is required in a given direction, only one DBM data block shall be allowed within any frame in that direction, and only one DBM ARQ shall be allowed in each frame in the return direction. If no ARQ is required in a given direction, multiple DBM data blocks may be included in frames in that direction, and multiple DBM ARQs may be included in the return direction.

    As always throughout the DBM protocol, any sequence of DBM data blocks to be transferred shall have their KB1 sequence control bits alternating with the preceding and following DBM data blocks (except duplicates for ARQ, which shall be exactly the same as their originally transmitted DBM data block). Also, all multiple DBM data blocks transferring multiple segments of a large data message shall all have their KB2 message control bits set to the same value, and opposite of the preceding and following messages. If a sequence of multiple but unrelated DBM data blocks are sent (such as several independent and short messages within several DBM BASIC data blocks), they may be sent in any sequence. However, when sent, the associated KB1 and KB2 sequence and message control bits shall alternate with those in the adjacent DBM data blocks.

    The CMD DBM words shall be constructed as shown in table A-XXXV. The preamble shall be CMD (110) in bits P3 through P1 (W1 through W3). The first character shall be "b" (1100010) in bits C1-7 through C1-1 (W4 through W10), which shall identify the DBM "block" function.

    For DBM BASIC, EXTENDED, and NULL, when the ARQ control bit KB4 (W11) is set to "0," no correct data receipt acknowledgment is required; and when set to "1," it is required. For DBM ARQ, ARQ control bit KB4 is set to "0" to indicate acknowledgment or correct data block receipt (ACK); and when set to "1," it indicates a failure to receive the data and is therefore a request-for-repeat (NAK). For DBM ARQ responding to a DBM NULL interrogation, KB4 "0" indicates non-participation in the DBM protocol or traffic type, and KB4 "1" indicates affirmative participation in both the DBM protocol and traffic type.

    For DBM BASIC, EXTENDED, and NULL, when the data type control bit KB3 (W12) is set to "0," the message data contained within the DBM data block shall be binary bits with no required format or pattern; and when KB3 is set to "1" the message data is 7-bit ASCII characters. For DBM ARQ, flow control bit KB3 is set to "0" to indicate that the DBM transfer flow should continue or resume; and when KB3 is set to "1" it indicates that the sending station should pause (until another and identical DBM ARQ is returned, except that KB3 shall be "0").

    For DBM BASIC, EXTENDED, and NULL, when the "message" control bit KB2 (W13) is set to the same value as the KB2 in any sequentially adjacent DBM data block, the message data contained within those adjacent blocks (after individual error control) shall be recombined with the message data within the present DBM data block to reconstitute (segment-by-segment) the original whole message; and when KB2 is set opposite to any sequentially adjacent DBM data blocks, those data blocks contain separate message data and shall not be combined. For DBM ARQ, "message" control bit KB2 shall be set to match the referenced DBM data block KB2 value to provide message confirmation.

    For DBM BASIC, EXTENDED, and NULL, the sequence control bit KB1 (W14) shall be set opposite to the KB1 value in the sequentially adjacent DBM BASIC, EXTENDED, or NULLs be sent (the KB1 values therefore alternate, regardless of their message dependencies). When KB1 is set the same as any sequentially adjacent DBM sent, it indicates a duplicate. For DBM ARQ, sequence control bit KB1 shall be set to match the referenced DBM data block or NULL KB1 value to provide sequence confirmation.

    When used for the DBM protocols, the ten DBM data code (BC) bits BC10 through BC1 (W15 through W24) shall indicate the DBM mode (BASIC, EXTENDED, ARQ, or NULL). They shall also indicate the size of the message data and the length of the data block. The DBM NULL BC value shall be "0" (0000000000), and it shall designate the single CMD DBM NULL word. The DBM EXTENDED BC values shall range from "1" (0000000001) to "445" (0110111101), and they shall designate the CMD DBM EXTENDED word and the data block multiple (of 49 INTERLEAVER DEPTH) which defines the variable data block sizes, in increments of 588 binary bits or 84 ASCII characters. The DBM BASIC BC values shall range from "448" (0111000000) to "1020" (1111111100), and they shall designate the CMD DBM BASIC word and the exact size of the message data in a fixed size (INTERLEAVER DEPTH = 49) data block, with up to 572 binary bits or 81 ASCII characters. The DBM ARQ BC value shall be "1021" (1111111101), and it shall designate the single CMD DBM ARQ word.

    NOTES:

    1. The values "446" (0110111110) and "447" (0110111111) are reserved.

    2. The values "1022" (1111111110) and "1023" (1111111111) are reserved until standardized (see table A-XXXIV).

    A.5.8 AQC (optional) (NT).

    AQC-ALE is designed to use shorter linking transmissions than those of baseline second generation ALE (2G ALE) described previously in this appendix. AQC-ALE uses an extended version of the 2G ALE signaling structure to assure backward compatibility to already fielded radios. Special features of AQC-ALE include the following: