MIL-STD-188-110 Interoperability And Performance Standards For Data ModemsThis document establishes mandatory technical standards and design objectives \(DO\) that are necessary to ensure interoperability and to promote performance among data modulators-demodulators \(modems\) used in the voice frequency \(VF\) band of long-haul and tactical communications systems. This document also provides guidance to the designers of new data modems that incorporate characteristics not yet standardized by specifying the technical characteristics of data modems currently in the inventory. The purpose of this guidance is to ensure attainment of minimum acceptable performance and maximum interoperability between existing and future data modems with specified transmission channel conditions.

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MIL-STD-188-110C

5 DETAILED REQUIREMENTS........................................................................................................16

5.1

Frequency shift keying (FSK) modems for single-channel radio equipment............................16

5.1.1 Narrow-shift FSK modem. ........................................................................................................... 16

5.1.2 Wide-shift FSK modem................................................................................................................ 16

5.2

FSK data modems for voice frequency (VF) channel operation (withdrawn). .........................16

5.3

HF data modems. ..........................................................................................................................16

5.3.1 General requirements. ................................................................................................................... 16

5.3.1.1 Capability. ...........................................................................................................................17

5.3.1.2 Voice digitization................................................................................................................17

5.3.1.3 Optional modes. ..................................................................................................................17

5.3.1.4 Interface requirements. .......................................................................................................18

5.3.1.4.1 Line-side data characteristics.......................................................................................18

5.3.1.4.2 LAN interface (DO). ....................................................................................................18

5.3.1.4.3 Equipment side characteristics (informative). ............................................................18

5.3.1.4.4 Transmit override. ........................................................................................................18

5.3.1.4.5 Buffering in synchronous serial mode. .......................................................................18

5.3.1.5 Remote control interface. ...................................................................................................18

5.3.1.5.1 Electrical interface........................................................................................................18

5.3.1.5.2 Optional modem control driver. ..................................................................................18

5.3.2 Serial (single-tone) mode. ............................................................................................................. 18

5.3.2.1 General. ...............................................................................................................................18

5.3.2.2 Sequencing of time phases. ................................................................................................19

5.3.2.2.1 Synchronization (sync) preamble phase. ....................................................................21

5.3.2.2.2 Data phase.....................................................................................................................24

5.3.2.2.3 EOM phase. ..................................................................................................................25

5.3.2.2.4 FEC coder and interleaver flush phase........................................................................25

5.3.2.3 Functional descriptions. ......................................................................................................25

5.3.2.3.1 EOM sequence. ............................................................................................................25

5.3.2.3.2 Interleaver flush............................................................................................................25

5.3.2.3.3 FEC encoder. ................................................................................................................25

5.3.2.3.4 Interleave load. .............................................................................................................28

5.3.2.3.5 Interleave fetch. ............................................................................................................29

5.3.2.3.6 Modified-Gray decoder................................................................................................30

5.3.2.3.7 Symbol formation.........................................................................................................31

5.3.2.3.8 Scrambler......................................................................................................................36

5.3.2.3.9 PSK modulation. ..........................................................................................................37

5.3.2.4 Waveform summary. ..........................................................................................................38

5.3.2.5 Performance requirements..................................................................................................38

5.3.3 Frequency hopping mode (optional). ........................................................................................... 39

5.3.4 Robust serial tone mode for severely degraded HF links (optional). ......................................... 39

6 NOTES ................................................................................................................................................40

6.1

Intended use. .................................................................................................................................40

6.2

Issue of Department of Defense Index of Specifications and Standards (DODISS). ...............40

6.3

Subject term (key word) listing. ...................................................................................................40