MIL-STD-187-721 Interoperability And Performance Standard For Advanced Adaptive Hf RadioThe purpose of this document is to describe the technical parameters for adaptive high frequency HF radio that are more advanced than those described in MIL-STD-188-141. The advanced technology contained in this standard will guide the planning of military adaptive HF radio network technology into the 21st century. To fully understand and utilize this document, it is necessary to refer to portions of MIL-STD-188-141.

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MIL-STD-187-721D

5.11.1 Control frame CMDs for link maintenance.

Automatic link maintenance CMDs shall be embedded in HFDLP control frames in the Extended function bits. An ALM CMD shall be indicated by a User ID code of 3FFE in hexadecimal (11

1111 1111 1110 binary). ALM CMDs shall be embedded in the 50 Function Bits as shown on figure 24.

2 6 42

V C M D

Arguments

FIGURE 24. ALM CMD format in HFDLP control frame function bits.

The V bits shall indicate the version of the HFDLP ALM CMD set in use. The current version is

00. The CMD field shall contain one of the CMDs listed below. The Arguments field shall contain arguments to the CMDs as indicated in the appropriate CMD description paragraph below.

The CMDs defined are in table XX for version 0 of the HFDLP ALM protocol:

TABLE XX. HFDLP ALM commands.

CMD Code 000000	CMD Name No Op	Arguments (none)
000001	Preferred Channels	One or more 7-bit channel numbers
000010	Assign Frequency	Flags, channel number, frequency
000011	Change Frequency	Frequency
000100	Adjust Power	Flags, adjustment

all others (reserved until standardized)

Channel numbers in the HFDLP ALM protocol are 7 bits long. When used with second- generation ALE, the 7 bits shall be interpreted as a channel number with a valid range of 1 to 100. When used with third-generation ALE, the 7 bits shall be interpreted as follows: the two most- significant bits shall select a channel list, and the five least-significant bits shall select a channel within that list. When the channel list bits are 00, they shall be interpreted as selecting the current channel list; otherwise, they shall select channel list 1, 2 or 3 (see 4.12.1.2.2).