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MIL-STD-187_721.026566.pdf
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MlL-STD-l87-721
18 FEBRUARY 1993
MILITARY STANDARD
PLANNING AND GUIDANCE
STANDARD FOR AUTOMATED
CONTROL APPLIQUE FOR HF RADIO
AMSC fVA
DISTRIBUTIONSTA
TFMENT A.
Approvedforpublicrelease;distributionisunlimited.
AREA TCSS
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MIL-STD-187-721
FORENORD
1. This military standard is approved for use by all
Departments and Agencies of the Department of Defense.
2. Beneficial comments (recommendations, additions,
deletions) and any pertinent data which may be of use in
improving this document should be addressed to: HQ U.S. ArmY
Information Systems Engineering Command: ATTN : ASQB-OSE-TT,
Fort Huachuca, Arizona 85613-5300, by using the self-addressed
Standardization Document Improvement Proposal (DD Form 1426)
appearing at the end of this document or by letter.
3. Interoperability of DoD telecommunications systems, and of
DoD with non-DoD telecommunications systems, has been and will
continue to be a major consideration in the development and
adoption of standards for military use.
a.
Military standards in the 188 series (MIL-STD-188-XXX)
document telecommunications design parameters that are
based on empirical data, and must be used in all new or
major upgrades of inter-
and intra-DoD systems and
equipment to ensure interoperability.
b.
Military standards in the 187 series (MIL-STD-187-XXX)
document evolving telecommunications design parameters and
concepts that are subject to change and that have not been
adequately proven through the use of empirical test data.
MIL-STD-187-XXX standards should be used as planning
standards and guides until parameters are proven and
included in approved federal, allied, MIL-STD-188-XXX, or
DoD adopted commercial standards.
4. MIL-STD-187-XXX standards provide uniform guidance for the
design of the evolving and future Defense Information System.
Providing this guidance at the concept engineering stage will
help to minimize ineffective designs and costly interoperability
problems at later stages of implementation, as well as to assure
utilization of appropriate advances in technology. Planning
standards are developed considering present and future plans for
the Defense Information System, commercial systems (both national
and international) , and NATO and other allied military systems.
5.
The treatment of automatic link establishment (ALE) in
MIL-STD-188-141 provides the technical foundation upon which this
document rests. The second generation ALE system was one of the
adaptive high frequency (HF) radio features developed through a
MITRE effort in 1986.
The remainder of the original concept is
being documented in MIL-STD-187-721.
Therefore, a brief summary
of the basic principles of this ALE system is provided.
ii
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MIL-STD-187-721
6. The DrinciDal functions included in an automated HF
station are shown schematically in the figure on page iii.
This
diagram is structured along the lines of the 1S0 Open Systems
Interconnection Reference Model, with functions at each layer
supporting higher layers and using lower layers.
Other
Data Link
Protocols
““~
Functions:
Channel Selection
Link Establishment &
Termination
Data Transfer
Passive LQA, Polling
LQA Reporting
DATA
Messaqe Sections:
LINK
DBM, DTM, AMD, LQA,
LAYER
Time Exchange
Selective Calling
(ALE frame)
(Individual, Net,
Group, Sound)
Linking Prot (opt.)
FEC
PHYSICAL
Data Modem ALE Modem
LAYER
Transceiver
. . . . . - . ..— . ..
Functional nlerarcny or
aucomacea HF srarlon.
7. MIL-STD-188-141 specifies a basic HF radio, along with a
set of robust physical and data link layer functions for ALE.
The ALE modem employs 8-ary frequency shift keying (FSK) with 8
millisecond (ins)tones; the 3-bit symbols are sent at a rate of
iii
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MIL-STD-187-721
125 per second, giving a raw data rate of 375 bits per second
(bps).
Forward error correction (FEc) coding is applied to the
24-bit ALE words used at the data link layer; a (24,12) Golay
code is applied to each (12-bit) half of the 24-bit ALE word,
producing two 24-bit results.
These two 24-bit Golay words are
then interleaved bit by bit,
and a stuff bit is appended to
produce a 49-bit word to be transmitted. Finally, each 49-bit
word is sent three times,
which allows the receiver to correct
some errors using 2 of 3 majority voting.
8. At the receiver, received bits from the modem are
(conceptually) shifted into a 99-bit register. Majority voting
among the outputs of this shift register yields a 48-bit
“majority word” (stuff bits are discarded), which is de-
interleaved to produce two 24-bit Golay words. These are
delivered to the Golay decoder, which attempts to recover a 24-
bit ALE word.
9.
Because no bits in the ALE word are spent on
synchronization, the acquisition of word sync in this system
employs a series of tests on the prospective word after each
received symbol (tri-bit) is shifted in.
First, the number of
unanimous votes in the majority vote decoder must exceed a
threshold. Next, the Golay decoder must successfully decode both
halves of the 48-bit word. Finally, the resulting 24-bit ALE
word must be acceptable to the ALE protocol module. Once word
sync has been achieved, it is automatically tracked for the
remainder of the transmission using these same tests.
10. The MIL-STD-188-141 data link layer comprises several
sublayers.
The lowest sublayer is concerned with error detection
and correction (FEC sublayer) .
Above this is an optional
protection sublayer (linking protection), which protects layers
above it from unwanted interference. The ALE protocol is divided
into three sublayers in the figure on page iii:
the lowest
manages the exchange of ALE frames among stations that are
specified using a standardized addressing structure; the next
deals with orderwire and other message sections embedded within
ALE frames; the highest contains the data link layer functions
apparent to users, such as channel selection, link establishment,
and orderwire communications.
11. The contents of this document provide the technical
parameters for the functions and features of advanced adaptive HF
radio, and provide logical and cohesive guidelines for both
industry and the Government.
iv
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MIL-STD-187-721
CONTENTS
PARAGRAPH
m
1.
1.1
1.2
1.3
2.
2.1
2.1.1
2.1.2
2.2
2.3
3.
3.1
3.2
3.3
4.
4.1
4.2
SCOPE . . . . . . . . . . . . . . . . . . . . .
Scope . . . . . . . . . . . . . . . . . .
Applicability . . . . . . . . . . . . . .
Application guidance . . . . . . . . . . .
APPLICABLE DOCUMENTS . . . . . . . . . . . . . .
Government documents . . . . . . . . . . .
Specifications, standards, and handbooks .
Other Government documents, drawings, and
publications. . . . . . . . . . . . . . .
Non-Government publications . . . . . . .
Order of precedence . . . . . . . . . . .
DEFINITIONS . . . . . . . . . . . - . . . . . .
Terms . . . . . . . . . . . . . . . . - .
Abbreviations and acronyms . . . . . . . .
Timing symbols. . . . . . . . . . . . . .
GENERAL REQUIREMENTS . . . . . . . . . . . . . .
Data link sublayers . . . . . . . . . . .
Linkina protection . . . . . . . . . . . .
. . .
..”.
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
. . .
4.2.1
Linkin~ ~rotection application levels . . . . .
4.2.1.1
AL-O (unprotected application level) . . . . . .
4.2.1.2
AL-1 (unclassified application level) . . . . .
4.2.1.3 AL-2 (unclassified enhanced application level) .
4.2.1.4
AL-3 (unclassified but sensitive application
level) . . . . . . . . . . . . . . . . . . . . .
4.2.1.5
AL-4 (classified application level) . . . . . .
4.2.2
Protocol transparency . . . . . . . . . . . . .
4.2.3
Transmit processing . . . . . . . . . . . . . .
4.2.4
Receive processing.. . . . . . . . . . . . . .
4.3 Time of day (TOD) synchronization . . . . . . .
4.4
Link quality functions . . . . . . . . . . . . .
4.5 Advanced link quality functions . . . . . . . .
4.6
Networking functions . . . . . . . . . . . . . .
4.7
Interface to link controllers . . . . . . . . .
4.8
Network management.. . . . . . . . . . . . . .
4.9
Multi-media networking . . . . . . . . . . . . .
4.10
Special requirements . . . . . . . . . . . . . .
5. DETAILED REQUIREMENTS . . . . . . . . . . . . . . . .
5.1 Linking protection.. . . . . . . . . . . . . .
5.1.1 Linking protection control
module . . . . . . .
5.1.1.1
Scrambler interfaces . . . . . . . . . . . . . .
5.1.1.2
Timeanddate . . . . . . . . . . . . . . . - .
5.1.1.2.1 Timeofdayentry . . . . . . . . . . . . - . .
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13
v
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