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MIL-STD-187_721B.026564.pdf
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MIL-STD-187_721B.026564.pdf
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Mad
MlL-STO-l87-721B
4 APRIL 1994
MILITARY STANDARD
PLANNING AND GUIDANCE
STANDARD FOR AUTOMATED
CONTROL APPLIQUE FOR
HF RADIO
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MIL-STD-187-721B
FOREWORD
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-OST, Fort
Huachuca, Arizona
85613-5300, by using the self-addressed
Standardization Document Improvement Proposal (DD Form 1426)
aPPearin9 at the end of this document or by letter.
.
3.
In accordance with DoD Instruction 4630.8, it is DoD
policy that all forces for joint and combined operations be
supported through compatible, interoperable, and
integrated C31
systems.
Furthermore, all C31 eystems developed for use by U.S.
forces are considered to be for joint use.
The Director, DISA,
serves as the DoD single point of contact for developing
information technology standards to achieve interoperability and
compatibility. All C31 systems and equipment shall conform to
technical and procedural standards for compatibility and
interoperability, as developed or recommended by the DISA.
4. Military Standards in the 187 series (MIL-STD-187-XXX)
address telecommunications design parameters based on evolving
●
technologies and concepts that may be subject to change.
These
planning standards differ from military standards in the 188
series (MIL-STD-188-XXX) which address telecommunications design
parameters based on mature technologies.
Nothing in a
MIL-STD-187 series document is mandatory unless invoked in a
contract,
and then only to the extent of the contractual
agreement.
5.
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.
These planning standards may be based
on,
or make reference to, draft or mature American National
Standards Institute (ANSI) standards, International
telecommunications Union - Telecommunications (ITU-T)
recommendations,
International Organization for Standardization
(1S0) standards, NATO standardization agreements (STANAGS), and
other standards, wherever applicable.
MIL-STD-187-XXX standards
provide uniform guidance for the design of the evolving and
future Defense Information System. Providing this guidance as
early as possible will minimize ineffective designs and costly
interoperability problems at later stages of implementation. It
will also help to assure utilization of appropriate advances in
technology.
ii
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MIL-STD-187-721B
.
6. The treatment of automatic link establishment (ALE) in
MIL-STD-188-141 providee 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 baeic principles of this ALE system is provided.
7. The principal functions included in an automated HF
station are shown schematically on the figure below. 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.
8. 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
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 ie 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.
At the receiver, received bits from the modem are
(co~~eptually) shifted into a 99-bit register.
Majority voting
among the outputs of this ehift regieter 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.
10.
Because no bits in the ALE word are spent on
synchronization, the acquisition of word sync in this system
employs a series of teste 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
halvee 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.
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MIL-STD-187-721B
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 hierarchv
of an automated HF station.
11. 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 on the figure above:
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; and the
●
✎
●
iv
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MIL-STD-187-721B
highest contains the data link layer functions apparent to usere,
such as channel eelection, link eetabliehment, and orderwire
communication.
12. 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.
13. The technical parameters of this standard have not been
verified by testing or implementation.
Carefull engineering,
desk top modeling, and simulation are the source of these
parameters.
The preparing activity and the custodians are
confident that the technolgy is definitively developed and is
technically sound.
Users of this standard are reguested to
inform the preparing activity and the Lead Standardization
Activity (see address below) of planned implementations, status
of those implementations, and any problems encountered in
apPlYin9 this Standard.
Preparing Activity
U.S. Army Information Syetems
@
Engineering Command
ATTN :
ASQB-OST
Fort Huachuca,
AZ 85613-5300
Lead Standardization Activity
Joint Interoperability and
Engineering Organization
ATTN :
TBBF
Fort Monmouth, NJ 07703-5613
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