ISO 22642:2005

INTERNATIONAL ISO
STANDARD 22642
First edition
2005-07-15

Space data and information transfer
systems — TC (telecommand)
synchronization and channel coding
Systèmes de transfert des données et informations spatiales —
Synchronisation TC (télécommande) et codage de canal




Reference number
ISO 22642:2005(E)
©
ISO 2005

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ISO 22642:2005(E)
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ISO 22642:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 22642 was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as CCSDS
231.0-B-1, September 2003) and was adopted (without modifications except those stated in Clause 2 of this
International Standard) by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 13, Space data and information transfer systems.

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INTERNATIONAL STANDARD ISO 22642:2005(E)

Space data and information transfer systems —
TC (telecommand) synchronization and channel coding
1 Scope
This International Standard defines synchronization and channel coding schemes used with the telecommand
(TC) space data link protocol as defined in ISO 22664. These schemes are to be used over ground-to-space
or space-to-space communications links by space missions.
The scope and field of application are furthermore detailed in subclauses 1.1 and 1.2 of the enclosed CCSDS
publication.
2 Requirements
Requirements are the technical recommendations made in the following publication (reproduced on the
following pages), which is adopted as an International Standard:
CCSDS 231.0-B-1, September 2003, TC synchronization and channel coding.
For the purposes of international standardization, the modifications outlined below shall apply to the specific
clauses and paragraphs of publication CCSDS 231.0-B-1.
Pages i to v
This part is information which is relevant to the CCSDS publication only.
Page 1-5
Add the following information to the reference indicated:
[1] Document CCSDS 232.0-B-1, September 2003, is equivalent to ISO 22664:2005.
Page B-1
Add the following information to the reference indicated:
[B2] Document CCSDS 201.0-B-3, June 2000, is equivalent to ISO 12171:2002.
It has been agreed with the Consultative Committee for Space Data Systems that Subcommittee
ISO/TC 20/SC 13 will be consulted in the event of any revision or amendment of publication CCSDS 231.0-B-1.
To this end, NASA will act as a liaison body between CCSDS and ISO.

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ISO 22642:2005(E)
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ISO 22642:2005(E)









RECOMMENDATION FOR SPACE
DATA SYSTEM STANDARDS


TC SYNCHRONIZATION
AND CHANNEL CODING



CCSDS 231.0-B-1

BLUE BOOK


September 2003


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ISO 22642:2005(E)
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING
AUTHORITY


Issue: Blue Book, Issue 1
Date: September 2003
Location: Not Applicable


This document has been approved for publication by the Management Council of the
Consultative Committee for Space Data Systems (CCSDS) and represents the consensus
technical agreement of the participating CCSDS Member Agencies. The procedure for
review and authorization of CCSDS Recommendations is detailed in reference [B1], and the
record of Agency participation in the authorization of this document can be obtained from
the CCSDS Secretariat at the address below.



This Recommendation is published and maintained by:

CCSDS Secretariat
Office of Space Communication (Code M-3)
National Aeronautics and Space Administration
Washington, DC 20546, USA
CCSDS 231.0-B-1 Page i September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of member space Agencies. The Committee meets
periodically to address data systems problems that are common to all participants, and to
formulate sound technical solutions to these problems. Inasmuch as participation in the
CCSDS is completely voluntary, the results of Committee actions are termed
Recommendations and are not considered binding on any Agency.
This Recommendation is issued by, and represents the consensus of, the CCSDS Plenary
body. Agency endorsement of this Recommendation is entirely voluntary. Endorsement,
however, indicates the following understandings:
– Whenever an Agency establishes a CCSDS-related standard, this standard will be in
accord with the relevant Recommendation. Establishing such a standard does not
preclude other provisions which an Agency may develop.
– Whenever an Agency establishes a CCSDS-related standard, the Agency will provide
other CCSDS member Agencies with the following information:
• The standard itself.
• The anticipated date of initial operational capability.
• The anticipated duration of operational service.
– Specific service arrangements are made via memoranda of agreement. Neither this
Recommendation nor any ensuing standard is a substitute for a memorandum of
agreement.
No later than five years from its date of issuance, this Recommendation will be reviewed by
the CCSDS to determine whether it should: (1) remain in effect without change; (2) be
changed to reflect the impact of new technologies, new requirements, or new directions; or,
(3) be retired or canceled.
In those instances when a new version of a Recommendation is issued, existing CCSDS-
related Agency standards and implementations are not negated or deemed to be non-CCSDS
compatible. It is the responsibility of each Agency to determine when such standards or
implementations are to be modified. Each Agency is, however, strongly encouraged to direct
planning for its new standards and implementations towards the later version of the
Recommendation.
CCSDS 231.0-B-1 Page ii September 2003
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ISO 22642:2005(E)

CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING
FOREWORD
This document is a technical Recommendation for use in developing synchronization and
channel coding systems and has been prepared by the Consultative Committee for Space
Data Systems (CCSDS). The synchronization and channel coding concept described herein
is intended for missions that are cross-supported between Agencies of the CCSDS.
This Recommendation establishes a common framework and provides a common basis for
the synchronization and channel coding schemes to be used by space missions with the TC
Space Data Link Protocol (reference [1]) over ground-to-space and space-to-space
communications links. This Recommendation was developed from an older CCSDS
Recommendation [B2], which defines essentially the same schemes but in a slightly different
context.
This Recommendation does not change the major technical content defined in [B2], but the
presentation of the specification has been changed so that:
a) these schemes can be used to transfer any data over any space link in either direction;
b) all CCSDS space link protocols are specified in a unified manner;
c) the layered model matches the Open Systems Interconnection (OSI) Basic Reference
Model (reference [2]).
Together with the change in presentation, a few technical specifications in [B2] have been
changed in order to define all Space Data Link Protocols in a unified way. Also, some
technical terms in reference [B2] have been changed in order to unify the terminology used
in all the CCSDS Recommendations that define space link protocols and to define these
schemes as general communications schemes. These changes are listed in annex C of this
Recommendation.
Through the process of normal evolution, it is expected that expansion, deletion or
modification to this document may occur. This Recommendation is therefore subject to
CCSDS document management and change control procedures, as defined in the Procedures
Manual for the Consultative Committee for Space Data Systems. Current versions of
CCSDS documents are maintained at the CCSDS Web site:
http://www.ccsds.org/
Questions relating to the contents or status of this document should be addressed to the
CCSDS Secretariat at the address indicated on page i.
CCSDS 231.0-B-1 Page iii September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING

At time of publication, the active Member and Observer Agencies of the CCSDS were:

Member Agencies

– Agenzia Spaziale Italiana (ASI)/Italy.
– British National Space Centre (BNSC)/United Kingdom.
– Canadian Space Agency (CSA)/Canada.
– Centre National d’Etudes Spatiales (CNES)/France.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– National Aeronautics and Space Administration (NASA)/USA.
– National Space Development Agency of Japan (NASDA)/Japan.
– Russian Space Agency (RSA)/Russian Federation.

Observer Agencies

– Austrian Space Agency (ASA)/Austria.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– Centro Tecnico Aeroespacial (CTA)/Brazil.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– Communications Research Laboratory (CRL)/Japan.
– Danish Space Research Institute (DSRI)/Denmark.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Federal Service of Scientific, Technical & Cultural Affairs (FSST&CA)/Belgium.
– Hellenic National Space Committee (HNSC)/Greece.
– Indian Space Research Organization (ISRO)/India.
– Institute of Space and Astronautical Science (ISAS)/Japan.
– Institute of Space Research (IKI)/Russian Federation.
– KFKI Research Institute for Particle & Nuclear Physics (KFKI)/Hungary.
– MIKOMTEK: CSIR (CSIR)/Republic of South Africa.
– Korea Aerospace Research Institute (KARI)/Korea.
– Ministry of Communications (MOC)/Israel.
– National Oceanic & Atmospheric Administration (NOAA)/USA.
– National Space Program Office (NSPO)/Taipei.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.
CCSDS 231.0-B-1 Page iv September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING
DOCUMENT CONTROL

Document Title and Issue Date Status
CCSDS TC Synchronization and Channel September Original Issue
231.0-B-1 Coding, Issue 1 2003

CCSDS 231.0-B-1 Page v September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING

CONTENTS
Section Page
1 INTRODUCTION. 1-1

1.1 PURPOSE.1-1
1.2 SCOPE.1-1
1.3 APPLICABILITY.1-1
1.4 RATIONALE.1-1
1.5 DOCUMENT STRUCTURE.1-2
1.6 CONVENTIONS AND DEFINITIONS. 1-2
1.7 REFERENCES.1-4

2 OVERVIEW. 2-1

2.1 ARCHITECTURE.2-1
2.2 SUMMARY OF FUNCTIONS . 2-1
2.3 INTERNAL ORGANIZATION OF SUBLAYER. 2-3

3 BCH CODING . 3-1
3.1 INTRODUCTION.3-1
3.2 CODEBLOCK FORMAT.3-1
3.3 ENCODING PROCEDURE.3-1
3.4 FILL BITS.3-2
3.5 DECODING PROCEDURE.3-3

4 COMMUNICATIONS LINK TRANSMISSION UNIT . 4-1

4.1 INTRODUCTION.4-1
4.2 CLTU UNIT FORMAT. 4-1
4.3 CLTU RECEPTION LOGIC. 4-2

5 RANDOMIZER . 5-1

5.1 INTRODUCTION.5-1
5.2 RANDOMIZER DESCRIPTION.5-1
5.3 APPLICATION OF THE RANDOMIZER. 5-2

6 PHYSICAL LAYER OPERATIONS PROCEDURES. 6-1

6.1 INTRODUCTION.6-1
6.2 DATA FORMATS.6-1
6.3 CARRIER MODULATION MODES . 6-2
6.4 PLOP-1.6-2
CCSDS 231.0-B-1 Page vi September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING

CONTENTS (continued)
Section Page
6.5 PLOP-2.6-3

7 MANAGED PARAMETERS . 7-1

7.1 OVERVIEW OF MANAGED PARAMETERS . 7-1
7.2 MANAGED PARAMETERS FOR BCH CODING . 7-1
7.3 MANAGED PARAMETERS FOR CLTU . 7-1
7.4 MANAGED PARAMETERS FOR THE RANDOMIZER . 7-2
7.5 MANAGED PARAMETERS FOR PLOPS. 7-2

ANNEX A ACRONYMS AND TERMS . A-1
ANNEX B INFORMATIVE REFERENCES.B-1
ANNEX C SERVICE DEFINITION. C-1
ANNEX D CHANGES FROM REFERENCE [B2]. D-1

Figure
1-1 Bit Numbering Convention. 1-4
2-1 Relationship with OSI Layers. 2-1
2-2 Internal Organization of the Sublayer at the Sending End . 2-3
3-1 BCH Codeblock Format . 3-1
3-2 (63,56) Modified BCH Code Generator . 3-2
4-1 Components of the CLTU. 4-1
4-2 CLTU Reception State Diagram (Receiving End) . 4-2
5-1 Bit Transition Generator Logic Diagram. 5-2
6-1 Sequence of CMMs Composing PLOP-1. 6-3
6-2 Sequence of CMMs Composing PLOP-2. 6-4

Table
4-1 CLTU Reception States (Receiving End). 4-3
4-2 CLTU Reception Events (Receiving End) . 4-4
6-1 Carrier Modulation Modes . 6-2
7-1 Managed Parameters for BCH Coding . 7-1
7-2 Managed Parameters for CLTU. 7-1
7-3 Managed Parameters for Randomizer. 7-2
7-4 Managed Parameters for PLOPs. 7-2
D-1 Terms That Have Been Changed from Reference [B2]. D-2

CCSDS 231.0-B-1 Page vii September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING

1 INTRODUCTION
1.1 PURPOSE
The purpose of this Recommendation is to specify synchronization and channel coding
schemes used with the Telecommand (TC) Space Data Link Protocol [1]. These schemes are
to be used over ground-to-space or space-to-space communications links by space missions.
1.2 SCOPE
This Recommendation defines synchronization and channel coding schemes in terms of:
a) the services provided to the users of this specification;
b) data formats; and
c) the procedures performed to generate and process the data formats.
It does not specify:
a) individual implementations or products;
b) the methods or technologies required to perform the procedures; or
c) the management activities required to configure and control the system.
1.3 APPLICABILITY
This Recommendation applies to the creation of Agency standards and to the future data
communications over space links between CCSDS Agencies in cross-support situations.
This Recommendation includes comprehensive specification of the data formats and
procedures for inter-Agency cross support. It is neither a specification of, nor a design for,
real systems that may be implemented for existing or future missions.
The Recommendation specified in this document is to be invoked through the normal
standards programs of each CCSDS Agency, and is applicable to those missions for which
cross support, based on capabilities described in this Recommendation, is anticipated.
Where mandatory capabilities are clearly indicated in sections of this Recommendation, they
must be implemented when this document is used as a basis for cross support. Where
options are allowed or implied, implementation of these options is subject to specific
bilateral cross support agreements between the Agencies involved.
1.4 RATIONALE
The CCSDS believes it is important to document the rationale underlying the
recommendations chosen, so that future evaluations of proposed changes or improvements
will not lose sight of previous decisions.
CCSDS 231.0-B-1 Page 1-1 September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING

1.5 DOCUMENT STRUCTURE
This document is divided into seven numbered sections and four annexes:
a) section 1 presents the purpose, scope, applicability and rationale of this
Recommendation and lists the conventions, definitions, and references used
throughout the Recommendation;
b) section 2 provides an overview of synchronization and channel coding;
c) section 3 specifies the Bose-Chaudhuri-Hocquenghem (BCH) coding;
d) section 4 specifies the Communications Link Transmission Unit (CLTU);
e) section 5 specifies the randomizer;
f) section 6 specifies the Physical Layer Operations Procedures (PLOPs);
g) section 7 lists the managed parameters associated with synchronization and channel
coding;
h) annex A lists acronyms and terms used within this document;
i) annex B provides a list of informative references;
j) annex C defines the service provided to the users;
k) annex D lists the changes from the older CCSDS Recommendation [B2].
1.6 CONVENTIONS AND DEFINITIONS
1.6.1 DEFINITIONS
1.6.1.1 Definitions from the Open Systems Interconnection (OSI) Basic Reference
Model
This Recommendation makes use of a number of terms defined in reference [2]. The use of
those terms in this Recommendation shall be understood in a generic sense; i.e., in the sense
that those terms are generally applicable to any of a variety of technologies that provide for
the exchange of information between real systems. Those terms are as follows:
a) Data Link Layer;
b) Physical Layer;
c) service;
d) service data unit.
CCSDS 231.0-B-1 Page 1-2 September 2003
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ISO 22642:2005(E)

CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING
1.6.1.2 Definitions from OSI Service Definition Conventions
This Recommendation makes use of a number of terms defined in reference [3]. The use of
those terms in this Recommendation shall be understood in a generic sense; i.e., in the sense
that those terms are generally applicable to any of a variety of technologies that provide for
the exchange of information between real systems. Those terms are as follows:
a) indication;
b) primitive;
c) request;
d) service provider;
e) service user.
1.6.1.3 Terms Defined in This Recommendation
For the purposes of this Recommendation, the following definitions apply. Many other terms
that pertain to specific items are defined in the appropriate sections.
asynchronous: not synchronous.
Mission Phase: a period of a mission during which specified communications
characteristics are fixed. The transition between two consecutive mission phases may cause
an interruption of the communications services.
Physical Channel: a stream of bits transferred over a space link in a single direction.
space link: a communications link between a spacecraft and its associated ground system or
between two spacecraft. A space link consists of one or more Physical Channels in one or
both directions.
synchronous: a sequence of events occurring in a fixed time relationship (within specified
tolerance) to another sequence of events.
CCSDS 231.0-B-1 Page 1-3 September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING

1.6.2 NOMENCLATURE
The following conventions apply throughout this Recommendation:
a) the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
b) the word ‘should’ implies an optional, but desirable, specification;
c) the word ‘may’ implies an optional specification;
d) the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
1.6.3 CONVENTIONS
In this document, the following convention is used to identify each bit in an N-bit field. The
first bit in the field to be transmitted (i.e., the most left justified when drawing a figure) is
defined to be ‘Bit 0’; the following bit is defined to be ‘Bit 1’ and so on up to ‘Bit N-1’.
When the field is used to express a binary value (such as a counter), the Most Significant Bit
(MSB) shall be the first transmitted bit of the field, i.e., ‘Bit 0’ (see figure 1-1).
BIT N-1
BIT 0
N-BIT DATA FIELD
FIRST BIT TRANSMITTED = MSB

Figure 1-1: Bit Numbering Convention
In accordance with standard data-communications practice, data fields are often grouped into
8-bit ‘words’ which conform to the above convention. Throughout this Recommendation,
such an 8-bit word is called an ‘octet’. The numbering for octets within a data structure
starts with 0. By CCSDS convention, all ‘spare’ bits shall be permanently set to ‘0’.
1.7 REFERENCES
The following documents contain provisions which, through reference in this text, constitute
provisions of this Recommendation. At the time of publication, the editions indicated were
valid. All documents are subject to revision, and users of this Recommendation are
encouraged to investigate the possibility of applying the most recent editions of the
documents indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS Recommendations.
CCSDS 231.0-B-1 Page 1-4 September 2003
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ISO 22642:2005(E)
CCSDS RECOMMENDATION FOR TC SYNCHRONIZATION AND CHANNEL CODING
[1] TC Space Data Link Protocol. Recommendation for Space Data Systems Standards,
CCSDS 232.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
[2] Information Technology—Open Systems Interconnection—Basic Reference Model:
The Basic Model. International Standard, ISO/IEC 7498-1. 2nd ed. Geneva: ISO,
1994.
[3] Information Technology—Open Systems Interconnection
...