ISO 22641:2012 宇宙データおよび情報転送システム— TM（テレメトリ）同期およびチャネルコーディング | ページ 5

1.1 目的

この推奨規格の目的は、TM スペース データ リンク プロトコル (参考文献 [1]) または AOS スペース データ リンク プロトコル (参考文献 [2]) で使用される同期およびチャネル コーディング スキームを指定することです。これらのスキームは、宇宙ミッションによって宇宙から地上へ、または宇宙から宇宙への通信リンク上で使用されます。

1.6.1 定義

1.6.1.1 Open System Interconnection (OSI) 基本参照モデルからの定義

この推奨規格では、参考文献 [3] で定義されている多数の用語が使用されています。この推奨規格におけるこれらの用語の使用は、一般的な意味で理解されるものとします。つまり、これらの用語は、実際のシステム間の情報交換を提供するさまざまなテクノロジのいずれにも一般的に適用できるという意味です。これらの用語は次のとおりです。

• a)データリンク層。
• b)物理層。
• c)サービス。
• d)サービスデータユニット。

1.6.1.2 OSI サービス定義規則による定義

この推奨規格では、参考文献 [4] で定義されている多くの用語が使用されています。この推奨規格におけるこれらの用語の使用は、一般的な意味で理解されるものとします。つまり、これらの用語は、実際のシステム間の情報交換を提供するさまざまなテクノロジのいずれにも一般的に適用できるという意味です。これらの用語は次のとおりです。

• a)表示。
• b)原始的。
• c)リクエスト。
• d)サービスプロバイダー。
• e)サービス利用者。

1 INTRODUCTION

1.2 SCOPE

This Recommended Standard 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 Recommended Standard applies to the creation of Agency standards and to the future data communications over space links between CCSDS Agencies in cross-support situations. This Recommended Standard 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 Recommended Standard 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 Recommended Standard is anticipated. Where mandatory capabilities are clearly indicated in sections of this Recommended Standard, 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.

1.5 DOCUMENT STRUCTURE

This document is divided into eleven numbered sections and seven annexes:

• a) section 1 presents the purpose, scope, applicability and rationale of this Recommended Standard and lists the conventions, definitions, and references used throughout the document;
• b) section 2 provides an overview of synchronization and channel coding;
• c) section 3 specifies convolutional coding;
• d) section 4 specifies Reed-Solomon coding;
• e) section 5 concatenated coding;
• f) section 6 specifies Turbo coding;
• g) section 7 specifies low-density parity-check coding;
• h) section 8 specifies the frame synchronization scheme;
• i) section 9 specifies the Pseudo-Randomizer;
• j) section 10 specifies the allowed lengths of Transfer Frames;
• k) section 11 lists the managed parameters associated with synchronization and channel coding;
• l) annex A defines the service provided to the users;
• m) annex B discusses security issues related to TM Channel Coding;
• n) annex C provides the generator matrix circulant table applicable to rate-223/255 LDPC coding (7.3);
• o) annex D lists acronyms and terms used within this document;
• p) annex E provides a list of informative references;
• q) annex F provides information on transformation between the Berlekamp (dual basis) and Conventional representations;
• r) annex G provides information on Reed-Solomon coefficients;
• s) annex H lists the changes from relevant previously published CCSDS Recommended Standards (references [E2] and [E3]).

1.6 CONVENTIONS AND DEFINITIONS

1.6.1.3 Definition of Terms Used in This Recommended Standard

For the purposes of this Recommended Standard, the following definitions apply. Many other terms that pertain to specific items are defined in the appropriate sections.

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.

1.6.2 NOMENCLATURE

The following conventions apply for the normative specifications in this Recommended Standard:

• 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).

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 Recommended Standard, such an 8-bit word is called an 'octet'.

The numbering for octets within a data structure starts with '0'.

1.7 PATENTED TECHNOLOGIES

The CCSDS draws attention to the fact that it is claimed that compliance with this document may involve the use of patents concerning Turbo Coding (section 6) and Low-Density Parity-Check Coding (section 7).

The CCSDS takes no position concerning the evidence, validity, and scope of these patent rights.

The holders of these patent rights have assured the CCSDS that they are willing to negotiate licenses under reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect, the statements of the holders of these patent rights are registered with CCSDS. Information can be obtained from the CCSDS Secretariat at the address indicated on page i. Contact information for the holders of these patent rights is provided in annex B.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights other than those identified above. The CCSDS shall not be held responsible for identifying any or all such patent rights.

1.8 REFERENCES

The following documents contain provisions which, through reference in this text, constitute provisions of this Recommended Standard. At the time of publication, the editions indicated were valid. All documents are subject to revision, and users of this Recommended Standard 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 Recommended Standards.

ANNEX E

INFORMATIVE REFERENCES