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Doc 9871 First Edition

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ICAO Technical Provisions for Mode S Servicesand Extended Squitter

    ASP

    WP B/11-04

    Agenda Item 3.1

    13 September 2006

AERONAUTICAL SURVEILLANCE PANEL (ASP)

    DOC 9871 FIRST EDITION

    (Prepared by the TSG )

    SUMMARY

    This working paper presents the first version of Doc 9871. Tracked changes indicate the revisions that were made to the document as a result of WG-B actions at Montreal and TSG actions at and after

    Toulouse.

    Doc 9871

    Technical Provisions for Mode S Services

    and

    Extended Squitter

    First Edition Rev. 0 2006

    INTERNATIONAL CIVIL AVIATION ORGANIZATION

    i

    AMENDMENTS

    The issue of amendments is announced regularly in the ICAO Journal and in the monthly

    Supplement to the Catalogue of ICAO Publications and Audio-visual Training Aids,

    which holders of this publication should consult. The space below is provided to keep a

    record of such amendments.

    AMENDMENTS CORRIGENDA

    No. Date Date Entered No. Date Date Entered

     applicable entered by applicable entered by

     ii

    FOREWORD

    The purpose of this manual is to specify technical provisions for the formats and associated protocols used in Mode S services and extended squitter. These detailed technical provisions supplement requirements contained in Annex 10 Aeronautical Telecommunications, Volume III Communication Systems,

    Volume IV Surveillance Radar and Collision Avoidance Systems, and are necessary to ensure global

    interoperability.

    The manual also includes implementation guidelines as well as information on future Mode S and extended squitter services that are under development.

    The provision of Mode S services, specified in this document, include the following:

    a) data formats for transponder registers;

    b) Formats for Mode S specific protocols:

    1. traffic information broadcast; and

    2. dataflash;

    a) Mode S broadcast protocols, including:

    1) uplink broadcast; and

    2) downlink broadcast.

    Formats and protocols for extended squitter automatic dependent surveillance broadcast (ADS-B)

    messages are also included since registers are defined for each of these messages. Those registers are assigned so that the extended squitter messages can be read out on demand by a ground interrogator, in addition to being delivered via ADS-B broadcast.

    This manual has been developed by the Surveillance and Conflict Resolution Systems Panel (SCRSP). Comments on this manual from States and other parties outside ICAO would be appreciated. Comments should be addressed to:

The Secretary General

    International Civil Aviation Organization

    999 University Street

    Montreal, Quebec

    Canada H3C 5H7

     iii

    TABLE OF CONTENTS

    Foreword ........................................................................................................................................................ iii

    Glossary .......................................................................................................................................................... v

    Acronyms ...................................................................................................................................................... vii

Chapter 1: Introduction .......................................................................................................................... 1-1

Chapter 2: Overview of Mode S Services and Extended Squitter Version 0............................................. 2-1

Chapter 3: Overview of Extended Squitter Version 1.............................................................................. 3-1

    Appendix A. Data/Message Formats and Control Parameters for Mode S Specific Services and

     Extended Squitter Version 0................................................................................................. A-1

Appendix B. Provisions for Extended Squitter Version 1 .......................................................................... B-1

Appendix C. Implementation Guidelines .................................................................................................. C-1

Appendix D. Services under development ................................................................................................. D-1

    iv

    GLOSSARY

Automatic dependent surveillance broadcast (ADS-B) IN. A function that receives surveillance data from

    ADS-B out data sources.

Automatic dependent surveillance broadcast (ADS-B) OUT. A function on an aircraft or vehicle that

    periodically broadcasts its state vector (position and velocity) and other information derived from on-board

    systems in a format suitable for ADS-B in capable receivers.

    Air-initiated Comm-B (AICB) protocol. A procedure initiated by a Mode S aircraft installation for delivering a

    Comm-B message to the ground.

    Aircraft. The term aircraft may be used to refer to Mode S emitters (e.g. aircraft/vehicles), where appropriate.

    Aircraft data link processor (ADLP). An aircraft-resident processor that is specific to a particular air-ground

    data link (e.g. Mode S) and which provides channel management, and segments and/or reassembles

    messages for transfer. It is connected on one side to aircraft elements common to all data link systems and

    on the other side to the air-ground link itself.

    Aircraft address. A unique combination of 24 bits available for assignment to an aircraft for the purpose of air-

    ground communications, navigation and surveillance.

    Aircraft/Vehicle. May be used to describe either a machine or device capable of atmospheric flight, or a vehicle

    on the airport surface movement area (i.e. runways and taxiways).

    BDS Comm-B Data Selector. The 8-bit BDS code determines the transponder register whose contents are to be

    transferred in the MB field of a Comm-B reply. It is expressed in two groups of 4 bits each, BDS1 (most

    significant 4 bits) and BDS2 (least significant 4 bits).

    Broadcast. The protocol within the Mode S system that permits uplink messages to be sent to all aircraft in the

    coverage area, and downlink messages to be made available to all interrogators that have the aircraft

    wishing to send the message under surveillance.

    Capability Report. Information identifying whether the transponder has a data link capability as reported in the

    capability (CA) field of an all-call reply or squitter transmission (see Data link capability report).

    Close-out. A command from a Mode S interrogator that terminates a Mode S link layer communications

    transaction.

    Comm-A. A 112-bit interrogation containing the 56-bit MA message field. This field is used by the uplink

    standard length message (SLM) and broadcast protocols.

    Comm-B. A 112-bit reply containing the 56-bit MB message field. This field is used by the downlink SLM,

    ground-initiated and broadcast protocols.

    Comm-C. A 112-bit interrogation containing the 80-bit MC message field. This field is used by the uplink

    extended length message (ELM) protocol.

    Comm-D. A 112-bit reply containing the 80-bit MD message field. This field is used by the downlink ELM

    protocol.

    Data link capability report. Information in a Comm-B reply identifying the complete Mode S communication

    capabilities of the aircraft installation

    Downlink. A term referring to the transmission of data from an aircraft to the ground. Mode S air-to-ground

    signals are transmitted on the 1 090 MHz reply frequency channel

     v

    Frame. The basic unit of data transfer at the link level. A frame can include from one to four Comm-A or

    Comm-B segments, from two to sixteen Comm-C segments, or from one to sixteen Comm-D segments.

    General Formatter/Manager (GFM). The aircraft function responsible for formatting messages to be inserted

    in the transponder registers. It is also responsible for detecting and handling error conditions such as the loss

    of input data.

    Ground Data Link Processor (GDLP). A ground-resident processor that is specific to a particular air-ground

    data link (e.g. Mode S) and which provides channel management, and segments and/or reassembles

    messages for transfer. It is connected on one side (by means of its data circuit terminating equipment (DCE))

    to ground elements common to all data link systems, and on the other side to the air-ground link itself.

    Ground-initiated Comm-B (GICB). The ground-initiated Comm-B protocol allows the interrogator to extract

    Comm-B replies containing data from one of the 255 transponder registers within the transponder in the MB

    field of the reply.

    Ground-initiated protocol. A procedure initiated by a Mode S interrogator for delivering standard length (via

    Comm-A) or extended length (via Comm-C) messages to a Mode S aircraft installation.

    Horizontal Integrity Limit (HIL). The radius of a circle in the horizontal plane (i.e. the plane tangent to the WGS-84 ellipsoid), with its center being the true position, which describes the region which is assured to contain the indicated horizontal position.

    Horizontal Protection Limit (HPL). The radius of a circle in the horizontal plane (i.e. the plane tangent to the WGS-84 ellipsoid), with its center being the true position, which describes the region which is assured to contain the indicated horizontal position.

    The terms HPL and HIL (Horizontal Integrity Limit) are used interchangeably in various documents.

    Mode S broadcast protocols. Procedures allowing standard length uplink or downlink messages to be received

    by more than one transponder or ground interrogator, respectively.

    Mode S packet. A packet conforming to the Mode S subnetwork standard, designed to minimize the bandwidth

    required from the air-ground link. ISO 8208 packets may be transformed into Mode S packets and vice

    versa.

    Mode S Specific Protocol (MSP). A protocol that provides a restricted datagram service within the Mode S sub-

    network

    Mode S specific services. A set of communication services provided by the Mode S system which are not

    available from other air- ground subnetworks and therefore not interoperable

    Packet. The basic unit of data transfer among communications devices within the network layer (e.g. an

    ISO 8208 packet or a Mode S packet).

    Required Navigation Performance (RNP). A statement of the navigation performance accuracy necessary for

    operation within a defined airspace

    Segment. A portion of a message that can be accommodated within a single MA/MB field in the case of an

    SLM, or a single MC/ MD field in the case of an ELM. This term is also applied to the Mode S

    transmissions containing these fields.

Standard Length Message (SLM). An exchange of digital data using selectively addressed Comm-A

    interrogations and/or Comm-B replies.

    Subnetwork. An actual implementation of a data network that employs a homogeneous protocol and addressing

    plan and is under the control of a single authority

     vi

    Timeout. The cancellation of a transaction after one of the participating entities has failed to provide a required

    response within a pre-defined period of time.

    Uplink. A term referring to the transmission of data from the ground to an aircraft. Mode S ground-to-air

    signals are transmitted on the 1 030 MHz interrogation frequency channel

     vii

    ACRONYMS

    ACAS Airborne collision avoidance system ADLP Airborne data link processor ADS-B Automatic dependent surveillance-broadcast

    ATN Aeronautical telecommunication network ATS Air traffic service

    A/V Aircraft/vehicle

    BITE Built-in test equipment BDS Comm-B data selector

    CFDIU Centralized fault display interface unit

    CPR Compact position reporting ELM Extended length message

    ES Extended squitter

    FCC Flight control computer

    FCU Flight control unit

    FMS Flight management system

    GDLP Ground data link processor GICB Ground-initiated Comm-B GFM General formatter/manager GNSS Global navigation satellite system HAE Height above the ellipsoid HIL Horizontal Integrity Limit HPL Horizontal Protection Limit II Interrogator identifier

    LSB Least significant bit

    MA Message, Comm-A

    MB Message, Comm-B

    MC Message, Comm-C

    MD Message, Comm-D

    MOPS Minimum operational performance standards

    MSB Most Significant Bit

    MSP Mode S specific protocol MSSS Mode S specific services NACNavigational accuracy category position P

    NACNavigational accuracy category velocity V

    NIC Navigation integrity category NUC Navigational uncertainty category position PNUC Navigational uncertainty category rate R

    RNP Required navigation performance SAF Single antenna flag

    SARPs Standards and Recommended Practices SSE Mode S specific services entity SI Surveillance identifier

    SIL Surveillance integrity level SLM Standard length message

    SPI Special position identification SSR Secondary surveillance radar TIS Traffic information service TIS-B Traffic information service-broadcast

    UTC Coordinated universal time

     viii

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