SIST ETS 300 938 E1:2003

Digital cellular telecommunications system; Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 5.0.1)

This European Telecommunication Standard defines a data link layer pro tocol to be used for signalling, and possibly also for other applicati ons, on the Mobile Station (MS) Base Station (BS) interface.

Digitalni celični telekomunikacijski sistem – Mobilna postaja – Vmesnik sistema bazne postaje (MS-BSS) – Specifikacija podatkovne povezovalne plasti (GSM 04.06, različica 5.0.1)

General Information

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.070.50 - Global System for Mobile Communication (GSM)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI ETS 300 938 ed.1 (1997-04) - Digital cellular telecommunications system; Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 5.0.1)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 938 E1:2003
01-december-2003
'LJLWDOQLFHOLþQLWHOHNRPXQLNDFLMVNLVLVWHP±0RELOQDSRVWDMD±9PHVQLNVLVWHPD
ED]QHSRVWDMH06%66±6SHFLILNDFLMDSRGDWNRYQHSRYH]RYDOQHSODVWL*60
UD]OLþLFD
Digital cellular telecommunications system; Mobile Station - Base Station System (MS -
BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 5.0.1)
Ta slovenski standard je istoveten z: ETS 300 938 Edition 1
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
SIST ETS 300 938 E1:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 938 E1:2003

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SIST ETS 300 938 E1:2003
EUROPEAN ETS 300 938
TELECOMMUNICATION April 1997
STANDARD
Source: ETSI TC-SMG Reference: DE/SMG-030406Q
ICS: 33.020
Key words: Digital cellular telecommunications system, Global System for Mobile communications (GSM)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
Digital cellular telecommunications system;
Mobile Station - Base Station System (MS - BSS) interface;
Data Link (DL) layer specification
(GSM 04.06 version 5.0.1)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: [e-mail]
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1997. All rights reserved.

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Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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Contents
Foreword .7
0 Scope .9
0.1 Normative references .9
0.2 Abbreviations .9
1 General.10
2 Frame structure for peer-to-peer communication .11
2.1 General .11
2.2 Frame delimitation and fill bits .13
2.3 Address field .13
2.4 Control field.13
2.5 Length indicator field.13
2.6 Information field .13
2.7 Transparency.14
2.8 Format convention .14
2.8.1 Numbering convention .14
2.8.2 Order of bit transmission .14
2.8.3 Field mapping convention .14
3 Elements of procedures and formats of fields for Data Link Layer peer-to-peer communication.15
3.1 General .15
3.2 Address field format.15
3.3 Address field variables.15
3.3.1 Address field extension bit (EA) .15
3.3.2 Command/response field bit (C/R).15
3.3.3 Service access point identifier (SAPI) .16
3.4 Control field formats.16
3.4.1 Information transfer format - I .16
3.4.2 Supervisory format - S.16
3.4.3 Unnumbered format - U .16
3.5 Control field parameters and associated state variables.17
3.5.1 Poll/Final bit.17
3.5.2 Multiple frame operation - variables and sequence numbers .17
3.5.2.1 Modulus .17
3.5.2.2 Send state variable V(S).17
3.5.2.3 Acknowledge state variable V(A).18
3.5.2.4 Send sequence number N(S).18
3.5.2.5 Receive state variable V(R).18
3.5.2.6 Receive sequence number N(R) .18
3.5.2.7 Other parameters and variables.18
3.5.3 Unacknowledged operation variables and parameters .18
3.6 Length indicator field format .19
3.7 Length indicator field variables .19
3.7.1 Length indicator field extension bit (EL) .19
3.7.2 More data bit (M) .19
3.7.3 Length indicator (L) .19
3.8 Commands and responses.19
3.8.1 Information (I) commands .20
3.8.2 Set asynchronous balanced mode (SABM) command .20
3.8.3 Disconnect (DISC) command.21
3.8.4 Unnumbered information (UI) command.21
3.8.5 Receive ready (RR) command/response .21
3.8.6 Reject (REJ) command/response .22
3.8.7 Receive not ready (RNR) command/response .22
3.8.8 Unnumbered acknowledgement (UA) response .22

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3.8.9 Disconnected mode (DM) response. 22
4 Elements for layer-to-layer communication .23
4.1 Definition of primitives and parameters. 23
4.1.1 Generic names . 23
4.1.1.1 DL-ESTABLISH. 23
4.1.1.2 DL-RELEASE. 23
4.1.1.3 DL-DATA. 23
4.1.1.4 DL-UNIT DATA . 23
4.1.1.5 DL-SUSPEND. 23
4.1.1.6 DL-RESUME. 23
4.1.1.7 DL-RECONNECT . 24
4.1.1.8 DL-RANDOM ACCESS. 24
4.1.1.9 MDL-RELEASE. 24
4.1.1.10 MDL-ERROR . 24
4.1.1.11 PH-DATA . 24
4.1.1.12 PH-RANDOM ACCESS . 24
4.1.1.13 PH-CONNECT . 24
4.1.1.14 PH-READY-TO-SEND . 24
4.1.1.15 PH-EMPTY-FRAME. 24
4.1.2 Primitives types. 24
4.1.2.1 REQUEST. 24
4.1.2.2 INDICATION . 25
4.1.2.3 RESPONSE . 25
4.1.2.4 CONFIRM . 25
4.1.3 Parameter definition. 25
4.1.3.1 Message unit. 25
4.1.3.2 Channel type . 26
4.1.3.3 Service Access Point . 26
4.1.3.4 Release mode. 26
4.1.3.5 Error cause . 26
4.1.3.6 Establish mode . 26
4.2 Primitive procedures .30
5 Definition of the peer-to-peer protocol LAPDm. 31
5.1 General. 31
5.2 General Protocol Procedures. 32
5.2.1 Unacknowledged information transfer. 32
5.2.2 Acknowledged multiple frame information transfer . 32
5.3 Procedures for unacknowledged information transfer . 32
5.3.1 General . 32
5.3.2 Transmission of unacknowledged information . 32
5.3.3 Receipt of unacknowledged information. 32
5.4 Procedures for establishment and release of multiple frame operation. 33
5.4.1 Establishment of multiple frame operation . 33
5.4.1.1 General . 33
5.4.1.2 Normal establishment procedures . 33
5.4.1.3 Procedure on expiry of timer T200: Normal establishment. 34
5.4.1.4 Contention resolution establishment procedure. 34
5.4.1.5 Procedure on expiry of timer T200: contention resolution
(MS only). 36
5.4.2 Information transfer . 36
5.4.2.1 General requirements . 36
5.4.2.2 Error conditions. 37
5.4.2.3 Fill frames . 37
5.4.3 Suspension and resumption of multiple frame operation . 38
5.4.3.1 General . 38
5.4.3.2 Suspension . 39
5.4.3.3 Resumption. 39
5.4.3.3.1 Procedure after channel change. 39
5.4.3.3.2 Procedure after returning to the old
channel (MS only) . 40
5.4.4 Termination of multiple frame operation. 40

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5.4.4.1 General.40
5.4.4.2 Normal release procedure.41
5.4.4.3 Procedure on expiry of timer T200 for normal release .41
5.4.4.4 Local end release procedure .41
5.4.5 Idle state.42
5.4.6 Collision of unnumbered commands and responses .42
5.4.6.1 Identical transmitted and received commands .42
5.4.6.2 Different transmitted and received commands.42
5.4.6.3 Unsolicited DM response and SABM or DISC command.42
5.5 Procedures for information transfer in multiple frame operation .43
5.5.1 Transmitting I frames .43
5.5.2 Receiving I frames.43
5.5.2.1 P bit of the received I frame set to "1" .44
5.5.2.2 P bit of the received I frame set to "0" .44
5.5.3 Receiving acknowledgement.44
5.5.3.1 On receipt of a valid I frame .44
5.5.3.2 Receiving supervisory command frames with the P bit set
to "1" .45
5.5.4 Receiving REJ frames.45
5.5.4.1 Receipt of a valid REJ frame.45
5.5.4.2 Transmitting frames.46
5.5.5 Receiving RNR frame.46
5.5.6 Data link layer own receiver busy condition .47
5.5.7 Waiting acknowledgement .48
5.6 Abnormal release and re-establishment of multiple frame operation .49
5.6.1 Criteria for re-establishment.49
5.6.2 Criteria for abnormal release.49
5.6.3 Procedures for re-establishment.49
5.6.4 Procedures for abnormal release.49
5.7 Exception condition reporting and recovery for multiple frame operation.49
5.7.1 N(S) sequence error.50
5.7.2 Timer recovery .50
5.7.3 Invalid frame condition .50
5.7.4 N(R) sequence error.51
5.8 List of system parameters.51
5.8.1 Timer T200.51
5.8.1.1 For SAPI=0 and SAPI=3.51
5.8.1.2 For SAPIs other than 0 or 3.51
5.8.2 Maximum number of retransmissions (N200).52
5.8.2.1 For SAPI=0 and 3 .52
5.8.2.2 For SAPIs other than 0 or 3.52
5.8.3 Maximum number of octets in an I, UI, SABM and UA frame information
field (N201).52
5.8.4 Maximum number of outstanding I frames (k) .52
5.8.5 Maximum number of octets in a Layer 3 message .52
5.9 System performance requirements .52
6 Special protocol operation on SAPI=0 and SAPI=3 .53
Annex A (normative): Random access procedures.55
A.1 Description of the procedure .55
A.1.1 Procedure in the MS .55
A.1.2 Procedure in the BS.55
A.2 Format.55
Annex G (normative): Handling of frames with parameter errors in the address, control and length
indicator fields.56
G.1 General.56
G.2 Parameter errors in the address field.56

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G.2.1 Unallocated SAPI . 56
G.2.2 Wrong value of the C/R bit. 56
G.2.3 EA bit set to "0" . 56
G.3 Parameter errors in the control field . 57
G.3.1 Supervisory frames . 57
G.3.2 Unnumbered frames . 57
G.4 Parameter errors in the length indicator field. 57
G.4.1 EL bit error. 57
G.4.2 Information frames . 57
G.4.3 Supervisory frames . 58
G.4.4 DISC and DM frames. 58
G.4.5 SABM UA and UI frames . 58
History. 59

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Foreword
This European Telecommunication Standard (ETS) has been produced by the Special Mobile Group
(SMG) Technical Committee (TC) of the European Telecommunications Standards Institute (ETSI).
This ETS defines the data link layer protocol of the Mobile Station - Base Station System (MS - BSS)
interface within the digital cellular telecommunications system.
The ETS from which this ETS has evolved is Phase 2 GSM ETS 300 555 (GSM 04.06 version 4.4.0).
The contents of this ETS is subject to continuing work within TC-SMG and may change following formal
TC-SMG approval. Should TC-SMG modify the contents of this ETS, it will be resubmitted for OAP by
ETSI with an identifying change of release date and an increase in version number as follows:
Version 5.x.y
where:
y the third digit is incremented when editorial only changes have been incorporated in the
specification;
x the second digit is incremented for all other types of changes, i.e. technical enhancements,
corrections, updates, etc.
The specification from which this ETS has been derived was originally based on CEPT documentation,
hence the presentation of this ETS may not be entirely in accordance with the ETSI drafting rules.
Annexes B to F were deleted from the original specification, however, for referencing purposes the annex
numbering has been maintained.
Transposition dates
Date of adoption: 28 March 1997
Date of latest announcement of this ETS (doa): 31 July 1997
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 January 1998
Date of withdrawal of any conflicting National Standard (dow): 31 January 1998

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0 Scope
This European Telecommunication Standard (ETS) defines a data link layer protocol to be used for
signalling, and possibly also for other applications, on the MS-BS interface.
0.1 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references, the
latest edition of the publication referred to applies.
[1] GSM 01.04 (ETR 350): "Digital cellular telecommunications system (Phase 2+);
Abbreviations and acronyms".
[2] GSM 04.01: "Digital cellular telecommunications system; Mobile Station - Base
Station System (MS - BSS) interface; General aspects and principles".
[3] GSM 04.03: "Digital cellular telecommunications system (Phase 2+); Mobile
Station - Base Station System (MS - BSS) interface Channel structures and
access capabilities".
[4] GSM 04.04 (ETS 300 936): "Digital cellular telecommunications system; Layer 1
General requirements".
[5] GSM 04.05 (ETS 300 937): "Digital cellular telecommunications system; Data
Link (DL) layer General aspects".
[6] GSM 04.07 (ETS 300 939): "Digital cellular telecommunications system
(Phase 2+); Mobile radio interface signalling layer 3; General aspects".
[7] GSM 04.08 (ETS 300 940): "Digital cellular telecommunications system
(Phase 2+); Mobile radio interface layer 3 specification".
[8] GSM 04.10 (ETS 300 941): "Digital cellular telecommunications system; Mobile
radio interface layer 3 Supplementary services specification; General aspects".
[9] GSM 04.12 (ETS 300 943): "Digital cellular telecommunications system
(Phase 2+); Short Message Service Cell Broadcast (SMSCB) support on the
mobile radio interface".
[10] GSM 05.02 (ETS 300 908): "Digital cellular telecommunications system
(Phase 2+); Multiplexing and multiple access on the radio path".
[11] GSM 08.56: "Digital cellular telecommunications system; Base Station Controller
- Base Transceiver Station (BSC - BTS) interface; Layer 2 specification".
[12] GSM 08.58: "Digital cellular telecommunications system (Phase 2+); Base
Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 3
specification".
[13] CCITT Recommendation Z.100: "Specification and description language (SDL)".
0.2 Abbreviations
Abbreviations used in this ETS are listed in GSM 01.04.

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1 General
This ETS describes the frame structure, elements of procedure, format of fields and procedures for the
proper operation of the Link Access Procedure on the Dm channel, LAPDm.
NOTE 1: The term Dm channel is used for convenience to designate the collection of all the
various signalling channels required in the GSM system. See also GSM 04.03.
The concepts, terminology, overview description of LAPDm functions and procedures, and the relationship
with other Technical Specifications are described in general terms in GSM 04.05.
The frame formats defined for LAPDm are based on those defined for LAPD. However, there are
important differences between LAPDm and LAPD, in particular with regard to frame delimitation methods
and transparency mechanisms. These differences are necessary for operation within the constraints set
by the radio path.
LAPDm supports two modes of operation:
- unacknowledged operation using UI frames;
- acknowledged operation using the multiple frame procedure.
As a choice of implementation, the two modes of operation may be implemented independently of each
other. This is possible since there is no interactions between the two modes, other than queuing at the
transmitter, even when they coexist on the same physical channel. For BCCHs and CCCHs only the
unacknowledged mode of operation needs to be implemented.
LAPDm is used for information sent on the control channels BCCH, AGCH, PCH, FACCH, SACCH and
SDCCH as defined in GSM 04.03.
NOTE 2: AGCH and PCH are sometimes referred to by the collective name CCCH and FACCH,
SACCH and SDCCH are, similarly, referred to by the collective name DCCH.
LAPDm may also be used on other types of channel.
NOTE 3: As stated in GSM 04.05, the term "data link layer" is used in the main text of this ETS.
However, mainly in figures and tables, the terms "layer 2" and "L2" are used as
abbreviations. Furthermore, in accordance with GSM 04.07 and GSM 04.08, the term
"layer 3" is used to indicate the layer above the data link layer.
This ETS is organized as follows:
The frame structure for peer-to-peer communication is given in clause 2. The elements of procedure and
formats of fields are given in clause 3. The elements of layer-to-layer communication are contained in
clause 4. The details of the peer-to-peer procedures are given in clause 5. Clause 6 summarizes the
special protocol operations used mandatorily with SAPI=0 and SAPI=3.
The specification for the random access channel is contained in annex A, even though it is not a LAPDm
function. This part of the ETS is descriptive and does not constrain t
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