ETSI TS 148 056 V13.0.0 (2016-01)

ETSI TS 1148 056 V13.0.0 (201616-01)






TECHNICAL SPECIFICATIONION
Digital cellular telecocommunications system (Phahase 2+);
Base Station Controller r - Base Transceiver Station (n (BSC - BTS)
interface;
Layayer 2 specification
(3GPP TS 48.0.056 version 13.0.0 Release 13 13)

R
GLOBAL SYSTTEME FOR
MOBILE COMMUUNNICATIONS

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3GPP TS 48.056 version 13.0.0 Release 13 1 ETSI TS 148 056 V13.0.0 (2016-01)



Reference
RTS/TSGG-0248056vd00
Keywords
GSM
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3GPP TS 48.056 version 13.0.0 Release 13 2 ETSI TS 148 056 V13.0.0 (2016-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI

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3GPP TS 48.056 version 13.0.0 Release 13 3 ETSI TS 148 056 V13.0.0 (2016-01)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 4
1 Scope . 5
2 References . 5
3 Definitions and abbreviations . 6
4 General description. 6
5 Functional contents . 7
6 LAPD functions . 7
6.1 Exceptions and modifications. 7
6.1.1 Void . 7
6.1.2 Command/Response field bit (C/R) . 7
6.1.3 Service Access Point Identifier (SAPI) . 7
6.1.4 TEI for point-to-point data link connection . 8
6.1.5 Commands and responses . 8
6.1.6 Exchange identification (XID) command/response . 8
6.1.7 MDL-XID . 8
6.1.8 PH-DATA, PH DEACTIVATE and PH-ACTIVATE . 8
6.1.9 MPH-ACTIVATE, MPH-DEACTIVATE an MPH-INFORMATION . 8
6.1.10 Priority indicator . 9
6.1.11 Terminal Endpoint Identifier (TEI) management procedures . 9
6.1.11.1 General . 9
6.1.11.2 TEI assignment procedure . 9
6.1.11.3 TEI identity verify procedure . 11
6.1.11.4 Formats and codes. . 11
6.1.12 Automatic negotiation of data link layer parameters . 11
6.1.13 Establishment procedures . 11
6.1.14 N(S) sequence error . 11
6.1.15 List of system parameters . 11
6.1.15.1 Timer T200 . 12
6.1.15.2 Maximum number of retransmissions (N200) . 12
6.1.15.3 Maximum number of octets in an information field (N201) . 12
6.1.15.4 Maximum number of transmission of the TEI identity request message (N202) . 12
6.1.15.5 Maximum number of outstanding frames (K) . 12
6.1.15.6 Timer T201 . 12
6.1.15.7 Timer T202 . 12
6.1.15.8 Timer T203 . 12
6.1.16 Data link layer monitor function . 13
6.1.17 Miscellaneous . 13
Annex A (informative): Change History . 14
History . 15

ETSI

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3GPP TS 48.056 version 13.0.0 Release 13 4 ETSI TS 148 056 V13.0.0 (2016-01)
Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.

ETSI

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3GPP TS 48.056 version 13.0.0 Release 13 5 ETSI TS 148 056 V13.0.0 (2016-01)
1 Scope
The present document specifies the link layer used for signalling on the A-bis interface between BSC and BTS. The use
and general aspects of the A-bis interface are described in 3GPP TS 48.051 and the interface aspects in 3GPP TS
48.052.
The Link Access Procedure on the D-channel (LAPD) specification used on the A-bis interface in the GSM PLMN is a
subset of the EN 300 125 which in turn has less options than the CCITT Recommendation Q.921.
This description contains first the protocol definitions and second the services provided by the layer 2 to the layer 3.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TS 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 48.051: "Base Station Controller - Base Transceiver Station (BSC - BTS) interface;
General aspects".
[3] 3GPP TS 48.052: "Base Station Controller - Base Transceiver Station (BSC - BTS) interface;
Interface principles".
[4] Void.
[5] Void.
[6] Void.
[7] Void.
[8] Void.
[9] Void.
[10] Void.
[11] Void.
[12] Void.
[13] Void.
[14] Void.
[15] Void.
[16] Void.
[17] Void.
[18] Void.
ETSI

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3GPP TS 48.056 version 13.0.0 Release 13 6 ETSI TS 148 056 V13.0.0 (2016-01)
[19] CCITT Recommendation Q.921: "Integrated services digital network (ISDN) user-network
interface - Data link layer specification".
[20] EN 300 125: "Integrated Services Digital Network (ISDN); User-network interface data link layer
specification Application of CCITT Recommendations Q.920/I.440 and Q.921/I.441".
3 Definitions and abbreviations
Abbreviations used in the present document are listed in 3GPP TS 21.905.
4 General description
The following information categories are supported by the procedures of this layer 2 Recommendation:
- signalling (including Short Message Service (SMS) information);
- operation and maintenance;
- layer 2 management.
For each of these categories the BSC may have one or more layer 2 links to every TRX and BCF.
The signalling links over the A-bis interface are addressed to the different units by Terminal Endpoint Identifiers (TEI).
The same unit will normally have more than one functional entity. The logical links between different functional
entities are identified by functional addresses, the Service Access Points Identifier (SAPI).
Figure 1 shows the architectural model with different layer 2 links.
A number of logical links may be multiplexed on each physical link. The same layer 2 logical link may not be
distributed over more than one physical link.
____________________
| ________     |
| |    |     |
| |    | __   |            __  ______
| |    || |_______RSL________SAPI_=_0___| |__|   |
| |    || |_______OML________SAPI_=_62__| |__|   |
| |    || |_______L2ML_______SAPI_=_63__| |__| TRX |TEI 1
| |    || |               | |__|   |
| |    ||__|               |__| |______|
| |LAYER 2|     |            __  ______
| |    | __   |            | |__|   |
| |    || |_____|_RSL________SAPI_=_0___| |__|   |
| |    || |_______OML________SAPI_=_62__| |__| TRX |TEI 2
| |    || |_______L2ML_______SAPI_=_63__| |__|   |
| | T E I || |               | | |______|
| |    || |_______RSL________SAPI_=_0___| |  ______
| |    || |_______OML________SA
...