Content for  TS 44.006  Word version:  16.0.0

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1  ScopeWord‑p. 8

The present document defines a data link layer protocol to be used for signalling, and possibly also for other applications, on the MS BS interface.

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.
TR 21.905: "Vocabulary for 3GPP Specifications".
TS 44.001: "Mobile Station - Base Station System (MS - BSS) Interface General Aspects and Principles".
TS 44.003: "Mobile Station - Base Station System (MS - BSS) interface Channel structures and access capabilities".
TS 44.004: "Layer 1 General requirements".
TS 44.005: "Data Link (DL) layer General aspects".
TS 24.007: "Mobile radio interface signalling layer 3; General aspects".
TS 44.018: "Mobile radio interface layer 3 specification; Radio Resource Control Protocol".
TS 24.010: "Mobile radio interface layer 3 Supplementary services specification; General aspects".
TS 44.012: "Short Message Service Cell Broadcast (SMSCB) support on the mobile radio interface".
TS 45.002: "Multiplexing and multiple access on the radio path".
TS 48.056: "Base Station Controller Base Transceiver Station (BSC BTS) interface; Layer 2 specification".
TS 48.058: "Base Station Controller Base Transceiver Station (BSC BTS) interface; Layer 3 specification".
CCITT Recommendation Z.100: "Specification and description language (SDL)".

3  Abbreviations

Abbreviations used in the present document are listed in TS 21.905.

4  GeneralWord‑p. 9

The present document 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.
The concepts, terminology, overview description of LAPDm functions and procedures, and the relationship with other Technical Specifications are described in general terms in TS 44.005.
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, NCH, PCH, FACCH, SACCH and SDCCH as defined in TS 44.003.
LAPDm may also be used on other types of channel.
This Technical Specification is organized as follows:
The frame structure for peer to peer communication is given in clause 5. The elements of procedure and formats of fields are given in clause 6. The elements of layer to layer communication are contained in clause 7. The details of the peer to peer procedures are given in clause 8. 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. The present document is descriptive and does not constrain the implementation of the random access function. The procedure is used for CHANNEL REQUEST on the RACH and HANDOVER ACCESS on the main DCCH.
(Annexes B to F are deleted).
Annex G gives an overview of actions taken on frames containing parameter errors.

4.1  Options

Support of short L2 header type 1 is an option in both the mobile station and the network; under certain conditions the support is mandatory, as specified in other Specifications. A layer 2 protocol entity not implementing short L2 header type 1 shall diagnose an E/A bit error and proceed as defined in clause G.2.3.

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