04.053GPPData Link (DL) Layer General AspectsRelease 1999TS
The present document describes in general terms the Link Access Procedures on the Dm channel, LAPDm. The application of this protocol to other channel types is for further study. Details are provided in 3GPP TS 04.06.
The purpose of LAPDm is to convey information between layer 3 entities across the GSM PLMN radio interface (MS to network interface) using the Dm channel.
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 3GPP TS 04.03.
The definition of LAPDm is based on the principles and terminology of:
‑ CCITT Recommendations X.200 and X.210: the reference model for Open Systems Interconnection (OSI);
‑ CCITT Recommendations Q.920 and Q.921: the specification of LAPD for the user‑network interface in ISDN;
‑ CCITT Recommendation X.25 LAPB: user‑network interface for packet mode terminals; and
‑ ISO 3309 and ISO 4335: High‑level Data Link Control (HDLC) standards for frame structure and elements of procedures.
LAPDm is a protocol that operates at the data link layer of the OSI architecture. The relationship between the data link layer and other protocol layers is defined below.
NOTE 2: The interface between the mobile station and external terminal equipment/terminal adapters is defined in the Technical Specifications of the 3GPP TS 07‑series.
NOTE 3: The physical layer on the radio interface is defined in 3GPP TS 04.04 and layer 3 is defined in 3GPP TS 04.07, 04.08, 04.10 and 04.11. Reference should be made to these Technical Specifications for the complete definitions of the protocols and procedures across the GSM PLMN radio interface.
NOTE 4: The term "data link layer" is used in the main text of the present document. However, mainly in figures and tables, the terms "layer 2" and "L2" are used abbreviations. Furthermore, in accordance with 3GPP TS 04.07 and 04.08 the term "layer 3" is used to indicate the layer above the data link layer.
LAPDm is independent of the transmission bit rate. It requires physical channels with characteristics as defined in 3GPP TS 04.03.
Section 2 below describes basic concepts used in the present document and 3GPP TS 04.06.
Section 3 gives an overview description of LAPDm functions and procedures.
Section 4 summarizes the services that the data link layer provides to layer 3 and the services that the data link layer requires from the physical layer.
Section 5 provides an overview of the data link layer structure.
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.
 3GPP TS 01.04: "Abbreviations and acronyms".
 3GPP TS 04.01: "Mobile Station ‑ Base Station System (MS ‑ BSS) interface: General aspects and principles".
 3GPP TS 04.03: "Mobile Station ‑ Base Station System (MS ‑ BSS) interface: Channel structures and access capabilities".
 3GPP TS 04.04: "Layer 1: General requirements".
 3GPP TS 04.06: "Mobile Station ‑ Base Station System (MS ‑ BSS) interface: Data Link (DL) layer specification".
 3GPP TS 04.07: "Mobile radio interface signalling layer 3; General aspects".
 3GPP TS 04.08: "Mobile radio interface layer 3: specification".
 3GPP TS 04.10: "Mobile radio interface layer 3: Supplementary services specification General aspects".
 3GPP TS 04.11: "Point‑to‑Point (PP) Short Message Service (SMS) support on mobile radio interface".
 CCITT Recommendation X.25: "Interface between data terminal equipment (DTE) and data circuit ‑ terminating equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit".
 CCITT Recommendation X.200: "Reference Model of Open Systems Interconnection for CCITT Applications".
 CCITT Recommendation X.210: "Open Systems Interconnection layer service definition conventions".
 CCITT Recommendation Q.920: "Integrated services digital network (ISDN) user‑network interface ‑ Data link layer General aspects".
 CCITT Recommendation Q.921: "Integrated services digital network (ISDN) user‑network interface ‑ Data link layer specification".
 ISO 3309: "Information technology ‑ Telecommunications and information exchange between systems ‑ High level data link control (HDLC) procedures ‑ Frame structure".
 ISO/IEC 4335: "Information technology ‑ Telecommunications and information exchange between systems ‑ High level data link control (HDLC) procedures ‑ Elements of procedures".
Abbreviations used in the present document are listed in 3GPP TS 01.04.