LAPDm

Asynchronous Transfer Mode

*LDPDmWhat is Lapdm ? Link Access Protocol on D-channel LAPDm is a data link layer protocol used in GSM cellular networks. LAPDm forms Layer 2 of the Um interface between the Base Transceiver Station and Mobile station.LAPDm is derived from a much older link layer protocol called HDLC and specified in 3GPP specifications TS 04.05 and 04.06.LAPDm is similar to the ISDN Layer 2

Lapdm SpecificationLAPDm frames are always 184 bits, with segmentation for larger messages.LAPDm does not support extended header formats.LAPDm has just one internal timer, T200.LAPDm supports only one terminal endpoint, whose TEI is implied.LAPDm supports only two SAPs: SAP3 for SMS and SAP0 for everything else.

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