This TS 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 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.
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 TS 04.03.