The present document defines the service offered by the physical layer (3GPP TS 05-series of Technical Specifications) of the MS-BS interface (3GPP TS 05- and 04-series of Technical Specifications). Its main objective is to be a guidance for the interface between the 3GPP Technical Specifications in the 05-series and the 04-series. It also specifies the format of signalling channels and the order of bit transmission.

As far as possible, the present document makes use of the layering principles of the Reference Model for Open System Interconnection (OSI) as contained in ITU-T Recommendations X.200 and X.210.