Base Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 1 structure of physical circuits
The use and general aspects of the A-bis interface are given in 3GPP TS 48.051.
The present document defines the structure of the physical layer (layer 1) of the BSC - BTS/TRX interface for supporting traffic channels and control channels. Use of the physical layer for supporting link protocol is covered in 3GPP TS 48.056.
The physical layer is the lowest layer in the OSI Reference Model and it supports all functions required for transmission of bit streams on the physical medium.