6 Interface characteristics

3GPP48.051Base Station Controller - Base Transceiver Station (BSC - BTS) interfaceGeneral AspectsRelease 17TS

The interface is defined to be at the terrestrial link of a remote BTS connected to the BSC.

The BSC to BTS interface is specified by a set of characteristics, including:

a) physical and electrical parameters;

b) channel structures;

c) signalling transfer procedures;

d) configuration and control procedures;

e) operation and maintenance information support.

The definition of the BSC to BTS/TRX interface follows a layered approach similar to the ISDN. Layer 3 is for the most part based on Technical Specification 3GPP TS 48.008 with additional procedures for control of radio resources. Layer 2 is based on the LAPD protocol. Layer 1 is either digital (at a rate 2 048 kbit/s with a frame structure of 32 x 64 kbit/s time slots or at a rate of 64 kbit/s) or analogue with the data being passed by the use of modems (this latter case is a national option).

In the case that the transcoder is positioned outside the BTS, the overall one way propagation delay between the Point of Interconnection to PSTN/ISDN and the MS is limited to 1,5 ms (approximately 300 km). With the transcoder in the BTS, the limit is 6,5 ms (approximately 1 300 km). These limits may be subject to increase resulting from savings made in the overall network. See also Technical Specification 3GPP TS 43.050.