TRAU(Transcoder/Rate Adaptation Unit)

Transcoder

The Transcoder/Rate Adaptation Unit (TRAU) is the data rate conversion unit. The PSTN/ISDN switch is a switch for 64kbps voice. Current technology permits to decrease the bit-rate (in GSM radio interface it is 13 kbps for full rate and 6.5 kbps for half rate). Since MSC is basically a PSTN/ISDN switch its bit-rate is still 64 kbps. That is why a rate conversion is required in between the BSC and MSC (see the figure below).

3.2 Base Station Controller

A Base Station Controller (BSC) is a high-capacity switch with radio communication and mobility control capabilities. The

functions of a BSC include radio channel allocation, location update, handover, timing advance, power control and paging.

There are more on this later.