Can someone educate me on this TCSM (Transcoder / Sub multiplexer)?

Question

Actually i tried to Google this but didn't get the clear definitions of these terms. Some NSN documents i got but that were not to learn from.
I am expecting that i will get the simple definitions of these terms and what is their role in GSM, where do they placed in network. What's the benefit.

Thanks in advance.

Answer 1

Transcoders and sub-multiplexers

are used between the BSC and MSC. Although they are present in the BSS system but physically they may be situated at the MSC location.

The TCSM is capable of two functions: Transcoding of speech signals and sub-multiplexing of PCM signals.

The Transcoder does the speech coding in the downlink direction, which decoded in the MS, and it decodes the speech signal in the uplink direction.

Sub-multiplexers are located at the same place as the transcoders and are responsible for multiplexing of the PCM links between BSC and MSC.