What are the interfaces between the BSS and MSC&&TRAU and BSC?

BSS and MSC:

- BSS will send the called number to MSC(Mobile Switching Center)
- MSC checks the VLR and queries BSS for allocation of resources for the cell
- Then MSC routes the call to GMSC
- Switching nodes for base station controls is done by MSC

b.) TRAU and BSC:

- TRAU (Transcoder and Rate Adaptation Unit) is an entity to perform a transcoding function for speech channels and RA(Rate Adaptation) for various data channels.
- BSC and TRAU does not demand specific environmental conditions to perform operations.
- With this the operator has an option for placing any one or both units at a central location.
- BSC supports various BSC-BTS configurations like star, multidrop and loop, and star configurations towards TRAU
- TRAU is a stand alone unit which could be located close to a MSC(Mobile Switching Center), which enables the optimum utilization of 16 kbit/s channel sub multiplexing and saves line costs.