Intra-domain connection of OsmoBSC to multiple MSCs
3GPP TS 23.236 specifies the "Intra-domain connection of
Radio Access Network (RAN nodes to multiple Core Network (CN) nodes".
- a deviation from the strict hierarchy of classic GSM architecture where a BSC is always only served by one MSC
- the introduction of "MSC pools" where a pool of multiple MSCs cover one geographic service area.
This appears to be functioning by dividing the TMSI range between different MSCs, using the higher-order TMSI bits to identify the MSC and the lower-order TMSI bits for the actual TMSI within that MSC.
Section 5.3 describes the functions required to be implemented in the BSC.
- splitting of TMSI allocation range/spce
- storing of Global-CN-ID when receiving paging from MSC; routing paging response to that Global-CN-ID
- VTY configuration of number of TMSI bits reserved for NRI
- VTY configuration of NRI <-> MSC SCCP address mappings