BSC support for "network sharing" via MOCN
This allows for RAN sharing between operators.It includes
- transmitting some new SI types on the BCCH (mainly SI22, optionally SI23 and SI21) to broadcast up to four additional PLMNs.
- some additional signaling to select different operators' MSCs in the BSC in MOCN
- some additional functionalty in a MSC if the MSC is shared in GWCN
Relevant top-level spec: TS 23.251
See also Interesting3GPPSpecsForDevelopers
The required functionality can be summarized as:
- A interface connections to multiple MSCs (already required for e.g. MSC pooling as per #3682)
- actually, each operator can have a MSC pool, so we have two dimensions of 'multiple connections'
- generation of additional SYSTEM INFORMATION messages(SI22, SI23, SI21)
- SI22 is the only mandatory part. SI23 is very complex and contains inter-RAT handover paramters for secondary PLNNs. SI21 contains access barring for them.
- transmit them over Abis to BTSs
- routing of MOCN-supported UEs initial access to respective operator ("PLMN index" in INITIAL L3 MESSSAGE)
- routing of MOCN-unsupported UEs initial access to one operator
- setting the "redirect attempt" flag in related messages to MSC
- handle subsequent re-direction to other CN to other operotors
- transmit PLMN-id of current core operator in SYSTEM INFORMATION on SACCH
- handover needs to include PLMN identity in related messages