Mainly the purpose of signaling can be divided to three groups
• speech and data connection (to set up, supervise, and release a call)
• mobility management (location update, handover)
• Subscriber administration (including all basic and supplementary GSM services
Now for covering these tasks generally two formats of signaling exist
1. Circuit-related (consist of CIC)
2. Non-circuit-related ( No CIC) MM uses this format.
For Location Update procedure BSC works as transparently so when MSC wants to speak with MS uses first BSSAP – DTAP in which information related to LU and Call setup are carried.
One sample of MM is LU, this happens when LAC of cell is different from MS’s LAC which it is saved on SIM card, then LU procedure starts …
MM-LU in POOL MSC is a bit different, because you don’t need to do LU between VLR so you reduce signaling between BSS and MSC , it is a good effect of MSC in pool.
Hope they come in use for u