1. CM Service Request
3. Set up message
4. MSC checking VLR profile
assignment request to the corresponding BSC to allocate a TCH for the call (CIC- Circuit
5. Send Routing Information (SRI)
profile and extracts current VLR/MSC.
6. Provide Roaming Number (PRN)
7. MSC2 will allocate an MSRN number from its MSRN pool to the IMSI of MS2.
8. PRN response
9. SRI response
10. Initial Address Message
that number. After resolving the routing path MSC1 will be instructed to communicate with
MSC2. IAM contains MSRN, Called party number, CIC.
11. After receiving the IAM message MSC2 will execute following,
- Check the MSRN table and resolve IMSI for MS2
- Check MS2 VLR profile
- Resolve MS2 s LAC and check the LAC table
- Resolve the BSCs inside that LAC
12. As requested from MSC2, paging is done in all the BSCs inside that LAC using the
TMSI of MS2
13. Paging response
15. Alert setup
16. MSC2 will send an assignment request to the BSC of MS2. Therefore a CIC is
allocated to proceed with the call.
17. Address Complete Message
20. Answer Message