What are 4G S-TMSI and 5G S-TMSI, and how can you trace and check them? Also, in the realm of signaling analysis and optimization work, when might you need this data, and what are its use cases?
– 4G S-TMSI, and is part of GUTI, it is used to identify a UE within a specific MME Pool. It is included in RRCSetupRequest, Paging, and Initial UE Message. Where 4G S-TMSI is a combination of MME Code + M-TMSI.
– 5G S-TMSI can be used to identify a UE within a specific AMF Region. It is included in RRCSetupRequest, Paging, Registration request, and Initial UE Message. Where 5G S-TMSI is a combination of AMF Set Pointer, AMF Pointer + 5G-TMSI.
– In network troubleshooting, if a degradation is linked to a specific user, promptly gather TMSI information from live traces. Communicate this data to the Core team, enabling them to provide the corresponding IMSI for continued troubleshooting.
