Rftechpoint

To visualize protocols interaction for UE Registration Request.

NAS Layer (TS 24.501): Generates the Registration Request.

RRC Layer (TS 38.331): Wraps the NAS PDU into an RRCSetupComplete and sends it over the SRB1 (Signaling Radio Bearer 1).

NGAP Layer (TS 38.413): The gNB receives it, strips the RRC headers, and wraps the NAS PDU into an Initial UE Message for the AMF.

🚀 Why is the User Location Information (ULI) in the Initial UE Message so critical?

It’s not just for paging! 👀👀

The gNB makes the first choice of AMF, but the ULI (TAI/Cell ID) allows the NSSF to perform a final audit. If the location data shows the current AMF doesn't support the requested slice in that specific zone, the ULI triggers AMF Reselection (AMF Re-allocation). No ULI = No accurate slicing validation!

Easy but important for right view of IE (Information Element).