3GPP 24.501 v20.0.0 — the document's own text
5.1.1 General
Taught in 1. What CT1 is, and the three names it answers to (CT1 — the group that writes what your phone says, in depth), 4. TS 24.501 — two protocols living in one document (CT1 — the group that writes what your phone says, in depth), 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The main function of the 5GS mobility management (5GMM) sublayer is to support the identification, security, mobility of a UE as well as generic message transport.
A further function of the 5GMM sublayer is to provide connection management services to the other sublayer(s).
NOTE: In a satellite NG-RAN access, a GNSS fix time in lower layers can delay transmission of an initial UL NAS message by up to 100 seconds (GNSS cold state).