GUTI -Globally Unique Temporary Identifier
AMF is in-charge to assign GUTI to an UE and it is common to
both 3GPP and non-3GPP access.
5G GUTI (80 bits) = GUAMI + 5G TMSI
GUAMI - Globally Unique AMF
Identifier
AMF Region ID: identifies the region
AMF Set ID: identifies the AMF Set
within the AMF Region
AMF Pointer: identifies the AMF
within the AMF Set.
GUAMI = AMF Region ID + AMF Set ID + AMF Pointer ID
TMSI identifies the UE with in the
AMF
Since GUTI is longer, to enable more efficient radio resources (especially in
Paging and Service Request), new identifier called 5G-S-TMSI is created.
S-TMSI (48 bits)= AMF Set ID + AMF Pointer ID + 5G TMSI