GUTI (Globally Unique Temporary UE Identity)
3GPP TS 23.003 V9.3.0 (2010-06)
The format and size of the GUTI is therefore the following:
<GUTI> = <GUMMEI><M-TMSI>,
where <GUMMEI> = <MCC><MNC><MME Identifier>
and <MME Identifier> = <MME Group ID><MME Code>
MCC and MNC shall have the same field size as in earlier 3GPP systems.
M-TMSI shall be of 32 bits length.
MME Group ID shall be of 16 bits length.
MME Code shall be of 8 bits length.