Two of the identities from UMTS/GSM world are still used in LTE world
1. IMSI which uniquely identifies the subscriber or specifically SIM card. IMSI consists of MCC+MNC+MSIN
2.IMEI which identifies the device. IMEI has a TAC which identifies the device manufacturer and a SN which identifies the device.It may have a version number too
In addition to that the main identities are
1.GUTI :- Similar to TMSI in UMTS, GUTI-Global Unique Temporary Identifier is a temporary identifiier.GUTI will be allocated during attach procedure and will be used for identifying the UE thereafter
GUTI consists of MCC+MNC+MMEID(MME-GROUP & MME-Code)+M-TMSI
MME-Code and M-TMSI together is called S-TMSI and is used in paging.
2.Radio Network Temporary Identifiers (RNTIs) : RNTIs are similar to the ones in HSPA. Since shared channels are used for data transfer in LTE, we need some identifier to say this data belongs to this particular UE. RNTIs are for that purpose.
Various RNTIs are present,
C-RNTI:-
RA-RNTI :- RA response will contain the RA-RNTI
P-RNTI :- To a group of UEs, derived from the IMSI
SI-RNTI:- Indicates which resource blocks carry SIBs.
3.TAI: Identifies Tracking Area; A tracking area is a collection of one or more E-UTRAN cells. How they are mapped depends on proprietery radio planning. One cell can be part of multiple TAs as well. Paging happens at TA level
4.E-UTRAN CGI- Cell Global Identity consists of PLMN id (MCC+MNC) and CI (Cell Id is a 28 bit string, leftmost bits uniquely identify eNodeb) Thus CGI uniquely identifies the E-UTRAN cell.
