I am assuming here that question is related to UE identifiers.
An UE is identified using the various identifiers at nodes of lte network.
Protocol Identifiers
EnodeB S1AP layer MME-UE-S1AP-ID, ENODEB-UE-S1AP-ID
EnodeB RRC local to vendor specific
EnodeB MAC C-RNTI, P-RNTI etc.
MME NAS GUTI, IMSI
GTP IMSI, C-TEID
PGW IMSI, IP address