Identifiers used in LTE.

These are the identifiers used in LTE technology.

Identifiers Full Form Description Length of Identifiers
IMSI International Mobile Subscriber Identity Unique identification of mobile (LTE) subscriber Network (MME) gets the PLMN of the subscriber IMSI (not more than 15 digits) = PLMN ID + MSIN = MCC + MNC + MSIN
PLMN ID Public Land Mobile Network Identifier Unique identification of PLMN PLMN ID (not more than 6 digits) = MCC + MNC
MCC Mobile Country Code assigned by ITU 3 digits
MNC Mobile Network Code assigned by National Authority 2 or 3 digits
MSIN Mobile Subscriber Identification Number assigned by operator 9 or 10 digits
GUTI Globally Unique Temporary UE Identity To identify a UE between the UE and the MME on behalf of IMSI for security reason GUTI (not more than 80 bits) = GUMMEI + M-TMSI
TIN Temporary Identity used in Next Update GUTI is stored in TIN parameter of UE’s MM context. TIN indicates which temporary ID will be used in the next update. TIN = GUTI
S-TMSI SAE Temporary Mobile Subscriber Identity To locally identify a UE in short within a MME group (Unique within a MME Pool) S-TMSI (40 bits) = MMEC + M-TMSI
M-TMSI MME Mobile Subscriber Identity Unique within a MME 32 bits
GUMMEI Globally Unique MME Identity To identify a MME uniquely in globalGUTI contains GUMMEI GUMMEI (not more than 48 bits)= PLMN ID + MMEI
MMEI MME Identifier To identify a MME uniquely within a PLMNOperator commissions at eNBMMEI MMEI (24 bits) = MMEGI + MMEC
MMEGI MME Group Identifier Unique within a PLMN 16 bits
MMEC MME Code To identify a MME uniquely within a MME Group. S-TMSI contains MMEC8 8 bits
C-RNTI Cell- Radio Network Temporary Identifier To identify an UE uniquely in a cell 0x0001 ~ 0xFFF3 (16 bits)
IMEI International Mobile Equipment Identity To identify a ME (Mobile Equipment) uniquely IMEI (15 digits) = TAC + SNR + CD
IMEI/SV IMEI/Software Version To identify a ME (Mobile Equipment) uniquely IMEI/SV (16 digits) = TAC + SNR + SVN
ECGI E-UTRAN Cell Global Identifier To identify a Cell in global (Globally Unique)EPC can know UE location based of ECGI ECGI (not more than 52 bits) = PLMN I D+ ECI
ECI E-UTRAN Cell Identifier To identify a Cell within a PLMN ECI (28 Bits) = eNB ID + Cell ID
PGW ID PDN GW Identity To identify a specific PDN GW (P-GW)HSS assigns P-GW for PDN (IP network) connection of each UE IP address (4 bytes) or FQDN (variable length)
TAI Tracking Area Identity To identify Tracking AreaGlobally uniqueTAI TAI (not more than 32 bits) = PLMN ID + TAC P-GW
TAC Tracking Area Code To indicate eNB to which Tracking Area the eNB belongs (per Cell)Unique within a PLMN16 16 bits
TAI List Tracking Area Identity List UE can move into the cells included in TAL list without location update (TA update)Globally unique Variable length
PDN ID Packet Data Network Identity To identify an PDN (IP network), that mobile data user wants to communicate withPDN Identity (APN) is used to determine the P-GW and point of interconnection with a PDN

With APN as query parameter to the DNS procedures, the MME will receive a list of candidate P-GWs, and then a P-GW is selected by MME with policy

PDN Identify = APN = APN.NI + APN.OI (variable length)
EPS Bearer ID Evolved Packet System Bearer Identifier To identify an EPS bearer (Default or Dedicated) per an UE4 4 bits
E-RAB ID E-UTRAN Radio Access Bearer Identifier• To identify an E-RAB per an UE 4 bits
DRB ID Data Radio Bearer Identifier To identify a DRB per an UE4 4 bits
LBI Linked EPS Bearer ID To identify the default bearer associated with a dedicated EPS bearer4 4 bits
TEID Tunnel End Point identifier To identify the end point of a GTP tunnel when the tunnel is established 32 bits


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