UE IDENTIFIERS IN LTE

Below are some important UE identifiers used in LTE.

 

Cell Radio Network Temporary Identifier (C-RNTI)

The Cell Radio Network Temporary Identifier (C-RNTI) is used over the LTE air interface.

-Uniquely identifies the UE within a certain cell.
-Exists only when the UE is in the ECM-CONNECTED state.
-Allocated by eNodeB

Temporary Mobile Subscriber Identity (S-TMSI)

-Uniquely identifies the UE within a certain tracking area.
-Used over air interface when the UE is in the ECM-IDLE state.
-Allocated by MME

Globally Unique Temporary Identity (GUTI)

-Considered an extended version of the S-TMSI
-Uniquely identifies both the UE within a certain tracking area and the MME handling the UE.

International Mobile Subscriber Identity (IMSI)

-Uniquely identifies the UE anywhere in the world
-Used carefully over air interface. Not transmitted unencrypted over the air interface if not absolutely necessary
-Allocated by home Network operator

International Mobile Equipment Identity (IMEI)

Uniquely identifies the teminal equipment hardware globally.
This number can be used by the network to stop a stolen phone from accessing the network.