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Network identities assigned to a mobile device can be native or mapped ones.

 Native Identity

A network element may construct a native identity from several fundamental identities. A network element may allocate a native identity to another network element for its identification and tracking of various resources allocated to it. An example of native identity in the case of LTE/EPS is the GUTI as shown in Example 5.2; in Figure 5.3. MME assigns a GUTI to a UE and is used during the various EPS mobility management layer procedures. Similarly, in the GPRS system, the SGSN allocates a P‐TMSI to an MS.

 Mapped Identity

A mapped identity is derived from a certain portion of a native identity or may assign the whole native identity. One example of mapped identity is the NRI used in a GPRS system that is derived either from a TMSI or P‐TMSI. Similarly, a TLLI, which is used in the GPRS system, is derived from a P‐TMSI, as shown in Example 5.4 and Figure 5.5.

 Mapped identity due to intersystem changes

An LTE E‐UTRAN UE may support multiple RATs to provide communication services through legacy networks. Such a UE registers with the legacy CNs also where the respective network identities are allocated to the UE to provide seamless communication service to the user. During the intersystem changes from E‐UTRAN/LTE/EPS to GERAN/UTRAN (UMTS) and vice versa due to its mobility, a UE identity shall be mapped into another identity, as shown in Example 5.5 and Figure 5.6.