4.3.19 Core Network node resolution

23.4013GPPGeneral Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) accessRelease 18TS

4.3.19.1 General

The indication of mapped or native GUTI shall be signalled by the UE to the MME as an explicit indication in Attach Request and TAU Request messages. The indication of mapped or native P-TMSI/RAI shall be signalled by the UE to the SGSN as an explicit indication in Attach Request and RAU Request messages. The MME/SGSN resolves the old MME/SGSN using old GUTI respective old P-TMSI/RAI sent in the Attach request and TAU/RAU request messages, and determines if the old GUTI or the old P-TMSI/RAI is mapped or native by one of the following two methods:

– Indication using most significant bit (MSB) in LAC and MME Group ID.

– Explicit indication sent from UE to MME and SGSN.

4.3.19.2 MSB in LAC and MME Group ID

For PLMNs deployed with such mechanism the MME differentiates between a GUMMEI mapped from P-TMSI/RAI and a native GUMMEI based on the value of most significant bit of the MME Group ID; i.e. the MSB is set to "0" then the GUMMEI is mapped from P-TMSI/RAI and if MSB is set to "1", the GUMMEI is a native one, as specified in TS 23.003 [9].

For PLMNs deployed with such mechanism the S4-SGSN differentiates between a P-TMSI/RAI mapped from GUTI and a native P-TMSI/RAI based on the value of most significant bit of the LAC; i.e. the MSB is set to "1" then the P‑TMSI/RAI is mapped from GUTI and if MSB is set to "0", the P-TMSI/RAI is a native one, as specified in TS 23.003 [9].

4.3.19.3 Explicit Indication

For PLMNs deployed with such mechanism the MME differentiates between a GUTI mapped from P-TMSI/RAI or a native GUTI based on the explicit indication sent by the UE.

For PLMNs deployed with such mechanism the S4-SGSN differentiates between a P-TMSI/RAI mapped from GUTI or a native P-TMSI/RAI based on the explicit indication sent by the UE.