Section: 4.5.1.3.4 Paging response for CS fallback
Content: The network may initiate the paging procedure for CS services when the MS is IMSI attached for CS services via EMM combined procedures, as described in 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [120]. At reception of an indication of paging for CS services from EMM, the MS shall stop timer T3246, if it is running. The MM sublayer in the MS requests EMM to perform the service request procedure for CS fallback. After the MS changes to a GERAN or UTRAN cell, the MS shall: - In A/Gb mode: ask for the establishment of an RR connection and proceed as if a paging has been received in the lower layers; - In Iu mode: ask for the establishment of an RRC connection and respond with the PAGING RESPONSE message defined in 3GPP TS 44.018[ None ]  [84], subclause 9.1.25. For reasons of backward compatibility the paging response shall use the RR protocol discriminator. If the MS determines, before sending the response to paging, that it is in a different location area than the stored location area, the MS shall initiate a normal location updating procedure first, regardless of Network Mode of Operation. Additionally the MS performs routing area updating as specified in subclause 4.7.5. If the location area of the current cell is not available, the MS may initiate a normal location updating procedure directly. When initiating the location updating procedure, the MS shall indicate "CS fallback mobile terminating call" in the Additional update parameters IE and the MS shall not include the MS network feature support IE. The MM connection establishment is delayed until successful completion of the normal location updating procedure. After the completion of the normal location updating procedure, the MS shall not send the PAGING RESPONSE message. NOTE: For the race condition when the mobile station has a CM application request pending, the mobile station also indicates that it has a follow-on request pending.