Section: P.3 Inter-system change between A/Gb mode and Iu mode
Content: An MS is required to perform routing area updating for IMS voice termination if: 1) the upper layers have indicated that the MS is available for voice calls in the IMS (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [120], subclause 3.1); 2) the MS is enabled for mobility management for IMS voice termination; 3) the "IMS voice over PS session indicator" received for Iu mode has the value "IMS voice over PS session supported in Iu mode, but not supported in A/Gb mode"; and 4) the voice domain preference for UTRAN as defined in 3GPP TS 24.167[ 3GPP IMS Management Object (MO); Stage 3 ]  [134] is not "CS voice only".