Section: 4.7.1.7 Intersystem change between A/Gb mode and Iu mode
Content: For the Iu mode to A/Gb mode and A/Gb mode to Iu mode intersystem change the following cases can be distinguished: a) Intersystem change between cells belonging to different RA's: The procedures executed by the MS depends on the network mode of operation in the old and new RA. If a change of the network operation mode has occurred in the new RA, then the MS shall behave as specified in subclause 4.7.1.6. If no change of the network operation mode has occurred in the new RA, then the MS shall initiate the normal or combined routing area updating procedure depending on the network operation mode in the current RA. b) Intersystem change between cells belonging to the same RA: 1) If the READY timer is running in the MS in A/Gb mode before or after the inter-system change occurs,or the MS is in PMM-CONNECTED mode in Iu mode, before the inter-system change occurs then the MS shall perform a normal or combined routing area updating procedure depending on the network mode of operation in the current RA. 2) If the READY timer is not running in the MS in A/Gb mode before the inter-system change occurs, or the MS is in PMM-IDLE mode in Iu mode before the inter-system change and the READY timer is not running in the MS in A/Gb mode after the intersystem change, then, unless a routing area updating procedure is required according to case c) or case b) 3) below or according to subclause 4.7.5.1 and 4.7.5.2.1, the MS shall not perform a routing area updating procedure until uplink user data or signalling information needs to be sent from the MS to the network. - If the MS is in the same access network(i.e. A/Gb mode or Iu mode), as when it last sent user data or signalling messages, the procedures defined for that access system shall be followed. This shall be sending of an LLC PDU in an A/Gb mode cell or initiating the service request procedure in an Iu mode cell. - If the MS is in a different access network (i.e. A/Gb mode or Iu mode), as when it last sent user data or signalling messages, the normal or combined routing area updating procedure shall be performed depending on the network operation mode in the current RA, before the sending of user data or signalling messages. If the signalling message is a DETACH REQUEST indicating "power off", the routing area updating procedure need not to be performed. - If the periodic routing area update timer expires the MS shall initiate the periodic routing area updating procedure. 3) If the READY timer is not running in the MS in A/Gb mode or the MS is in PMM-IDLE mode in Iu mode, then the MS shall perform a normal or combined routing area updating procedure depending on the network mode of operation in the current RA if the MS is required to perform routing area updating for IMS voice termination as specified in annex P.3. 4) If the READY timer is not running in the network in A/Gb mode or the network is in PMM-IDLE mode in Iu mode, then the network shall page the MS if downlink user data or signalling information needs to be sent from the network to the MS. This shall include both A/Gb mode and Iu mode cells. - If the MS receives the paging indication in the same access network (i.e. A/Gb mode or Iu mode), as when it last sent user data or signalling information, the MS shall send any LLC PDU in a A/Gb mode cell or shall initiate the service request procedure indicating service type "paging response" in an Iu mode cell. - If the MS receives the paging indication in a different access network (i.e. A/Gb mode or Iu mode), as when it last sent user data or signalling information, the MS shall perform a normal or combined routing area updating procedure depending on the network operation mode in the current RA. c) Intersystem handover from A/Gb mode to Iu mode during a CS connection: After the successful completion of the handover from an A/Gb mode cell to an Iu mode cell, an MS which has performed the GPRS suspension procedure in Gb mode (see 3GPP TS 44.018[ None ]  [84]) (i.e. an MS in MS operation mode B or an DTM MS in a A/Gb mode cell that does not support DTM) shall perform a normal routing area updating procedure in the Iu mode cell in order to resume the GPRS services in the network, before sending any other signalling messages or user data.