9.4 Optimized Idle-mode Mobility: E-UTRAN Access to cdma2000 HRPD Access

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

This procedure is used in the case the UE has a dormant HRPD session in the target HRPD network, either through the pre-registration procedure or previous HRPD attachment.

Figure 9.4-1: E-UTRAN to HRPD mobility in idle-mode

1. The UE is attached to E-UTRAN network and stay in ECM_IDLE state. The UE has a dormant HRPD session in the target HRPD network, either through the pre-registration procedure or previous HRPD attachment

2. The UE is in idle mode. Based on some trigger, the idle UE decides to perform cell re-selection to the HRPD system. Note, the cell re-selection decision can be made at any time when the UE is attached in the E-UTRAN network (including as soon as the UE has completed pre-registration).

3. The UE follows 3GPP2 procedures in [49] to inform the HRPD access network the UE has performed an inter-technology idle mode mobility event and is now tuned to HRPD.

4. The HRPD access indicates to the HSGW that the UE has moved to HRPD.

4a. The HS‑GW fetches the PDN GW identity for all the active PDN connections from the 3GPP AAA Server.

5~6. The HS‑GW exchanges a PMIP BU/BA with the PDN GW. The UE address information in PMIP BA returns the IP Address assigned to the UE. In this message, the Charging ID is also carried for charging correlation purposes. At this point the user plane is switched in the PDN GW towards the HRPD access network via the HS‑GW. Multiple PDN connections to the same APN can be supported using PDN connection identities in the same way as it is specified for S2a procedures.

6a. The PDN GW executes a PCEF-Initiated IP CAN Session Modification Procedure with the PCRF as specified in TS 23.203 [19] to obtain any new QoS policy and charging rules for all the active sessions as a result of the handover procedure. Since steps 6 and 6a are both triggered by the Proxy Binding Update in step 5, steps 6 and 6a may occur in parallel.

6b. The PDN GW informs the 3GPP AAA Server of its PDN GW identity and the APN corresponding to the UE’s PDN Connection and obtains authorization information from the 3GPP AAA Server. The message includes information that identifies the PLMN in which the PDN GW is located. The 3GPP AAA Server may update the information registered in the HSS as described in clause 12.

For multiple PDN connections, steps 5‑6 and 6a‑6b are performed for each PDN connection.

7. The HS‑GW acknowledges the HRPD access network.

8. At any time after step 6, the P‑GW shall initiate the PDN GW Initiated PDN Disconnection procedure as defined in clause 5.6.2.2, so that any resources are released in the EPS serving nodes that were serving the UE in E‑UTRAN access before the idle-mode mobility to HRPD took place.