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
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).
The UE follows 3GPP2 procedures in 3GPP2 C.S0087-0 
to inform the HRPD access network the UE has performed an inter-technology idle mode mobility event and is now tuned to HRPD.
The HRPD access indicates to the HSGW that the UE has moved to HRPD.
The HS GW fetches the PDN-GW identity for all the active PDN connections from the 3GPP AAA Server.
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.
The PDN-GW executes a PCEF-Initiated IP CAN Session Modification Procedure with the PCRF as specified in TS 23.203
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.
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.
The HS GW acknowledges the HRPD access network.
At any time after step 6, the P-GW shall initiate the PDN-GW Initiated PDN Disconnection procedure as defined in clause 22.214.171.124
, 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.