X xxx Pre-Registration Context in eHRPD 1 Pre-Registration Context Removal in eHRPD System Sources: China Telecom, ZTE Contact: Li Bi YiFeng Rajesh Bhalla ABSTRACT: As a UE pre-registered on the eHRPD system detaches from E-UTRAN access, the pre-registration information on eHRPD system is useless and must be removed ASAP. Recommendation: Review and concept approve The contributing companies grant a free, irrevocable license to 3GPP2 and its Organizational Partners to incorporate text or other copyrightable material contained in the contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner's name any Organizational Partner's standards publication even though it may include all or portions of this contribution; and at the Organizational Partner's sole discretion to permit others to reproduce in whole or in part such contribution or the resulting Organizational Partner's standards publication. The contributing companies are also willing to grant licenses under such contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for purpose of practicing an Organizational Partner’s standard which incorporates this contribution. This document has been prepared by the contributing companies to assist in the development of specifications by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to be construed as a binding proposal on contributors. The contributing companies specifically reserve the right to amend or modify the material contained herein and to any intellectual property of contributors other than provided in the copyright statement above.

X xxx Pre-Registration Context in eHRPD 2 Pre-Registration Scenario For optimized handover from the E-UTRAN access to the eHRPD access, the UE first performs ‘pre-registration’ with the eHRPD system via E-UTRAN radio and the S101 interface –Pre-registration on the eHRPD system includes setup of the A10/A11 connection(s), establishment of the PPP session, Authentication and Authorization on the eHRPD access network, and establishment of PDN connection(s) and the TFT(s) After the UE has pre-registered on the eHRPD system, it may not handover to the eHRPD for quite some time –As long as the E-UTRAN radio can support the services, the UE stays in the coverage of E-UTRAN and maintains the eHRPD pre-registration as well –Only if the E-UTRAN radio cannot support the services, would the UE perform HO procedures to switch the UE from the E-UTRAN access to the eHRPD access

X xxx Pre-Registration Context in eHRPD 3 Problem Description While pre-registered on eHRPD system, the UE may Detach from E-UTRAN: –UE sends Detach Request message to the E-UTRAN to release the resources and context information in the EPS –Resources associated with eHRPD pre-registration are useless UE releases such resources on E-UTRAN Detach But no procedures have been specified to gracefully release eHRPD resources associated with the pre-registration context for such a scenario UE S-GW MME HSGW P-GW LTE eHRPD Pre-registration context on eHRPD system and the UE UE S-GW MME HSGW P-GW LTE eHRPD Detach What happens to the pre-registration context on eHRPD system ? ? ?

X xxx Pre-Registration Context in eHRPD 4 Possible Solutions Solution # 1 ： –As the UE detaches from the E-UTRAN access, MME informs the eHRPD system of the ‘detach’ event via the S101 interface –On receipt of ‘detach’ notification over S101 interface, the eAN/ePCF forwards ‘detach’event notification to the HSGW via an A11-RRQ message –The HSGW then performs ‘HSGW Initiated UE Detach’ procedures as specified in section of X.S v2.0 Solution # 2 ： –As the UE detaches from the E-UTRAN access, MME informs the eHRPD system of the ‘detach’ event via the S101 interface –On receipt of ‘detach’ notification over S101 interface, the eAN/ePCF sends an A11-RRQ with ‘detach’notification to the HSGW. The eAN/ePCF removes all UE associated resources and context as well –On receipt of ‘detach’ notification, the HSGW also releases all resources and context associated with the UE Solution # 3 ： –Use the PPP Inactivity Timer and PPP Link Status Determination procedures as specified in section of X.S v2. Solution # 4 ： –Use “HSS/AAA initiated UE detach procedure” to delete the Pre-registration information in eHRPD system.

X xxx Pre-Registration Context in eHRPD 5 Call Flow for Solution # 1

X xxx Pre-Registration Context in eHRPD 6 Call Flow for Solution # 2

X xxx Pre-Registration Context in eHRPD 7 Analysis of Solution # 3 Solution # 3: Timer Based approach Timer based approach is usually used for handling abnormal cases, and not for (normal) event processing scenarios. For example: –As the UE detaches from E-UTRAN system, it sends a ‘detach request’ message to notify the EPS to delete UE context, and does not rely on a Timer. As long as the UE can use message based procedures to inform the EPS of an event, timer based approach is not used. –If the UE gets out of the coverage of E-UTRAN and the MME cannot find the UE for a long time, then the timer based approach will be used. If the associated Timer expires, the context related to the UE will be deleted. This is an abnormal case because the UE can not inform the EPS of an event using a message based procedures. Asynchronous States at the UE and on the eHRPD: –UE also has state information related to the pre-registration. The UE removes such pre- registration information as it detaches from E-UTRAN. Therefore any pre-registration state/context maintained on the eHRPD system will be useless even if the UE re-attaches to the eHRPD/E-UTRAN soon thereafter. –As per the currently specified procedures in X.S0057, PPP Link Status Determination procedures will result in the pre-registration state/context to be maintained on the eHRPD for sufficiently long period of time (PPP Inactivity Timer default value: 86,4000 seconds ) –Asynchronous Pre-Registration States at the UE and the eHRPD: pre-registration state/context information stays on eHRPD for sufficiently long time whereas such state/context information removed from the UE

X xxx Pre-Registration Context in eHRPD 8 Analysis of Solution # 4 Although the HSS/AAA can initiate detach procedure, it can not initiate “pre-registration information deletion”. –Pre-registration does not have PMIP tunnel, radio bearer, and UE’s storage of pre-registration information. And if it is used, there may be some errors.

X xxx Pre-Registration Context in eHRPD 9 P-GW Analysis of Solution # 4 UE S-GW/MME Non-3GPP AGW 3GPP access PDN connection 1 PDN connection 2 PDN connection 3 HSS/AAAP-GW Non-3GPP access Figure: MAPCON When UE detaches from 3GPP access, in which case the UE just wants to tear down the 3GPP access but keep the non-3GPP access, if the HSS/AAA initiates the “non-3GPP detach procedure”, that would lead to error because the UE does not want to tear down the non-3GPP access. So HSS/AAA initiated detach procedure can not be used to delete pre- registration information.

X xxx Pre-Registration Context in eHRPD 10 Proposal Adopt Solution # 1

X xxx Pre-Registration Context in eHRPD 11 Thanks!