Non-optimized Handoff Enhancement 2017/4/24 Non-optimized Handoff Enhancement China Telecom Chengli Mei meichl@ctbri.com.cn Ericsson Ahmad Muhanna ahmad.muhanna@ericsson.com Ke-Chi Jang ke-chijang@ericsson.com HUAWEI Zhiming Li lizhiming@huawei.com Jie Zhao zhao.jie@huawei.com 13 September. 2010 Notice The contributors grants 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 contributors 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 contributors to assist 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 the contributors. The contributors specifically reserves the right to amend or modify the material contained herein and nothing herein shall be construed as conferring or offering licenses or rights with respect to any intellectual property of the contributors other than provided in the copyright statement above.

Motivation Enabling eHRPD-LTE dual mode UE to early-register on eHRPD directly over eHRPD access. slide 2

Working assumptions and Key Features Based on Single Transmitter / Dual Receiver (1T/2R) UE or Single Transmitter / Single Receiver (1T/1R) UE Minimizes changes to the current standards and network elements Key Features – (1T/1R) UE Step 1: UE selects and camps on LTE first without any interaction with eHRPD system Step 2: UE performs eHRPD early-registration directly over eHRPD access during LTE idle state. Step 3: UE could maintain eHRPD session during LTE idle state Step 4: Handover Phase – UE HO from LTE to eHRPD Key Features – (1T/2R) UE Step 1: UE can camp on either LTE or eHRPD first. Step 2: UE performs eHRPD early-registration directly over eHRPD access: During idle state if camped on LTE first. If UE camp on eHRPD first, UE may perform early-registration on eHRPD first and then move to LTE. Step 3: UE should be able to maintain eHRPD session during LTE idle state Step 4: Handover Phase – UE HO from LTE to eHRPD in case the UE camps on LTE first. slide 3

Early-Registration over eHRPD Access Call Flow (UE camps on LTE first) UE powers on UE finds a candidate cell of LTE UE camps on the LTE network If eNB broadcasts the eHRPD Neighbor cell list, the UE will tune to eHRPD mode to perform session establishment when the UE is in LTE idle state. UE stays in idle and finds a candidate eHRPD cell UE and HSGW can negotiate the capability of early-registration over eHRPD access during LCP UE switches to eHRPD network and performs early-registration over eHRPD access If Attach Type = “Registration”, HSGW does not setup bearer path with P-GW. Only default PDN connection must to be setup. The UE can optionally establish non-default PDN connection UE switches back to LTE 10. UE Switches back to LTE , slide 4

Details of early-Registration Upon receiving the eHRPD neighbor cell list broadcasted by eNB, UE initiates early-registration directly over eHRPD access. UE and HSGW negotiate the capability of early-registration over eHRPD access during LCP. If the HSGW doesn’t support it, UE may terminates the PPP session setup. UE establishes the default PDN connection with HSGW. The new attach type “Registration” indicates that no PMIP tunnel needs to be setup. UE can optionally establish the non-default PDN connections with HSGW. slide 5

Roaming Cases Analysis Network Capability UE Capability non-optimized handoff with early-registration. Normal non-optimized handoff Optimized handoff (S101) Optimized handoff (S101) and non-optimized handoff with early-registration non-optimized handoff with early-registration Non-optimized with early-registration early-registration attempt no PPP context Normal Non-optimized handoff Optimized handoff Support Registration over S101 Optimized Handoff using S101 Optimized handoff and non-optimized handoff with early-registration Optimized handoff using S101 slide 6

PPP Session Maintenance Full PPP context The UE and the HSGW have full PPP context after the early registration The HSGW supports PPP inactivity timer, and the UE knows the MAX PPP Inactivity Timer value For dual receiver case, UE may receive the LCP Echo-Request from HSGW, and sends Echo-Reply in idle state For single receiver case, if the UE fails to reply the Echo-Request, the HSGW and the UE enter to partial UE context Partial UE context The HSGW supports UE Context Maintenance timer If UE requests one or more PDN connections, HSGW stops the UE Context Maintenance timer, and re-start the PPP inactivity timer How the UE and the HSGW maintain the partial context, as currently documented in X.S0057 If PPP inactivity timer expires and the UE is NOT able to send any activity, the UE should assume that the context is gone. However, the UE always can check on the context when goes to eHRPD by sending echo-request with PDN-ID to check if the HSGW still maintains that context slide 7

Handover Call Flow slide 8 If Attach Type = “Handover”, HSGW initiates PMIP procedure based on all PDN context received during early registration slide 8

The details of Handover (1/2) Full PPP context If UE setups multiple PDN connections during early registration, UE will send one VSNCP message with “Handoff” attach type and PDN-ID(s) to trigger the HSGW perform PMIP procedure. UE initiates the TFT process Partial UE context UE establishes all PDN connections No PPP context UE establishes the PPP session slide 9

The details of Handover (2/2) PMIP trigger HSGW doesn’t trigger the PMIP Binding when the HSGW receives A11-Registration Request message with Active-Start Airlink Record. It is little different from current spec. Upon receiving the VSNCP with attach type = handover and one or more PDN-ID from UE, HSGW shall trigger the PMIP Binding PDN Synchronization The UE doesn’t need to keep the PDN connections information which is in eHRPD is synchronized with one’s in LTE all the time, UE only update the PDN connections information in eHRPD when it is in idle state in LTE UE shall perform the PDN connections information synchronization with HSGW via LCP echo during handover Accounting For the early-registration and session maintenance, the HSGW doesn’t start accounting process slide 10

Deployment Consideration & Standards Impacts Node Deployment impacts Standard impacts eNB eNB needs to broadcast SIB8, including eHRPD related cell parameters and subnet info None MME SGW eAN/ePCF Legacy AN needs to be software upgraded to evolved AN/ePCF HSGW Needs to support an additional attach type ” Registration” Add one new Attach type “Registration” in VSNCP Config-Req message. (X.S0057) HSS Should be deployed to support the SWx interface AAA . Need to support STa and SWx for authentication & authorization. . Need to support S6b. PDN GW Need to support S6b PCRF UE slide 11

Recommendation Adopt the early-registration over eHRPD access solution in X.P0057 -A slide 12

Backup Informative Only slide 13

eHRPD Session Maintenance – KeepAlive Procedures slide 14

The details of KeepAlive Process Concept: If UE is in Active state, it will set a flag and wait until getting to idle state, at which time UE will switch to eHRPD to maintain the session. Details: UE keeps a counter NKeepAliveReq. The counter increase by one when UE detects a period of eHRPD’s inactivity for TSMPClose/NSMPKeepAlive minutes. Case 1: If 0< NKeepAliveReq < NSMPKeepAlive, UE will set a flag. When UE enters LTE idle mode and the flag is set, UE will tune to eHRPD and send KeepAliveRequest message. Reset NKeepAliveReq to 0 and reset the flag. Case 2: If NKeepAliveReq = NSMPKeepAlive, UE has two options: 1) UE immediately tune to eHRPD and send KeepAliveRequest message. Reset NKeepAliveReq to 0 and reset the flag. In this scenario, the service in LTE is interrupted. 2) UE gives up the eHRPD session maintenance, just keep the service in LTE NSMPKeepAlive is set to max 3 per C.S0024. slide 15

eHRPD Session Maintenance – Subnet Change Note1: For the single receiver case, UE may receive the subnet info from the eNB Note2: For the dual receiver case, if QuickConfig or SectorParameters message received while UE in LTE active mode, the UE will defer UATI Assignment to when it goes into LTE idle state slide 16

LTE Paging and UL Data Process early-registration phase For the dual receiver case, UE may receive Paging message LTE Stop/abort HRPD registration procedures and tune to LTE Uplink Data ready for Transmission KeepAlive Continue HRPD KeepAlive procedure and tune to LTE Buffer data. Complete HRPD KeepAlive procedure and tune to LTE Subnet change Stop/abort HRPD UATI Assignment procedures and tune to LTE PPP context maintenance slide 17