1. X50-20100125-xxx ZTE Discussion on cdma2000 Charging with PCC Title: Discussion on handover indicator transfer in S2a Sources: China Telecom, Huawei, Alcatel-Lucent Contact: CT: Peirong Xie (xiepr@gsta.com)xiepr@gsta.com Wenyi Li (liwenyi@gsta.com)liwenyi@gsta.com Huawei: Jixing Liu (liujixing@huawei.com)liujixing@huawei.com Alcatel-Lucent: Mike Dolan (Mike.Dolan@alcatel-lucent.com)Mike.Dolan@alcatel-lucent.com Recommendation: Review and concept approve the proposed method to determine the handover type The contributors 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 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 contributors. The contributors 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.

2. 2 Background  The Handover Indicator option is a mandatory mobility option in the PBU when handover occurs. It is described in 3GPP TS29.275.  Set to the value "2" (Handoff between two different interfaces) in case the handover is an inter access handover (i.e. from 3GPP to non-3GPP, from non-3GPP to 3GPP, or between two non-3GPP accesses) and IP address(es) preservation decision is taken; or  Set to the value "3" (Handoff between mobile access gateways for the same interface) in case the handover is an intra access (i.e. between two 3GPP accesses) handover; or  Set to the value "4" (Handoff state unknown) in case the handover is an inter access handover (i.e. from 3GPP to non-3GPP, from non-3GPP to 3GPP, or between two non-3GPP accesses) and IP address(es) preservation decision is negative or unknown.

3. 3 Problem Statement  Consider the case where A13/A16 and H1 are not deployed inter-vendor in an eHRPD network, and the UE moves from one vendor’s RAN to another vendor’s RAN, with the result that the UE is attached to a different HSGW by the second RAN.  The UE will discover its attachment to a new HSGW when it receives the LCP Configure-Request from the new HSGW.  In order to continue its current PDN connections, the UE must send a VSNCP Configure-Request message for each existing PDN connection, with Attach Type = “handoff attach”.  PROBLEM: The HSGW will not be able to determine whether the UE has come from LTE or from eHRPD, and so will not know whether to set the Handover Indicator option in the PBU to “2” or “3”.  Several solutions are reviewed in the following slides.

4. 4 Method 1—— Add a new value to Attach Type  There is “Attach Type” in the VSNCP configuration options defined in X.S0057. It is possible to indicate to the HSGW whether the UE has come from LTE or eHRPD using this parameter.  In current specifications, “Attach Type” has only two valid values:  1—“Initial Attach” to a PDN;  3—“Handover” attach to a PDN;  Solution: Add a new value “2” to Attach Type, and modify the meaning of value 3 as below.  1—“Initial Attach” to a PDN;  2—“Intra-RAT handover” to a PDN;  3—“Inter-RAT handover” to a PDN;  If the HSGW receives Attach Type “2”, it will set the Handover Indicator to “3”; If HSGW receives Attach Type “3”, it will set the Handover Indicator to “2”.

5. 5 Method 1 (Cont.)  Problem: For method 1, if the HSGW does not recognize the newly defined attach type value “2”, it may lead to the inability of the UE to receive service.  Possible alternative: Add a new option in VSNCP to deliver the type of the RAT that the UE is coming from, instead of using a new Attach Type value. See Method 2.  Problem: There may be roaming issues if an upgraded UE roams into an eHRPD network that has non-upgraded HSGWs. The UE may not be able to receive service.  Possible solution: Add a new capability indicator bit in X.S0057 section 10.1.11 to allow the UE to determine that the HSGW supports this new Attach Type value.

6. 6 Method 2 —— Add a new option for old RAT type  Add a new VSNCP configuration option to indicate to the HSGW the RAT type of the access network that the UE has just left.  Problem: If the UE includes this new option with the RAT type = “eHRPD”, an HSGW that is not upgraded will ignore the option, and will include a Handover Indicator option of “2” in the PBU. This may cause confusion at the P-GW and service impacts to the user.  The result of this is that the eHRPD operator should upgrade all HSGWs to support this new option, before introducing UEs that support and use the option.  There may be roaming problems, if upgraded UEs roam into a network with HSGWs that are not upgraded, they may have difficulty getting service.  Possible solution: Add a new capability indicator bit in X.S0057 section 10.1.11 to allow the UE to determine that the HSGW supports this new RAT Type option.

7. 7 Method 3 —— PGW judges HO type by RAT Type and Access Technology Type option information  “Access Technology Type option” is mandatory in PBU message;  “RAT Type” is also mandatory in Create Session Request message;  PGW compares the new access type with the old one. If they are same, handover type is set to “3”; otherwise set to “2”.  Drawback:  Need to modify 3GPP specification.  3GPP may not accept this solution because it does not utilize the Handover Indicator option which is existing in the current 3GPP specification. This option was created to help the P-GW know whether the handover was inter-RAT or not.

8. 8 Recommendations  Both Method 1 and Method 2 are possible, if the HSGW and UE support the new capability bit described for each Method.  We suggest to adopt Method 1 to determine the value that the HSGW should place in the Handover Indicator option on the PBU for intra-eHRPD handovers.

9. 9 Thanks