1 Title:Using group of artificial pilots to identify target femtocell during active hand-in Source:Peerapol Tinnakornsrisuphap, Ravindra Patwardhan QUALCOMM Incorporated {peerapol, Date:August 13 th, 2009 Recommendation:Review and Adopt Notice ©2009. All rights reserved. QUALCOMM Incorporated 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. QUALCOMM Incorporated is 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 QUALCOMM Incorporated 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 QUALCOMM Incorporated. QUALCOMM Incorporated 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 QUALCOMM Incorporated other than provided in the copyright statement above.

Outline  Problem Overview  Proposed Solution  Architecture  Recommendations 2

Problem Overview  For active (i.e., connected) handoff of a MS/AT from macro base stations or access networks to femtocell, the macro system needs to be able to uniquely identify the target femto access point  PN offset, which is used for macro-macro handoff, is no longer sufficient due to many factors  More femtocells than available PN offsets  Limited room for listing neighbor PNs in Neighborlist message in macro base stations 3

Current solutions and drawbacks (1) 4  Solution 1: Mobile sensing  For supporting legacy 1x MS, TSG-A defined “Measurement Request/Response” messages for requesting multiple candidate target femtocells to detect the presence of the MS on the RL  Subsequently, the Femto Convergence Server (MSC-equivalence) decides which femtocell that the MS has the best FL to based on comparing the reports from femtocells  Reference : A r0  Drawbacks  Scalability concern with a large number of femtocells  Cannot have 100% accuracy due to FL/RL imbalances

Current solutions and drawbacks (2) 5  Solution 2 : 1x Rev E – HSIN message  In 1x Rev E, a femtocell can advertise “Access Point Identification” message which contains the IOS_MSC_ID and IOS_CELL_ID that the MS can report in “Handoff Supplementary Information Notification” message during active handoff  This allows the macro BS to uniquely determine the target femtocell  Reference: C  Drawbacks  The macro BS needs to be upgraded to support Handoff Supplementary Information Notification message  Does not support legacy MS

Observations (1) 6  In solution 2, the macro BS needs to be upgraded to receive unique femtocell identification for the target femtocell in the form of IOS_MSC_ID and IOS_CELL_ID  In hard handoff for legacy MS (and also in HRPD), only pilot measurements (e.g., PN Phases and Strengths) are reported  If unique femtocell identity can be created using information in PSMM (for 1x) or RouteUpdate (for HRPD), then macro base stations do not need to be upgraded to support active hand-in to femtocells

Observations (2) 7  In a given geographical region (e.g., under a macrocell), it is feasible to find several unused PN offsets  This in itself is not going to be enough for uniquely identifying all femtocells under a macrocell  Most likely, neighbor list message of the macrocell cannot support adding these many more PN offsets

Proposed Solution 8  Create unique signature for femtocell by advertising a group of PN Phases and Strength in APIDM  MS obtains the group of PN Phases from APIDM and then add theses group of PN Phases in PSMM (in 1x) or RouteUpdate (in HRPD) when handoff is triggered  PN offsets are chosen among a pool of unused PNs in area Assuming each femtocell is assigned 3 PNs out of pool of 15, then at least 455 unique identifiers can be generated. More if phase information is used.  PNs do not need to be advertised in macro neighbor list and are not transmitted in physical pilot  Pilot report is used in target MSC (for 1x) or target Femto Gateway (for HRPD) to determine target femtocell

Proposed fields in APIDM (both 1x and HRPD) 9 FieldLength (bits) HO_PNPhase_GROUP_INCL1 HO_PNPhase_GROUP_COUNT0 or 4 PN_Phase 0 or (15 x LOC_REC_LEN) Report_Strength0 or 6 where 1.HO_PNPhase_GROUP_INCL is set to 1 when the PN Phase group is advertised in APIDM 2.HO_PNPhase_GROUP_COUNT contains the number of PN Phases following this field 3.PN_Phase_GROUP contains an array of 9-bit fields, each listing PN Phase to be reported in PSMM/RouteUpdate 4.Report_Strength should be set to at least T_ADD

Example (1x) 10 Refer to 1x Femto Architecture in the appendix for reference

Example (HRPD) 11 Refer to HRPD Femto Architecture in the appendix for reference

How to populate PSMM? 12  For each PN phase listed in the “Handoff PN Phase Group”, the MS adds each PN phase in the PILOT_PN_PHASE field in PSMM in the order that is shown in APIDM  The MS populates the corresponding PILOT_STRENGTH field for each PN phase in PSMM with the corresponding pilot strength field in APIDM

Summary of Benefits 13  Only requires configuration on macro infrastructure  No upgrade needed on macro infrastructure to perform active handoff to femtocells  Handoff is always accurate  Scalable solution  Group of PN Phases can be expanded later as needed with no impact to deployed femtocells  Simple algorithm in FCS and FGW

Recommendations 14  Add Group of Pilot PN Phases to APIDM for both 1x and HRPD  Targeted specifications  1x Rev E addendum  HRPD Revision C

1x and HRPD femto network architecture Appendix 15

1x Femto System Architecture 16 FCS appears as target MSC to macro 1x infrastructure system and it can determine the target 1x FAP based on information in IS-41 FACDIR2 message

HRPD Femto System Architecture 17 FGW performs A16 proxy function to allow macro AN to handoff to femto system without changes to macro AN. FGW determines target FAP based on information in embedded RouteUpdate message in A16 interface