3GPP2 Femto Cell Workshop:System Selection, Interference

Management, Handoffs and Mobility

Ed Tiedemann

15 October 2007

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Presentations

• John Burgess, Alcatel-Lucent– Femtocell System Selection

• Minsh Den, Airvana– Femto Access Control Provisioning and Enhanced System Selection

• Manoj Deshpande, Qualcomm– Femto Cells –Search and System Selection

• Balaji Raghothaman, Airvana– Femto Air Interface Enhancements for Future Mobile Devices

• Balaji Raghothaman, Airvana– Femto Air Interface Deployment Modeling, Simulation, and Performance

• Mingxi Fan, Qualcomm– Interference Management in Femto-Cell Deployment

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Femto Cell Association

• Open access– All MS can use femto cell

• Restricted access– Only specific MS can use femto cell– Family, friends, visitors

• Signaling access– MS can receive signaling (may be limited) from femto

• 911 issues– Restricted assocation– Position– Backhaul failures

• Emergency broadcast issues

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Some Basics

• Femto Cell Identity– Use NID– Use BASE_ID– Use (SID, NID, REG_ZONE)

• Same or Separate Carriers– Same carrier as macro cell– Separate carrier– Femto cells can be on a set of carriers

• 1x and DO typically take two carriers

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Femto Cell Selection for Legacy Mobiles

• Two classes– Those that can update PRL– Those that cannot make PRL changes

• Use PRL– Include femto cell in PRL– May cause MS to search frequently for femto cell– Mechanisms to construct PRLs need to be developed

• Use GNLM– As long as neighbor is 3 dB stronger, the MS will choose– May limit the range of femto-cells– May require additional use of restricted assocation mechanisms

• Use Beacon– May impact other mobiles; additional network interference– May needs to be on multiple frequencies– Adds complexity to femto cell– May require additional use of restricted assocation mechanisms

• Registration, filter, redirect (SRDM)– Mobile will periodically check for femto; battery life issues

• Global Service Redirection Message (GSRM)

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Possible Modifications to Enhance System Selection

• Two basic extreme approaches– Select first, reject– Select right

• Use position location to indicate to MS when to search

• Use user zones on Forward Link– Already in standards– User Zone Identification Message (UZIM)– Private Neighbor List Message (PNLM)– Limited number of user zones

• Use PRL enhancements, such as PUZL in IS-683/C.S0016)– Allows PRL (PUZL) for femto cells to be separated from existing lists– Black lists– Add range/masks for NIDs and BASE_IDs– Would need to be done for DO– May want to reexamine whether another mechanism is preferable

• Mechanisms to update lists

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Interference Issues

• Co-channel Macro-Femto deployment– MS using femto cell on same frequency as macro cell

• Femtocell deployment on a carrier adjacent to a macro-cell carrier– Adjacent channel rejection

• In dense femto cell deployments inter-femto outage scenarios

must be addressed– More than just dense; any close coupling between femto cells

• Modeling of interference between femto cells

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RF Issues

• Frequency interference and planning– Is a frequency reuse used over a set of frequencies

• PN offset allocation– Is a small number used? Otherwise need to expand GNLM size significatly (there is a

size limit)– Reuse pattern– Ambiguity at the macro cell level

• Femto cell transmit power– Power classes

• Femto cell emissions and other RF specifications

• MS using femto cell can cause interference to macro cells or other femto cells

• How to limit MS output power– Limit data rate when possible– Introduce limit for MS output power– Possibly have MS report output power to femto cell

• Reduce minimum size of PN search window

• Reverse Link silence periods– Synchronized or unsynchronized

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Other

• Smart femto cells– Learn environment

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Handoff

• For handoff into femto, ambiguity of PILOT_PN– Does MS need to report other information