3GPP2 Femto Cell Workshop: System Selection, Interference Management, Handoffs and Mobility Ed Tiedemann 15 October 2007

2 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

3 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

4 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

5 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)

6 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

7 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

8 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

9 Other Smart femto cells –Learn environment

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