1. Flexible Frequency Reuse for 16m IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE C802.16m-08/588 Date Submitted: 2008-07-xx Source: Kwanhee Roh, Jeongho Park, Jaehee ChoVoice:+82-31-279-4863 Samsung ElectronicsE-mail:kwanhee.roh@samsung.comkwanhee.roh@samsung.com 416 Maetan-dong, Yeongtong-gu Suwon-si, Gyeonggi-do, Korea * http://standards.ieee.org/faqs/affiliationFAQ.html Venue: IEEE 802.16m-08/024 “Call for Comments and Contributions on Project 802.16m System Description Document (SDD)” in response to the following topic: “Interference Mitigation” Base Contribution: None Purpose: To be discussed and adopted by TGm for use in 802.16m SDD Notice: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. Introduction Flexible Frequency Reuse –Each reuse set(F1, F2, F3 and F4) experiences different interferences Higher interference in FRF=1 region Lower interference in FRF=3 region –Trade-off between throughput and cell edge performance can be controlled by adjusting the amount of reserved resources (un-used resource in FRF 3 region) High inter-cell interference Low inter-cell interference

3. Issues of FFR Reduced BW efficiency –Available subchannels are decreased when FFR is employed –SNR gain with FFR is not enough to compensate the loss caused by bandwidth reduction –Spectral efficiency in cell boundary can be increased but overall throughput may decrease!  Need to enhance/optimize FFR

4. Enhanced FFR Compensate BW reduction by re-using reserved resource allocating to those MSs with good channel condition –MSs located close to BS can be serviced with low transmit power Low transmit power can prohibit severe interference to edge MSs in neighbor cells Transmit power in reserved resource region should be carefully controlled –Upper limit of transmit power can be controlled by coordination between adjacent cells

5. Simulation Result Enhanced FFR –Use subchannels in reserved region with low TX power (mostly allocated to MSs located within cell center area) FFR evaluation result –Enhanced FFR outperforms static FFR in avg throughput but slight degradation of edge spectral efficiency FFR (Partial Loading = 26.7%) N/AStaticAggressive Avg throughput (kbps)480444494675 Ratio (%)100%92.6%97.3% Lower 5% SE (bps/Hz)0.3440.4830.473 Ratio (%)100.00%140.48%137.56%

6. Conclusion FFR can enhance spectral efficiency in the cell edge area But total average throughput may be degraded due to the reduction of usable subcarriers in each cell If subcarriers in reserved zone can be re-used for MSs located in cell center area with only small TX power, the degradation due to FFR can be compensated

7. Proposed Text x.x.x Inter-cell interference mitigation - Flexible Frequency Reuse Flexible Frequency Reuse may be used to help users suffering from severe inter-cell interference. FFR can limit the usage of frequency resources in each cell such that part of frequency resources can be restricted to use according to the coordination between cells. Restriction can be achieved by leaving the resources unused or by lowering down the transmission power in those resources. - Control signals for inter-cell interference mitigation MSs measure RSSI from neighbor BSs and report to serving BS. Coordination between BSs are performed by means of backbone network.