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 Cho Voice: +82-31-279-4863Samsung Electronics E-mail: kwanhee.roh@samsung.com416 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

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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

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

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

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/A Static Aggressive

Avg throughput (kbps) 4804 4449 4675

Ratio (%) 100% 92.6% 97.3%

Lower 5% SE (bps/Hz) 0.344 0.483 0.473

Ratio (%) 100.00% 140.48% 137.56%

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

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.