Inter-cell Mitigation for 802.16m
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE S802.16m-08/583
Date Submitted:
2008-07-14
Source:
Chang-Lan Tsai, Ren-Jr Chen, Chung-Lien Ho
Yan-Xiu Zheng, Richard Li
ITRI
Wern-Ho Sheen
NCTU/ITRU
E-mail: {tsaichangl, richard929}@itri.org.tw
Venue:
Call for Contributions of IEEE 802.16m_08/024 on the topic of “Interference Mitigation”
Base Contribution:
IEEE C802.16m-08/583r1
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.
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Frequency Reuse Factor
• Frequency reuse 1
– Same frequency is reused by each sector
– High spectral efficiency
– Large inter-cell interference
• Cell edge users can rarely retain connection
Bandwidth
power
P
Cell
frequency
Sector 2
BS with
directional
antenna
Sector 1
Sector 3
Frequency Reuse Factor
• Frequency reuse 3
– Same frequency is reuse every 3 sectors
– Low spectral efficiency
– Low inter-cell interference
• Cell edge users have fairly good connection quality
power
P
 1
Bandwidth
Cell
Sector 2
BS with
directional
antenna
Sector 1
Sector 3
power
power
frequency
P
P
frequency
frequency
Fractional Frequency Reuse
• Different frequency reuse factor in one sector
– Sector edge band using frequency reuse 3
• Allocated to the cell edge users
– Sector center band using frequency reuse 1
• Allocated to the users in the center of the sector
Sector center
band
power
Cell
P
1  1
Sector edge
band
1 P
frequency
Sector 2
BS
Sector 1
power
P
1 P
frequency
Sector 3
power
P
1 P
frequency
Soft Fractional Frequency Reuse
• To compensate the spectral efficiency loss due to
fractional frequency reuse
– The reserved band at each sector is allocated for center users
with restricted power
 2  1, 2  1
Sector center
band
power
Cell
P
Sector edge
band
2P
2 P
frequency
Sector 2
BS
Sector 1
power
P
2P
2 P
2 P
frequency
Sector 3
power
P
2P
2 P
frequency
Flexible Fractional Frequency Reuse
• Semi-static fractional frequency reuse
– The ratio of sector center and sector edge bands is adaptive to
traffic load, user distribution, etc.
Sector center
band
power
P
Sector edge
band
3 P
 4  1, 4  1
3  1, 3  1
Soft frequency reuse 3
power
3 P
4P
4 P
frequency
power
P
3 P
3 P
frequency
power
3 P
4P
4 P
4 P
frequency
power
P
3 P
frequency
power
3 P
frequency
4P
4 P
frequency
Proposed Text
11.x Interference Mitigation
11.x.y Interference suppression by fractional frequency
reuse
Fractional frequency reuse (FFR) scheme should be supported to
improve average and cell-edge user throughput. The ratio of
different frequency reuse factor and the corresponding power level
are optimized or adjusted adaptively according to the traffic load
and user distribution, etc., to trade of between spectral efficiency
and average/cell-edge user throughput enhancement. Coordination
between BSs for frequency partition is needed to avoid/suppress
inter-cell/sector interference.