ronald y. chang†, zhifeng tao ◊, jinyun zhang ◊ and c.-c. jay kuo† †ming hsieh department...
DESCRIPTION
Introduction Inter-cell interference(ICI) MS frequencyTRANSCRIPT
A Graph Approach to Dynamic Fractional Frequency Reuse (FFR) in Multi-Cell OFDMA Networks
Ronald Y. Chang†, Zhifeng Tao◊, Jinyun Zhang ◊ and C.-C. Jay Kuo††Ming Hsieh Department of Electrical Engineering and Signal and Image Processing Institute University of Southern California◊ Mitsubishi Electric Research Labs (MERL)
ICC 2009
Outline
Introduction System description Previous interference management schemes Proposed dynamic FFR scheme using the
graph approach Simulation results Conclusion
Introduction
Inter-cell interference(ICI)
MS
MS
MS
MS MS
MS
MS
MS
frequency
Introduction
Inter-cell interference
MS
MS
MS
MS MS
MS
MS
MS
frequency
Introduction
Inter-cell interference
MS
MS
MS
MS MS
MS
MS
MS
frequency
Introduction
Modification all these schemes are of fixed configuration
Goal Enhance overall cell throughput and service rate
System description
downlink cellular system with L BSs, each serving M(l) MSs, l = 1, 2, ... ,L
The downlink signal for MS m is sent with power Pm
System description
A set of N subchannels is available for resource allocation
slow fading (i.e., path loss)fast fading(i.e., Rayleigh fading)
anchor (or serving) BS for MS m
set of interfering MSs thermal noise density subchannel bandwidth
System description
The theoretical cell throughput(bits/sec) for cell l
set of MSs that are being served in cell l
System description
The service rate in cell l
cardinality of the set S(l)
Previous interference management schemes
Reuse-3
1
2
3Cell 1
Cell 2
Cell 3,44
Previous interference management schemes
Reuse-3
1
2
3
Cell 1 Cell 2 Cell 3,4
4
Previous interference management schemes
FFR-A
1
2
3
Cell 1 Cell 2 Cell 3
Previous interference management schemes
FFR-B
1
2
3
Cell 1 Cell 2 Cell 3
Proposed dynamic FFR scheme using the graph approach
Example scenario
BS1
BS2
BS3
MS2MS4
MS3MS5
MS1
Proposed dynamic FFR scheme using the graph approach
The graph construction rule for FFR-A MS a and MS b are users of the same cell MS a is a cell-edge user of cell i and MS b is a cell-
edge user of cell j, where cell i and cell j are neighbors
MS a is a cell-center user of cell i and MS b is a cell-edge user of cell j, where cell i and cell j are neighbors
BS1
BS2
BS3MS2MS4
MS5MS3
MS1
Proposed dynamic FFR scheme using the graph approach
The graph construction rule for FFR-A Interference graph
BS1
BS2
BS3MS2MS4
MS5MS3
MS1
MS1
MS2MS3
MS4
MS5
Cell 1 Cell 2 Cell 3
Proposed dynamic FFR scheme using the graph approach
The graph construction rule for FFR-B MS a and MS b are users of the same cell MS a is a cell-edge user of cell i and MS b is a cell-
edge user of cell j, where cell i and cell j are neighbors
BS1
BS2
BS3MS2MS4
MS5MS3
MS1
Proposed dynamic FFR scheme using the graph approach
The graph construction rule for FFR-B Interference graph
BS1
BS2
BS3MS2MS4
MS5MS3
MS1
MS1
MS2MS3
MS4
MS5
Cell 1 Cell 2 Cell 3
Proposed dynamic FFR scheme using the graph approach
a(x) is defined as the set of colors that may be used to color node x
MS1
MS2MS3
MS4
MS5
MS1
MS2MS3
MS4
MS5FFR-A FFR-B
Proposed dynamic FFR scheme using the graph approach
a(x) is defined as the set of colors that may be used to color node x
MS1
MS2MS3
MS4
MS5FFR-B
BS1
BS2
BS3MS2MS4
MS5MS3
MS1
Cell 1 Cell 2 Cell 3MS1
MS1={1,2,3}MS2={1,2,3}MS3={1,2,3}
MS4={1,2,3}MS5={1,2,3}
123
MS4={1,2}MS5={1,2}
Proposed dynamic FFR scheme using the graph approach
a(x) is defined as the set of colors that may be used to color node x
MS2MS3
MS4
MS5FFR-B
BS1
BS2
BS3MS2MS4
MS5MS3
MS1
Cell 1 Cell 2 Cell 3
MS5
123MS2={1,2,3}
MS3={1,2,3}
MS4={1,2}MS5={1,2}
MS3={1,3}MS4={1}
Proposed dynamic FFR scheme using the graph approach
a(x) is defined as the set of colors that may be used to color node x
MS2MS3
MS4
FFR-BBS1
BS2
BS3MS2MS4
MS5MS3
MS1
Cell 1 Cell 2 Cell 3MS4 1
23MS2={1,2,3}
MS3={1,3}
MS4={1}
MS2={2,3}
Proposed dynamic FFR scheme using the graph approach
a(x) is defined as the set of colors that may be used to color node x
MS2MS3
FFR-BBS1
BS2
BS3MS2MS4
MS5MS3
MS1
Cell 1 Cell 2 Cell 3
MS2
123MS2={2,3}
MS3={1,3}
Proposed dynamic FFR scheme using the graph approach
a(x) is defined as the set of colors that may be used to color node x
MS3
FFR-BBS1
BS2
BS3MS2MS4
MS5MS3
MS1
Cell 1 Cell 2 Cell 3
MS3
123
MS3={1,3}
Simulation results
Simulation results
The cell throughput in symmetric cell load scenarios
Simulation results
The service rate in symmetric cell load scenarios
Simulation results
The cell throughput in asymmetric cell load scenarios
Simulation results
The service rate in asymmetric cell load scenarios
Conclusion
A dynamic fractional frequency reuse (FFR) framework for multi-cell OFDMA networks was proposed in this work.
The dynamic feature is characterized by the capability of adjusting the spectral resource to varying cell load conditions.
The proposed dynamic scheme is shown to deliver higher cell throughput and service rate, especially in asymmetric cell load scenarios.