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International Technology AllianceIn Network & Information Sciences
International Technology AllianceIn Network & Information Sciences
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Interference Subtraction with Supplementary Cooperation in Wireless Cooperative Networks
TA1, Project 1
Zhengguo Sheng, Zhiguo Ding and Kin K. Leung Imperial College
Interference Subtraction with Supplementary Cooperation in Wireless Cooperative Networks
TA1, Project 1
Zhengguo Sheng, Zhiguo Ding and Kin K. Leung Imperial College
September 23, 2009September 23, 2009
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Outline
IntroductionIntroduction
Supplementary cooperation (SC)
Interference subtraction
Conclusion
Introduction
• Cooperative diversity is a cooperative multiple antenna techniques which exploits user diversity by decoding the combined signal of the relayed signal and the direct signal in wireless multi-hop networks.
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motivation for cooperative diversity
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• Motivation for ad-hoc networks with cooperative transmission– Wireless links are unreliable due to multi-path propagation– Spatial diversity is bandwidth efficient to combat fading– Spatial diversity is difficult to achieve due to processing
complexity, power consumption, ...• Solution: Cooperative Transmission
– Allow users to share their antennas cooperatively to assist each other for successful reception
• Advantages of cooperative transmission: Virtual antenna array– Boosted reception reliability– Achieved higher data rates– Bandwidth efficient and increased coverage
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Outline
Introduction
Supplementary cooperation (SC)Supplementary cooperation (SC)
Interference subtraction
Conclusion
Motivation for Supplementary Cooperation
• Observations– Broadcast nature of wireless transmission can be
further explored – Cooperation can be extended across the CLs
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S1
S2 S3 S4
R1 R2R3
Cooperation? Yes
T2T1 T3 T4 T5 T6
Outage Probability of Supplementary Cooperation
• Propagation model: path loss and slow fading
• Channel Capacity:
• Outage Probability:
• By computing the limit, we have
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i,ji,j k/2
i,j
ad
h
BER Improvement with Supplementary Cooperation
• SC generates routes with a smaller number of hops and satisfactory BER when compared with CC
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3 4 5 6 710
-4
10-3
10-2
10-1
Total number of hops
End
-to-
end
BE
R
Conventional cooperationDirect transmissionSupplementary cooperation
34.87%
100 200 300 400 500 600 700 800 900 10000
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X (meters)
Y (
met
ers)
DV route Direct tranmissionRelay transmission
[1] Z. Sheng, Z. Ding and K. K. Leung, "On the Design of a Quality-of-Service Driven Routing Protocol for Wireless Cooperative Networks", proc. of IEEE Vehicular Technology Conference (VTC), Singapore, MAY 2008.
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Outline
Introduction
Supplementary cooperation (SC)
Interference subtractionInterference subtraction
Conclusion
Motivation for Interference Subtraction
• Observations– No interference is considered so far
– Concurrent transmissions harm BER performance
– One can further reduce interference from prior information
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S1 S2 S3
R1 R2 R3
T1 T2 T3 T4 T5 T6
S1(1) R1(1) S2(1) R2(1) S3(1) R3(1)
S1(2)
S4
T1 T2 T3 T4 T5 T6 T7
S1(1) R1(1) S2(1) R2(1) S3(1) R3(1)
S1(2) R1(2) S2(2)
S4(1)
R2(2)
S1(3)
Linear Network Analysis
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A five-node linear network
Assumption:Transmission range=1; Interference range=2; Interference free, d>2
Each node successfully receives a messageon an average in every two time slots, the average throughput for direct transmission with interference subtraction is
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Linear Network Analysis
A five-node linear network
For conventional cooperative transmission:a message on an average requires three time slots to be received, the average throughput is
For supplementary cooperative transmission:The average throughput is
24%
42%
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Interference Effects on BER Performance
• Channel resource reuse factor: spatial frequency reuse for scheduling • Link throughput can be increased without bring in significant BER• Trade-off between throughput, reuse factor and end-to-end BER
• Link throughput
is the desired transmission rate
is the reuse factor
1 2 3 4 5 6 7 8 910
-4
10-3
10-2
10-1
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Channel resource reuse factors
End
-to-
end
BE
R
3-hop CC without IS6-hop CC without IS9-hop CC without IS3-hop SC with IS6-hop SC with IS9-hop SC with IS
Conclusion
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What we have done1) Optimal solution: QoS routing algorithm for cooperative
networks
2) Interference effects on BER performance
3) Throughput analysis
• Future works1) Delay analysis
2) Multi-QoS solution; more insights on BER, delay and throughput
3) System performance for a general network scenario
Thank you
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