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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1000 1

2

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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

100

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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