1. International Technology Alliance In Network & Information Sciences International Technology Alliance In Network & Information Sciences 1 Interference Subtraction with Supplementary Cooperation in Wireless Cooperative Networks TA1, Project 1 Zhengguo Sheng, Zhiguo Ding and Kin K. Leung Imperial College September 23, 2009

2. 2 Outline Introduction Introduction Supplementary cooperation (SC) Interference subtraction Conclusion

3. 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. 3

4. motivation for cooperative diversity 4 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

5. 5 Outline Introduction Supplementary cooperation (SC) Supplementary cooperation (SC) Interference subtraction Conclusion

6. Motivation for Supplementary Cooperation Observations –Broadcast nature of wireless transmission can be further explored –Cooperation can be extended across the CLs 6 S1 S2 S3 S4 R1 R2 R3 Cooperation? Yes T2 T1T3T4 T5 T6

7. Outage Probability of Supplementary Cooperation Propagation model: path loss and slow fading Channel Capacity: Outage Probability: By computing the limit, we have 7

8. BER Improvement with Supplementary Cooperation SC generates routes with a smaller number of hops and satisfactory BER when compared with CC 8 [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.

9. 9 Outline Introduction Supplementary cooperation (SC) Interference subtraction Interference subtraction Conclusion

10. Motivation for Interference Subtraction Observations –No interference is considered so far –Concurrent transmissions harm BER performance –One can further reduce interference from prior information 10 S1 S2 S3 R1 R2 R3 T1T2T3T4T5T6 S1(1) R1(1) S2(1) R2(1)S3(1)R3(1) S1(2) S4 T1T2T3T4T5T6T7 S1(1) R1(1) S2(1) R2(1)S3(1)R3(1) S1(2) R1(2) S2(2) S4(1) R2(2) S1(3)

11. Linear Network Analysis 11 A five-node linear network Assumption: Transmission range=1; Interference range=2; Interference free, d>2 Each node successfully receives a message on an average in every two time slots, the average throughput for direct transmission with interference subtraction is

12. 12 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%

13. 13 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

14. Conclusion 14 What we have done 1)Optimal solution: QoS routing algorithm for cooperative networks 2)Interference effects on BER performance 3)Throughput analysis Future works 1)Delay analysis 2)Multi-QoS solution; more insights on BER, delay and throughput 3)System performance for a general network scenario

15. Thank you 15