1. Energy-Efficient Protocol for Cooperative Networks IEEE/ACM Transactions on Networking, Apr. 2011 Mohamed Elhawary, Zygmunt J. Haas Yong Zhou 2012-07-19

2. 2/16 Outline  Introduction  Cooperative Protocol  Protocol Robustness and Energy Efficiency  Simulation Results  Conclusions

3. 2012-07-19 3/16 Introduction  Wireless sensor networks: limited energy resources  Cooperative transmission: Virtual antenna array Diversity gain Energy efficient

4. 2012-07-19 4/16 Cooperative Protocol - CwR  Cluster head, sending cluster, receiving cluster  Path width  Two phases: routing (AODV), recruiting-and- transmitting

5. 2012-07-19 5/16 Assumptions  Sending nodes are synchronized  Receiving power is the sum of all the signal powers coming from all the senders

6. 2012-07-19 6/16 CAN

7. 2012-07-19 7/16 Recruiting Phase

8. 2012-07-19 8/16 BER-MISO

9. 2012-07-19 9/16 Protocol Robustness (1)  Denote the transmission pattern of nodes in a sending cluster by a binary representation b m-1 … b 1 b 0 according to which node j transmits if b j = 1 and does not transmit if b j = 0.  Similarly, denote the reception status of nodes in a receiving cluster by a binary representation b m-1 … b 1 b 0 according to which node j correctly receives the packet if b j = 1 and receives the packet in error if b j = 0.

10. 2012-07-19 10/16 Protocol Robustness (2)

11. 2012-07-19 11/16 Protocol Robustness (3)

12. 2012-07-19 12/16 Other Protocols  Disjoint-paths:  One-Path

13. 2012-07-19 13/16 Failure Probability

14. 2012-07-19 14/16 Energy Consumption  To make the comparison of energy consumption of any two schemes meaningful, the failure probability needs to be kept equal for the compared schemes.  Thus, the needed transmission power for each case can be calculated according to the analysis of robustness.

15. 2012-07-19 15/16 Power Ratio

16. 2012-07-19 16/16 Conclusions  Propose an energy-efficient cooperative protocol  Analyze the robustness and energy consumption of the protocol