1. Link-Utility-Based Cooperative MAC Protocol for Wireless Multi-Hop Networks Yong Zhou, Ju Liu, Lina Zheng, Chao Zhai, He Chen National Mobile Communications Research Laboratory School of Information Science and Engineering, Shandong University, Jinan, China IEEE Transactions on Wireless Communications, vol. 10, no. 3, March 2011, pp. 995–1005

2. Outline Introduction Related Word Goals System Model Link-utility-based cooperative MAC (LC-MAC) Simulation Conclusion

3. Introduction Obstacles of realizing the full potential of delivering packets –Channel fading –Signal interference

4. Introduction Multiple-input multiple-output (MIMO) systems on a single node can improve signal quality –Limited physical size –Cost constraints

5. Introduction Cooperative Transmissions –Virtual antenna array Improve signal quality Enhance the performance of both throughput and energy-efficiency

6. Introduction Cooperative Coding: Alamouti code (2  1) –Two-node cooperation: 2 transmit antennas, 1 receive antenna Two-node cooperation is better than multi-node cooperation Orthogonal code design is not available for more than two cooperation nodes without decreasing data rate [23] [23] Y. Fan and J. Thompson, “MIMO configurations for relay channels: theory and practice,” IEEE Trans. Wireless Commun., vol. 6, pp. 1774-1786, May 2007.

7. Introduction Compared to the single-input single-output (SISO) link –Virtual MISO link can achieve diversity gain –Reflect into a decrease in the reception threshold at the receiver [19] S. M. Alamouti, “A simple transmit diversity technique for wireless communications,” IEEE JSAC, vol. 16, pp. 1451-1458, Oct. 1998. [20] Y. Zhou, J. Liu, C. Zhai, and L. Zheng, “Two-transmitter two-receiver cooperative MAC protocol: cross-layer design and performance analysis,” IEEE TVT, vol. 59, no. 8, pp. 4116-4127, Oct. 2010.

8. Related Work All existing cooperative MAC protocols are mostly –designed for wireless single-hop networks –two-phase cooperative transmission N AB  1. Direct Transmission [12] T. Guo and R. Carrasco, “CRBAR: Cooperative relay-based auto rate MAC for multirate wireless networks,” IEEE Transactions on Wireless Communications, vol. 8, no. 12, pp. 5938–5947, Dec. 2009. O 2. Relay-based transmission

9. Related Work CRBAR [12] does not fully exploit –the broadcast nature of wireless multi-hop networks [12] T. Guo and R. Carrasco, “CRBAR: Cooperative relay-based auto rate MAC for multirate wireless networks,” IEEE Transactions on Wireless Communications, vol. 8, no. 12, pp. 5938–5947, Dec. 2009. FNL SABD FNL SABD S → A → N → B → L → D S → {A, F} → B → L → D CRBAR [12] This paper partner relay

10. Goal Design a novel link-utility-based cooperative MAC protocol (LC-MAC) with distributed helper selection in wireless multi-hop networks –link throughput –energy consumption P O N C M RQT KI GFH E NJL SABD

11. System model Channel state information (CSI) can be estimated by receivers Each node –is equipped with one Omni-directional antenna –has a maximum transmission power (P X ) constraint

12. System model maximum transmission power (P X ) constraint –P t : Transmission Power –H: channel gain between the transmitter and receiver –N 0 : noise variance –P I : total interference power at receiver –: reception threshold   ≥ 10  /10 (  0 +   ) / |  | 2

13. System model Channel state information (CSI) can be estimated by receivers Each node –is equipped with one Omni-directional antenna –has a maximum transmission power (P X ) constraint

14. LC-MAC: transmission types Transmission Type, which is determined by the best helper –CT 1 : one-phase cooperative transmission (partner) –CT 2 : two-phase cooperative transmission (relay) –DT: direct transmission (transmitter) P O N C M RQT KI GFH E NJL SABD

15. LC-MAC: transmission types Partners of A: E, F –Partners have currently received data packets from S –CT 1 : one-phase cooperative transmission P O N RQT KI GFH E NJL SABD C M

16. LC-MAC: transmission types Relays of A: G, H, I, N –Relays have not currently received data packets from S –CT 2 : two-phase cooperative transmission P O N C M RQT KI GFH E NJL SABD

17. LC-MAC: transmission types A: no suitable helper –DT: direct transmission P O N C M RQT KI GFH E NJL SABD

18. LC-MAC: CT 1 LC-MAC: distributed three-stage backoff scheme –One-phase cooperative transmission

19. LC-MAC: CT 1 LC-MAC: distributed three-stage backoff scheme –One-phase cooperative transmission P O N RQT KI GFH E NJL SABDAB FC M

20. LC-MAC: CT 1 RTS: Extension of the 802.11 RTS frame –Carry the length of data packets (L) in bits –A waits for CTS frame: T RTS + T SIFS + T CTS P O N RQT KI GFH E NJL SABDAB F RTS SNR(A→F) C M

21. LC-MAC: CT 1 CTS: Extension of the 802.11 CTS frame –Carry the instantaneous SNR of direct link –B sets data packets timeout: T CTS + T inter + T intra + T re + T RTH + 3T SIFS P O N RQT KI GFH E NJL SABDAB F CTS SNR(B→F), SNR(B→A) C M

22. LC-MAC: CT 1 Power and rate of A and F should be set the same –F: P O N RQT KI GFH E NJL SABD CTS RTS C M SNR1(B→A) SNR2(B→F)

23. LC-MAC: CT 1 Link utility (LU) = U – cE –U: link throughput –E: energy consumption AB F

24. LC-MAC: CT 2 LC-MAC: distributed three-stage backoff scheme –Two-phase cooperative transmission AB N

25. LC-MAC: CT 2 LC-MAC: distributed three-stage backoff scheme –Two-phase cooperative transmission P O N RQT K JL SABD CTS RTS C M I GHNF E AB N SNR1(A→N) SNR2(N→B)

26. LC-MAC: CT 2 The appropriate power of N –N: P O N RQT K JL SABD CTS RTS C M I GHNF E SNR1(A→N) SNR2(N→B)

27. LC-MAC: CT 2 Link utility (LU) = U – cE –U: link throughput –E: energy consumption AB N

28. LC-MAC: helper selection LC-MAC: distributed three-stage backoff scheme –Inter-group contention (G) –Intra-group contention (M) –Re-contention (K)

29. LC-MAC: helper selection P O N RQT K JL SABD C M I GHNF E GNF I H E GFN –Re-contention (K) –Inter-group contention (G) –Intra-group contention (M) F

30. LC-MAC: DT LC-MAC: distributed three-stage backoff scheme –Direct transmission

31. Simulation Setup Four-hop chain topology network Nodes are uniformly distributed in 400x200 m 2 area

32. Simulation Results

36. Conclusion A link-utility-based cooperative MAC (LC-MAC) protocol with distributed helper selection for wireless multi-hop networks is proposed. –Jointly adjust Transmission type Power Rate TheEND