1. Long Cheng †‡, Jiannong Cao ‡, Canfeng Chen §, Hongyang Chen ∥, Jian Ma §, Joanna Izabela Siebert ‡ † State Key Lab of Networking & Switching Tech., Beijing Univ. of Posts and Telecomm., China ‡ Department of Computing, Hong Kong Polytechnic University, Hong Kong § Nokia Research Center, Beijing, China ∥ Institute of Industrial Science, The University of Tokyo, Tokyo, Japan C OOPERATIVE C ONTENTION -B ASED F ORWARDING FOR W IRELESS S ENSOR N ETWORKS ACM IWCMC 2010

2. Outline Introduction Related Works Goals Assumption Cooperative Contention-Based Forwarding (CCBF) Simulation Conclusion 2

3. Introduction Geographic routing 3 Source Sink Poor link quality Unreliable link Interference Overhear transmissions

4. Introduction 4 Source How to choose the cooperative node? Sink B

5. Introduction Cooperative – PHY Layer SenderReceiver Cooperative node (CN) SenderReceiver Cooperative node (CN) 5

6. Introduction Cooperative – MAC Layer SenderReceiver Cooperative node (CN) 6

7. CBF (Cluster-based forwarding) Related Works Sender A D C Sink Distant helper B nexthop 7 Intermediate helper

8. CBF Sender A nexthop B C D Data Slot for distant helperSlot for intermediate helper Sender A D C Sink Distant helper Intermediate helper nexthop B New nexthop RTSCTS New nexthop Data 8

9. CBF (Cluster-based forwarding) Related Works Sender A D C Sink Intermediate helper B nexthop 9

10. CBF Sender A nexthop B C D Data Slot for distant helperSlot for intermediate helper Sender A D C Sink Distant helper Intermediate helper nexthop B New nexthop RTSCTS New nexthop Data 10

11. CRL (Cooperative Relaying and Leapfrogging) Related Works Sender A D C Sink LPF B 1)Didn’t receive RTS from A. 2)Overhear a data packet from C. Lea PF rog Node nexthop 11 Relay

12. CRL Sender A nexthop B C LPF D Data Sender A D C Sink LPF nexthop B LOSS Data Timer ACK D terminates the forwarding process of B. D becomes a new sender. RTSCTSACK 12 Relay

13. Related Works – Disadvantage D Destination C B nexthop Sender A helper t0：A→Bt0：A→Bt0：A→Bt0：A→B t1：C→Bt1：C→Bt1：C→Bt1：C→B t2：D→Bt2：D→Bt2：D→Bt2：D→B Sender A nexthop B C Data LOSS Data D duplications Hidden helper problem Packet duplications Hidden helper problem Packet duplications 13

14. Goals Select better next-hop. – increasing the average advance per hop (AAPH) Avoid packet duplications. 14 DS C A B

15. Assumption Every node knows – Its location. – Neighbor locations. – Destination and its location. 15

16. Cooperative Contention-Based Forwarding (CCBF) Sender A E D Destination C B nexthop Overview 16

17. CCBF Phase I – Nexthop Selection Phase II – Cooperative Forwarding 17

18. CCBF Next-Hop Selection Sender A B C E RTSCTS Backoff C = t(sender, C, dest.) Backoff E = t(sender, E, dest.) Backoff B = t(sender, B, dest.) Sender A E C B 18 Destination

19. d Next-Hop Selection CCBF 19 Sender A 19 NODE B B Dist 141-116 = 25 PRR 0.91 C C 141-133 = 8 0.79 E E 141-104 = 37 0.41 EADV 22.75 6.32 15.17 NODE B B C C E E Dist(B,d) = 116 PRR B = 0.91 Dist(B,d) = 116 PRR B = 0.91 Dist(E,d) = 104 PRR E = 0.41 Dist(E,d) = 104 PRR E = 0.41 Dist(C,d) = 133 PRR C = 0.79 Dist(C,d) = 133 PRR C = 0.79 Dist(A,d) = 141 T max t(s,n,d) (backoff) t(s,n,d) (backoff) B E Packet reception ratio C

20. CCBF Next-Hop Selection Sender A B C E RTSCTS Backoff C = t(sender, C, dest.) Backoff E = t(sender, E, dest.) Backoff B = t(sender, B, dest.) Sender A E C B nexthop Data CTS Cancels backoff. 20 Destination

21. CCBF Phase I – Nexthop Selection Phase II – Cooperative Forwarding 21

22. CCBF Cooperative Forwarding – Cooperative Area 1)received the data packet 2)received the CTS 3)positive advances toward the destination 22

23. CCBF Cooperative Area Sender A E D Destination C B nexthop Cooperative Area 1) Received the data packet 2) Received the CTS 3) Positive advances toward the destination 23

24. CCBF Cooperative Forwarding Sender A E C B nexthop Sender A B C E RTSCTS Backoff C Backoff E Backoff B Data ACK Cancels backoff. Data Phase IPhase II ACK ACK Cancels backoff. … 24

25. CCBF Next-hop receiver B and it serves as the actual forwarder. Sender A B RTSCTS Phase IPhase II ACK Data … Sender A E Other node B Nexthop & forwarder 25

26. CCBF The helper E serves as the actual forwarder. Sender A B RTSCTS Phase IPhase II ACK Data … E CONF (confirmation) Data Sender A E Other node B Nexthop Forwarder 26 Other node (A’s neighbors)

27. Simulation ParameterValue SimulatorNS-2 Sensing range40m Map size200m*200m T max 0.01s T SIFS 10  s T DIFS 50  s 27

28. Simulation (0,0) (200,200) Source Sink 200m 28

29. Simulation 29

30. Simulation 30

31. Simulation 31

32. Simulation 32

33. Conclusion CCBF avoids packet duplications. In simulations, – Increasing the average advance per hop – Improving the end-to-end energy e ffi ciency and latency – Improving the packet loss ratio 33

34. T hanks f or y our a ttention