1. Delay-aware Routing in Low Duty-Cycle Wireless Sensor Networks Guodong Sun and Bin Xu Computer Science and Technology Department Tsinghua University, Beijing, China IEEE Wicom 2011

2. Outline Introduction Network model Algorithm design Simulation evaluation Conclusion

3. Introduction Advances in microelectronics, wireless networking make wireless sensor networks applicable – Civilian – Military

4. Introduction Sensor nodes work relying on – Capacity-small – Unrechargeable batteries

5. Introduction Energy consumption of Sensor nodes – Idle listening – Packet overhearing

6. Introduction To save sensors’ energy and then prolong the system lifetime – Low duty-cycle active sleep Sensor sleep

7. Introduction Problem experienced by low duty-cycle sensor networks – Long delivery delay caused by the sleep latency of sensors The delay is critical to the performance of systems – Military surveillance – Target tracking – Monitoring

8. Goal Designing a delay-aware routing algorithm for low duty-cycle sensor networks – Reduce the network delay – Data packet drop rate

9. Network model N sensor nodes L*L square Communication range = r Multi-hop

10. Network model Duty cycle of sensor – Active – Sleep active sleep Sensor A sleep EX: duty cycle = 40% (5|1,5)

11. Network model Channel access – CSMA/CA like method REQ/CLR – Successful transmission Locations of node A,B and other node K

12. Network model Delay model – Queuing delay – Transmission delay – Propagation delay Node A’s queue packet1 packet2 packet3 active ….……… Sensor B active Queuing delay:

13. Algorithm design Two phases – Network initializing – Dynamic forwarding

14. Network initializing ID Working schedule Layer number A S C D B Broadcast message

15. Network initializing Layered topology A S C D B 0 1 11 2

16. Dynamic forwarding Forwarding set – F A ={S} – F B ={S} – F C ={S} – F D ={B,C} A S C D B 0 1 11 2 B : (100|5,30,62) C : (100|3,24,30)

17. Dynamic forwarding Forwarding sequence – S D ={C,B,C,C,B,B} Node D’s queue packet1 packet2 packet3 CBCCBBCBCCBB A S C D B 0 1 11 2 B : (100|5,30,62) C : (100|3,24,30) 3 5 24 30 62

18. Performance analysis Simulation setup Comparison – Static shortest-path routing(SSPR) parametervalue Square area of side150 Work schedule length150τ / 1τ=20ms Packet generate rate3 packets / 5minutes

19. Simulation result 150 sensors

20. Simulation result 150 sensors

21. Simulation result 150 sensors

22. Simulation result Duty cycle = 5%

23. Simulation result Duty cycle = 5%

24. Simulation result Duty cycle = 5%

25. Simulation result Sensor density = 8, duty cycle = 5%

26. Simulation result Sensor density = 8, duty cycle = 5%

27. Simulation result Sensor density = 8, duty cycle = 5%

28. Conclusions The authors proposed a delay-aware routing algorithm for low duty-cycle sensor networks – Achieves shorter delay by dynamically selecting forwarders Simulation results demonstrate that our algorithm improves – delivery delay – Reduces the network drop rate – Saving the energy of sensors

29. 29 Thanks for your a ttention