1. The Chinese Univ. of Hong Kong Dept. of Computer Science & Engineering POWER-SPEED A Power-Controlled Real-Time Data Transport Protocol for Wireless Sensor-Actuator Networks (Based on the work submitted to WCNC 2007) Y. Zhou, E. Ngai, M. Lyu, and J. Liu Group Meeting 2006-11-21

2. 2 Outline Introduction Protocol Design Simulation Study Conclusions

3. 3 Introduction An example wireless sensor network

4. 4 Introduction An example wireless sensor-actuator network (WSAN) I, robot

5. 5 Introduction Features of WSANs Real-time data transport Mobile data sinks, i.e., the actuator nodes Stateless protocol is highly desired Battery-powered sensor nodes Energy-efficiency is still a critical issue

6. 6 Introduction Existing protocols for WSANs and WSNs Timeliness-domain QoS-guaranteed protocols SPEED, MMSPEED PREI (in MASS’06, by us) Feedback control packets are required To select fitful paths If feedback control packets can be avoided, … It would be This is the focus of this work

7. 7 Introduction Existing protocols for WSANs and WSNs GRP: Geographic Routing Protocol No feedback packets are required. No QoS guarantee

8. 8 Outline Introduction Protocol Design Simulation Study Conclusions

9. 9 Protocol Design Selecting next hop neighbor to which packets are forwarded Guarantee in-time delivery Achieve energy-efficiency Examples GRP Shortest-path based protocol

10. 10 Protocol Design Estimating QoS conditions of downstream links No feedback packets unaware of real QoS data Perform estimation Space domain: delay of upstream links Time domain: historical link delay

11. 11 Protocol Design Observation Encapsulate data in packet is more energy- efficient than send them individually Example Sending two 32-byte packets cost twice as much energy as sending one 64-byte packet Data on upstream-link conditions can be easily encapsulated in sensor reporting packets

12. 12 Protocol Design Part of POWER-SPEEDpacket header

13. 13 Protocol Design Link delay estimation Time domain Space domain SPEED Max hops

14. 14 Protocol Design Estimate the number of hops if delivering packet to a specific neighbor Candidate Those Required energy to send a packet to this neighbor Energy consumption estimation So, next-hop neighbor is the one that achieves minimum

15. 15 Protocol Design Summaries POWER-SPEED selects the next-hop neighbor based on the estimation of downstream path quality and the latency-bound requirement of packets. Adaptively it sends a packet that will expire in a longer period of time with lower transmitter power level to save energy that will expire sooner with higher transmitter power level, which results in fewer hop numbers between senders to destination actuators, and thus guarantees that the packet can reach its destination in a shorter period of time.

16. 16 Outline Introduction Protocol Design Simulation Study Conclusions

17. 17 Simulations

18. 18 Simulations Randomly place 100 nodes. Compare the performance of GRP and POWER-SPEED in terms of energy consumptions

19. 19 Simulations Randomly place 100-250 nodes. Compare the performance of GRP and POWER-SPEED in terms of energy consumptions

20. 20 Simulations Compare the performance of GRP and POWER-SPEED in terms of in-time packet delivery rate

21. 21 Outline Introduction Protocol Design Simulation Study Conclusions

22. 22 Conclusion We show a way to achieve real-time data transport without feed-back control packets We propose POWER-SPEED and show the effectiveness of the protocol

23. 23 Q & A