1. A Wakeup Scheme for Sensor Networks: Achieving Balance between Energy Saving and End-to-end Delay Xue Yang, Nitin H.Vaidya Department of Electrical and Computer Engineering, and Coordinated Science Laboratory University of Illinois at Urbana-Champaign IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS 2004) Speaker: Hao-Chun Sun

2. Outline Introduction Introduction Related Work Related Work Pipelined Tone Wakeup Scheme (PTW) Pipelined Tone Wakeup Scheme (PTW) Analysis for Energy Consumption Analysis for Energy Consumption Performance Evaluation Performance Evaluation Conclusion Conclusion

3. Introduction Wireless Sensor Network Wireless Sensor Network Application scenarios — Application scenarios — Intrusion detection Intrusion detection Disaster alarming Disaster alarming The communication is typically driven by events and events occur rather infrequently. The communication is typically driven by events and events occur rather infrequently. Sensors spend a considerable fraction of lifetime to monitor the environment, said to be in the monitoring state. Sensors spend a considerable fraction of lifetime to monitor the environment, said to be in the monitoring state. Once events are detected, sensors may need to leave the monitoring state and actively communicate with each other. Once events are detected, sensors may need to leave the monitoring state and actively communicate with each other.

4. Introduction WSNs are characterized by the limited energy supply. WSNs are characterized by the limited energy supply. It is generally desired to turn off a sensor ’ s radio when there is no need for communication. It is generally desired to turn off a sensor ’ s radio when there is no need for communication.

5. Introduction Allowing radio to be turned off research directions have been taken to preserve the communication capability of WSNs — Allowing radio to be turned off research directions have been taken to preserve the communication capability of WSNs — Spatial redundancy Spatial redundancy Topology management schemes maintain network connectivity. Topology management schemes maintain network connectivity. Temporal potential in energy saving Temporal potential in energy saving Wake up mechanism wake the radio up when communication is necessary. Wake up mechanism wake the radio up when communication is necessary.

6. Introduction Motivation of this paper — Motivation of this paper — Wakeup schemes have great potential in energy saving for sensor networks where events occur infrequently. Wakeup schemes have great potential in energy saving for sensor networks where events occur infrequently. Existing wakeup schemes encounter critical tradeoffs between energy saving and wakeup delay. Existing wakeup schemes encounter critical tradeoffs between energy saving and wakeup delay. Ex: a message forward 10 hops on average. Ex: a message forward 10 hops on average. Wakeup delay: 1.3 s  end-to-end delay: 13 s Wakeup delay: 1.3 s  end-to-end delay: 13 s Object Tracking: object speed — 120km/h Object Tracking: object speed — 120km/h 13s  433 m 13s  433 m

7. Introduction Motivation of this paper — Motivation of this paper — Propose a wakeup scheme Propose a wakeup scheme Helps to achieve the balance between energy saving and end-to-end packet delay. Helps to achieve the balance between energy saving and end-to-end packet delay.

8. Related Work Wake schemes Wake schemes Synchronous schemes Synchronous schemes Ex: IEEE 802.11 power saving mechanism Ex: IEEE 802.11 power saving mechanism It is hard to be implemented in large WSNs. It is hard to be implemented in large WSNs. Asynchronous schemes Asynchronous schemes “ Power-saving protocols for IEEE 802.11-based Multi-hop Ad Hoc Networks. ” IEEE Computer and Communication Societies, 2002. “ Power-saving protocols for IEEE 802.11-based Multi-hop Ad Hoc Networks. ” IEEE Computer and Communication Societies, 2002. The objective is to arrange the wakeup schedule so that any two neighboring nodes are guaranteed to detect each other in finite time. The objective is to arrange the wakeup schedule so that any two neighboring nodes are guaranteed to detect each other in finite time.

9. Related Work The power saving capability and wakeup delay can be improved by using an additional wakeup channel. The power saving capability and wakeup delay can be improved by using an additional wakeup channel. There is a low power wakeup radio — There is a low power wakeup radio — The wakeup radio can stay awake for the entire time. The wakeup radio can stay awake for the entire time. Drawback: Drawback: The low power wakeup radio usually has a smaller transmission range than the high power data radio. The low power wakeup radio usually has a smaller transmission range than the high power data radio. Two same capability radio — Two same capability radio — STEM (Sparse Topology and Energy Management) STEM (Sparse Topology and Energy Management) MobiHoc 2002 MobiHoc 2002

10. Related Work STEM (Sparse Topology and Energy Management) — STEM (Sparse Topology and Energy Management) — Two radio Two radio Wakeup radio Wakeup radio Periodically turns on for T dstem every T duration Periodically turns on for T dstem every T duration is defined as the duty cycle ratio. is defined as the duty cycle ratio. Data radio Data radio Sleep until wakeup mechanism alerting. Sleep until wakeup mechanism alerting. Wakeup radio Sleep Duty Time T dstem Sleep T

11. Related Work STEM (Sparse Topology and Energy Management) — STEM (Sparse Topology and Energy Management) — Wake Operation Wake Operation Sender Receiver Others TwTw T wack Duty Time Sleep TwTw Turn on Data radio Duty Time Turn on Data radio

12. Related Work STEM (Sparse Topology and Energy Management) — STEM (Sparse Topology and Energy Management) — Minimum duty time Minimum duty time Not synchronized Not synchronized When bit rate is low, T dstm could be large. When bit rate is low, T dstm could be large. T has to be large enough to achieve the desired energy saving, resulting in a large wakeup delay. T has to be large enough to achieve the desired energy saving, resulting in a large wakeup delay. Sender Receiver Sleep TwTw T wack TwTw Duty Time T dstem

13. Pipelined Tone Wakeup Scheme PTW — PTW — Two radio Two radio Wakeup radio Wakeup radio Periodically turns on for T dtone every T duration Periodically turns on for T dtone every T duration is defined as the duty cycle radio. is defined as the duty cycle radio. Data radio Data radio Sleep until wakeup mechanism alerting. Sleep until wakeup mechanism alerting. Wakeup radio Sleep Duty Time T dtone Sleep T

14. Pipelined Tone Wakeup Scheme Using the Wakeup Tone Using the Wakeup Tone Wake Operation — Wakeup Channel Wake Operation — Wakeup Channel Sender Receiver Others Duty Time Sleep TpTp Turn on Data radio Duty Time Turn on Data radio Tone

15. Pipelined Tone Wakeup Scheme Using the Wakeup Tone Using the Wakeup Tone Wake Operation — Data Channel Wake Operation — Data Channel Sender Receiver Others Data Transmission Turn off Data radio Data Notification ACK

16. Pipelined Tone Wakeup Scheme Using the Wakeup Tone Using the Wakeup Tone T dtone ≧ t d + T transit T dtone ≧ t d + T transit t d : tone detection time (200μs) t d : tone detection time (200μs) T transit : sleep  receive duration (518μs) T transit : sleep  receive duration (518μs) T p = 2 × T dtone + T sleep = T + T dtone T p = 2 × T dtone + T sleep = T + T dtone Sender Receiver Sleep TpTp T dtone T sleep False probability: 10 -3 Detection probability:99.1% TR1000 RF Module using ASK

17. Pipelined Tone Wakeup Scheme PTW — PTW — A wakes up all its neighbors Wakeup Channel Data Channel A notify B t0 t1t2 B wakes up all its neighbors A sends a data packet to B B notify C C wakes up all its neighbors t3t4 A sends a data packet to B t5 … … ABCDEF TpTp T data T data = Queuing delay + Channel access delay + transmission delay + Propagation delay T p ≦ T data 10ms~hundreds of ms Satisfy!!

18. Analysis for Energy Consumption Analysis Model — Analysis Model — Total node: N Total node: N Number of neighbors of S: N s Number of neighbors of S: N s Monitoring state: T event Monitoring state: T event Assume: T w = T wack Assume: T w = T wack T dstem = 2T w +T wack = 3T w = 3T wack T dstem = 2T w +T wack = 3T w = 3T wack Power of Transmisson, Receive, Idle: P Power of Transmisson, Receive, Idle: P S D A4 A3 A2 A1 TTT … t Wakeup radio t Data radio Sleep Data Wakeup procedure T event

19. Analysis for Energy Consumption One Wakeup Procedure — One Wakeup Procedure — The sender S The sender S STEM — STEM — PTW — PTW — Compare — Compare — Ex: Duty stem =10, Duty tone =100 Need T event > 6.03T

20. Analysis for Energy Consumption One Wakeup Procedure — One Wakeup Procedure — The receiver D The receiver D STEM — STEM — PTW — PTW — Compare — Compare — Ex: Duty stem =10, Duty tone =100 Need T event > 5.56T

21. Analysis for Energy Consumption One Wakeup Procedure — One Wakeup Procedure — The other neighboring nodes A The other neighboring nodes A STEM — STEM — PTW — PTW — Compare — Compare — Ex: Duty stem =10, Duty tone =100 Need T event > 5.93T

22. Analysis for Energy Consumption One Wakeup Procedure — One Wakeup Procedure — The Loose Bound for T event The Loose Bound for T event Taking into account that Duty stem and Duty tone ≧ 1 Taking into account that Duty stem and Duty tone ≧ 1 Ex: wakeup and Ack packet size: 144 bits tone detection time: 100μs Bit Rate=3x144/100=4.3Mbps In most application, It is not likely a low cost sensor will be equipped.

23. Analysis for Energy Consumption Multiple Wakeup Procedures — Multiple Wakeup Procedures — The Loose Bound for T event The Loose Bound for T event H: The max number of wakeup procedures a node is involved upon an event. H: The max number of wakeup procedures a node is involved upon an event. Ex: Duty stem =10, Duty tone =100, H=5 Need T event > 102T

24. Performance Evaluation Simulator: The modified version of ns-2 Simulator: The modified version of ns-2 Radio power: TR1000 (20m) Radio power: TR1000 (20m) Wakeup packet size: 144 bits Wakeup packet size: 144 bits Data packet size: 1040 bits Data packet size: 1040 bits Data Ack size: 128 bits Data Ack size: 128 bits Bits Rate: 2.4Kbps Bits Rate: 2.4Kbps T dstem =225ms, Duty stem =13.33 T dstem =225ms, Duty stem =13.33 T dtone =1ms, Duty tone =229 T dtone =1ms, Duty tone =229

25. Performance Evaluation Cluster Scenario — 55 nodes  11 clusters Cluster Scenario — 55 nodes  11 clusters Source: Node 0, Destination: Node 50 Source: Node 0, Destination: Node 50 Path:0  5  10  15  20  25  30  35  40  4 5  50 (Ten events with 100s period) Path:0  5  10  15  20  25  30  35  40  4 5  50 (Ten events with 100s period) Extreme case: All node will be awakened. Many nodes will be awakened multiple times. Extreme case: All node will be awakened. Many nodes will be awakened multiple times. 55

26. Performance Evaluation Cluster Scenario — Cluster Scenario — Individual Energy Consumption (Joule) Individual Energy Consumption (Joule) Source Forward nodeNF-NeighborSink

27. Performance Evaluation Cluster Scenario — Cluster Scenario — Total energy consumption & end-to-end delay Total energy consumption & end-to-end delay 10 hops 10 hops

28. Performance Evaluation Random Generated Networks — Random Generated Networks — 10 random topologies are generated. 10 random topologies are generated. 100 nodes 100 nodes Square area: 79.25m x 79.25m Square area: 79.25m x 79.25m Average number of neighbor each node: 20 Average number of neighbor each node: 20 As different values of Duty stem in STEM trade off energy with delay. As different values of Duty stem in STEM trade off energy with delay. STEM1 — Duty stem =5.33 STEM1 — Duty stem =5.33 STEM2 — Duty stem =13.33 STEM2 — Duty stem =13.33 10 events 10 events

29. Performance Evaluation Random Generated Networks — Random Generated Networks —

30. Conclusion It has presented a Pipelined Tone Wakeup (PTW) scheme for sensor network, which helps to achieve the balance between energy saving and end-to-end delay. It has presented a Pipelined Tone Wakeup (PTW) scheme for sensor network, which helps to achieve the balance between energy saving and end-to-end delay. The use of wakeup tone enables a large duty cycle ratio without causing a large wakeup delay at each hop. The use of wakeup tone enables a large duty cycle ratio without causing a large wakeup delay at each hop. It helps the pipeline to hide most of the wakeup delay while achieving a major energy saving. It helps the pipeline to hide most of the wakeup delay while achieving a major energy saving.