1. Efficient Energy Management Protocol for Target Tracking Sensor Networks X. Du, F. Lin Department of Computer Science North Dakota State University Fargo, ND 58105 USA 9th IFIP/IEEE International Symposium on Integrated Network Management (IM), 2005 (IM), 2005 Chien-Ku Lai

2. Outline Introduction Network Model The Sensor Network Energy Management Protocol The Routing Protocol Performance Evaluation Conclusions

3. Introduction - Wireless Sensor Networks Many low-power, low-cost small sensors distributed over a vast field to obtain fine-grained, high-precision sensing data typically powered by batteries usually scattered densely and statically

4. Introduction - Wireless Sensor Networks (cont.) A source A sensor node detecting a target and generating data to report the conditions of the target A sink An end user or a base station that collects data from the sources

5. Introduction (cont.) Most existing researches focus on issues in Network layer Media access control layer Physical layer  Application layer protocols for sensor networks remain a largely unexplored region

6. Network Model

7. Cell a: side length a = r r = sensing range R: transmission range R/r ≧ 2

8. Network Model - Assumptions 1. Sensor nodes are static, and each sensor node is aware of its own location SNEM protocol does not require very accurate node locations 2. For most cells, there is at least one sensor node in each cell

9. The Sensor Network Energy Management Protocol (SNEM) 1. About target tracking 2. Concepts 3. Details 4. Power balance

10. The Sensor Network Energy Management Protocol (SNEM) Where is the energy spent The main task of a sensor node is to detect events perform quick local data processing transmit the data Power consumption domains Sensing Communication Data processing  SNEM mainly considers how to save energy in communication domain

11. The Sensor Network Energy Management Protocol (cont.) Node idle listening consumes 50–100% of the energy required for receiving Stemm and Katz idle:receive:send ratios are 1:1.05:1.4 The Digitan 2 Mbps Wireless LAN module idle:receive:send ratios is 1:2:2.5 The idea of SNEM let nodes that do not perform sensing task go to sleep

12. SNEM - About target tracking Tracking is an important and widely-used application for wireless sensor networks Military to detect and track enemy troops and tanks Civilian life to track the movement of wild animals

13. SNEM - About target tracking (cont.) In target tracking applications the interesting events happen infrequently with long intervals of inactivity Most sensor nodes can go to sleep during the inactivity period only a small number of nodes stay alert to detect the presence of the target

14. SNEM SNEM is particularly designed for target tracking sensor networks The scheme lets most sensors go to sleep while only the sensors near the moving target keep active saves energy for sensor nodes while at the same time keeps tracking the moving target and sends the target information to the sink

15. SNEM (cont.) The network operations have two stages The watching stage no target is present in the field The tracking stage sensor nodes track the moving target

16. SNEM - Concepts Moving target Relay cell TN: Target Neighbor cell TN

17. SNEM - Details Each sensor node stores two state variables Cell status indicating the status of the cell Active time the time to keep the node active Relay Point (RP) the active node in a relay cell

18. SNEM - Details (cont.) Sleeping nodes periodically awake after every t a second depends on the size of the cell – a the maximum speed of the target - v t  a/v t

19. SNEM - Details (cont.) When the status of a cell changes from relay to TN the RP will periodically broadcast a cell status update message to all nodes in the cell for every t b seconds When a sleeping node awake it will keep active for t b seconds The broadcast will repeat for times

20. SNEM - Details (cont.) When the cell status becomes to relay nodes will broadcast a Relay Point (RP) message to other nodes in the same cell with a delay The remaining energy Random back off time

21. SNEM - Details (cont.) If the target moves very fast the Target Neighbor cells include the cells two step (or even several steps) Then the sensor sleep time t a can be set as 2a/v t

22. SNEM - Power balance When the current RP (say A) uses about 1/3 of its energy A will include its remaining energy and a retiring indication in a broadcast message when another node B is awake and finds out it has more remaining energy than A, it will send a take-over message to A

23. The Routing Protocol

24. Several routing protocols have been developed for sensor networks Directed Diffusion Leach Mesh  Do not work well with SNEM  only one node in each relay cell is active

25. The Routing Protocol (cont.) A routing protocol is needed jointly considers the node sleeping scheme in the application layer and data dissemination in network layer

26. The Routing Protocol (cont.) Routing cells cells are in the direction from source to destination

27. The Routing Protocol (cont.) A: source B: destination

28. The Routing Protocol (cont.) Contention-based mechanism with RTS/CTS is used in MAC layer Nodes in TN send a CTS packet with a delay

29. Performance Evaluation 1. Performance under Different Node Density 2. Different Source-Sink Distances 3. The Delay Performance 4. Resilience to Sensor Node Failures 5. Tracking Performance

30. Performance Evaluation - Parameters Simulator : QualNet The underlying MAC : 802.11 DCF Sinks : 4 Sensor Nodes : 900 Deployment : Random Area : 300m x 300m Simulation time : 600s Transmission range : 40m Sensing range : 20m Cells : 15 x 15 = 225 The probability of node failure : 0.1

31. Performance under Different Node Density - Delivery Ratio

32. Performance under Different Node Density - Energy Consumption

33. Different Source-Sink Distances - Delivery Ratio

34. Different Source-Sink Distances - Energy Consumption

35. The Delay Performance - Average delay

36. Resilience to Sensor Node Failures - Delivery ratio

37. Resilience to Sensor Node Failures - Energy consumption

38. Tracking Performance - Target tracking quality

39. Conclusions

40. Sensor Network Energy Management protocol (SNEM) is a novel energy management protocol for target tracking sensor networks exploits the features of target tracking applications and sensor networks allows sensor nodes that are far away from targets go to sleep save lots of energy while guarantee the accurate tracking and timely delivery Cell Relay routing protocol integrates very well with SNEM

41. Conclusions (cont.) SNEM scheme performs much better than another energy saving scheme – PEAS a popular routing protocol – Directed Diffusion SNEM saves significant amount of energy achieves high quality tracking and high delivery ratio

42. Question? Thank you.