A Protocol for Tracking Mobile Targets using Sensor Networks

1. A Protocol for Tracking Mobile Targets using Sensor Networks H. Yang and B. Sikdar Proceedings of IEEE Workshop on Sensor Network Protocols and                 Applications , May 2003 Byun, Eun-kyu (ekbyun@camars.kaist.ac.kr)

2. Contents • Introduction • Challenges • A distributed algorithm for predictive tracking • Simulation result • Conclusion A protocol for tracking mobile targets using sensor network

3. Introduction • Tracking mobile target using sensor network • Scenario – military, civilian • Issues • Scalability • Minimize the power consumption • Distributed Predictive Tracking (DPT) algorithm • Scalability and Robustness • Using a cluster based architecture • Power conservation • Distributed mechanism for determining optimal set of sensors, others are in the hibernation mode • Predictive mechanism to intimate cluster heads about approaching target A protocol for tracking mobile targets using sensor network

4. Challenges • Scalable coordination • Size of the network, the number of targets and number of active queries • Tracking accuracy • Reduce likelihood of missing a target • Robust against node failure • Ad-hoc deployment • Computation and communication costs • Minimize communication requirement • Power constraint A protocol for tracking mobile targets using sensor network

5. Algorithm Overview • Distributed Predictive Tracking (DPT) algorithm • Does not require any central control point • Assumes cluster based architecture for sensor network • Ensure the sensor network’s scalability and energy efficiency • Sense – predict – communicate - sense • Distinguished role between border and inside sensors A protocol for tracking mobile targets using sensor network

6. Algorithm Assumption • Assumption of the DPT algorithm • All sensors are have the same characteristics • Sensors are uniformly distributed • Sensors have high beam, low beam mode • Sensors perform sensing according to its cluster head’s requirements • At lease 3 sensors to sense the target jointly • Sensor density satisfy that probability that at least 3 sensors can sensing target is more than 0.99 • Cluster head know location information of all sensors in cluster A protocol for tracking mobile targets using sensor network

7. Target Descriptor • Target descriptor formulation algorithm • Target Descriptor (TD) • Target identity • Target’s present location • Target’s next predicted location • Time stamp • Upstream cluster head(CHi) send TDito downstream cluster head(CHi+1) • Prediction mechanism • Predict next location based on pervious n-1 actual location • Accuracy VS overhead • Use linear predictor A protocol for tracking mobile targets using sensor network

8. Sensing • Sensor selection 1. Cluster head choose 3 sensors such that their distances to the predicted location are less than the sensor’s normal beam 2. Choose insufficient sensors using high beam distance 3. Asks its neighboring cluster heads for help • Wake up selected sensors • Collect information • Formulate TDi+1 A protocol for tracking mobile targets using sensor network

9. Failure Recovery • Failure scenario • Downstream Cluster head failure • Prediction failure • Recovery scheme • First level recovery • switch to high beam • Second level recovery • A group of sensors which are around r meters away from Li are activated • Nth level recovery • (2N-3)r meters away from Li are activated A protocol for tracking mobile targets using sensor network

10. Energy consideration • Energy saving strategies • Hibernation mode and prediction • Sensors use normal beam whenever possible • Communication cost of transmission of TD is insignificant • TD has to be sent to sink • The energy required for obtaining the TD for one location • Keep pmiss small enough A protocol for tracking mobile targets using sensor network

11. Simulation result • Simulation study concentrated on • The miss probability under different situation • The adaptability of the algorithm to target’s different speeds • Average energy consumed for tracking • Simulation setup • 600m X 600m 2-dim sensing area • Normal beam : 35m, high beam : 55m • The movement pattern : random waypoint model A protocol for tracking mobile targets using sensor network

12. Simulation result • Miss probability vs. Tracking resolution A protocol for tracking mobile targets using sensor network

13. Simulation result • Miss probability vs. sensing radius/moving speed A protocol for tracking mobile targets using sensor network

14. Simulation result • Energy consumption • 15m/s • 35m, 55m beam • Tracking resolution – 1s • 59 misses over 2000 point • E(Di)=43.93, Var(Di)=35.44 • Minimum – 6000 A protocol for tracking mobile targets using sensor network

15. Conclusion • Distributed Predictive Tracking algorithm • Prediction based on information of previous location • Totally distributed and scalable • Good performance at higher tracking resolution • Aimed at minimizing the energy consumption • Future Work • More complicated prediction algorithm • Interpolation mechanisms at cluster head when a sensors reports multiple target simultaneously • Consider mobile sensors • Drawback • Energy consumption of border sensors • Not good at very fast target • Assuming Uniform distribution A protocol for tracking mobile targets using sensor network