1. 1 VISA: Virtual Scanning Algorithm for Dynamic Protection of Road Networks IEEE Infocom’09, Rio de Janeiro, Brazil Jaehoon Jeong (Paul), Yu Gu, Tian He and David Du Computer Science and Engineering University of Minnesota {jjeong,yugu,tianhe,du}@cs.umn.edu April 23rd, 2009

2. Problem Definition 2 Entrance pointProtection point Detect Take action Wireless Sensor Deployment

3. Virtual Scan vs. Legacy Schemes 3 2130 Detect! 2130 (a) Always-Awake (b) Duty Cycling (c) Virtual Scan Sensor network sleeps during the silent time (i.e., sleeping time). Each sensor sleeps during the scan time and the silent time. Sensor network is always awake. l Entrance PointProtection Point Sleeping Time

4. VISA Scheduling Procedure 4 Road Network Graph Sensor Deployment Working Schedule Sleeping Schedule Wireless Sensor Network

5. Road Network Graph 5 The vertices in G are intersections, protection points, and entrance points.

6. Working Schedule Establishment 6  Working Schedule during the Scan Period  When each sensor wakes up and how long it works for sensing. Working Schedule = (work start time, work end time)  Working Schedule Setup  Each sensor’s work start time is set to the scan arrival time.

7. Sleeping Schedule Establishment 7  Sleeping Schedule  How long all the sensors can sleep with detection guarantee.  One global sleeping time is computed using the Shortest Path. Maximize the sum of scan time and silent time. Entrance Points Protection Points How often to generate the Virtual Scan on Road Network? 2130 Sleeping Time Objective

8. Sleeping Schedule Establishment 8 Maximum sum of scan time and silent time for detection guarantee. This formulation guarantees the target detection. the shortest path When the scan arrives at e1, the path of (e1,p2) is vulnerable to the intrusion.

9. Handling Sensing Holes 9  Two Cases for Sensing Holes  Deployment Time  Sensor Energy Depletion  Our Approach Labeling into E or P Linear Network

10. Hole Labeling in Linear Network 10 How to label two sensing holes? Case 1:Case 2: Case 3:Case 4: The Shortest Path for Sleeping Time The Maximum Shortest Path (i.e., Maximum Sleeping Time) The Sleeping Time is the same as with Case 1 The Sleeping Time longer than Case 1 and Case 2

11. Minimum Spanning Tree (MST) based Clustering for Hole Labeling 11 The idea is to maximize the inter-distance between Entrance Cluster (E) and Protection Cluster (P). Maximum Inter-distance This maximum inter-distance determines the sleeping time.

12. Performance Evaluation 12  Performance Metrics  Network Lifetime  Average Detection Time  System Behavior  Sleeping Time over System Lifetime  Investigated Parameters  Working Time  Sensor Density  Silent Time Road Network for Simulation

13. Comparison of Sleeping Time of Three Approaches over System Lifetime 13 System Lifetime Comparison Virtual Scan: 28.2 hours Duty Cycling: 1.4 hours Always-Awake: 5.4 minutes

14. Impact of Working Time 14 (a) Network Lifetime for Working Time (b) Average Detection Time for Working Time 1. Network Lifetime Comparison for 1-second Working Time  Virtual Scan’s lifetime is18 times longer than Duty Cycling’s. 2. Average Detection Time Comparison for 1-second Working Time  Virtual Scan’s ADT is 2 times longer than Duty Cycling’s.

15. Conclusion 15  In the surveillance for road networks, the scan-based sensing algorithm (VISA) opens a promising direction.  VISA takes advantages of road network’s characteristics for a maximum sleeping time. Vehicles move along the roadways whose maps are available.  Contributions  Energy-efficient Sensing Schedule for Road Networks VISA uses the optimal sleeping time for an arbitrary road network.  Sensing Hole Handling VISA guarantees target detection while sensor network deteriorates.  Basis for Quality of Surveillance VISA can control the trade-off between the network lifetime and average detection time.