1. A Moving Strategy for Mobile Sink in Secure Data Collection Zhou Sha

2. Motivation The advantages of mobility: hotspot, latency The compromise potential of mobility: tracking, traffic analysis Traffic analysis -> reduce traffic Tracking -> reduce sojourn time of mobile sink in the field A moving strategy

3. Outline Motivation Network Model & Problem Definition Our Solution – The moving strategy – The shortest-path-like routing protocol Performance Evaluation

4. Network Model A large number of static nodes & a mobile sink node The mobile sink node traverses through the field to collect data. Mobility limitation: a monotonically increasing curve Routing protocol: a shortest-path-like routing protocol

5. Network Model (cont.) Criterion: the summation of least hop count of all static nodes.

6. The moving strategy A greed algorithm: find a local optimal moving direction. Set up a coordinate system – Moving quadrant: IV – Candidate nodes quadrant: I, III, IV (out of the transmission of mobile sink) – the routing path length (in hops) l from S to B is approximately linear to d,

7. The moving strategy (cont.) The problem is converted to: (1) Subject to: (2) First differentiation: (3) is the norm of

8. The moving strategy (cont.) Three stationary point: (R, 0), (0, R) and Minimum extremum: – (R, 0), (0, R) for the static nodes in quadrant I and III – for the static nodes in quadrant IV

9. The routing protocol A shortest-path-like routing protocol Every static nodes gets least hop count

10. Performance Evaluation Experiment setup Different deployment: uniformly or asymmetrically Three comparing moving strategy: random walk, diagonal moving and moving peripherally The size of the field (m)200 X 200 The number of the static nodes100, 150, 200, 250, 300 The transmission radius of the static node (m) 25 The number of the mobile sink node1 The transmission radius of the mobile sink node (m) 25 The move distance of the mobile sink node (m) 25

11. Performance Evaluation

12. Thanks