1. Wensheng Zhang and Guohong Cao

2. Dynamic Convoy Tree-based Collaboration (DCTC) 1. Constructing the Initial Convoy Tree  Apply existing root election algorithm  Other node connect to a neighbor closest to the root 2. Collecting sensing data via the tree  Root receives reports and processes them 3. Tree expansion and pruning  Apply existing prediction schemes to involve new nodes  Prune useless nodes (too far from the target)  Change the root node  The root node makes all decisions

4. Energy consumption  E = E d + E t (for each time interval)  E d : Data collection  E t : Tree reconfiguration  Min-cost tree Problem of Optimizing Tree Reconfiguration Equal to Find a min-cost convoy tree sequence

5. Optimizing Tree Reconfiguration Schemes  A convoy tree is reconfigured in two steps 1. The current root is replaced by a new one 2. The remaining part of the tree is reconfigured to reduce the communication overhead

6. Root Replacement  R predicts L t+1  Replace R, if D R, Lt+1 > d r  d r  Large: high overhead on data collection  Small: high overhead on tree reconfiguration  How to determine d r ?

7.  k(v) = d r / v  time units a target needs to travel through d r  Nodes send reports to Root on every time unit  The average energy consumption between two root replacement:

8. Optimized Complete Reconfiguration (OCR)  The current root decides and initiates root replacement  New root notifies all nodes this change.  Reconfigure the tree: Each node connects to the neighbor closest to the new root node.

9. OCR overhead analysis  Data collection energy:  Tree reconfiguration energy:

11. Optimized Interception-based Reconfiguration (OIR)  The current root decides and initiates root replacement  New root notifies all nodes this change.  Reconfigure the tree: Each node checks whether it needs to change its parent node.

13. OIR overhead analysis

14. OCR vs OIR  OCR:Higher priority on Data Collection  OIR: Higher priority on Tree Reconfiguration  High target velocity, small s d /s c, small d s /d

15. ThanksQ&A