OPTIMIZING TREE RECONFIGURATION FOR MOBILE TARGET TRACKING IN SENSOR NETWORKS

Wensheng Zhang and Guohong Cao

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

root2. Collecting sensing data via the tree

Root receives reports and processes them3. 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

Energy consumption

E = Ed + Et (for each time interval) Ed : Data collection Et : Tree reconfiguration

Min-cost tree

Problem of Optimizing Tree Reconfiguration

Equal toFind a min-cost convoy tree sequence

Optimizing Tree Reconfiguration Schemes

A convoy tree is reconfigured in two steps1. The current root is replaced by a new

one2. The remaining part of the tree is

reconfigured to reduce the communication overhead

Root Replacement R predicts Lt+1 Replace R, if

DR, Lt+1 > dr

dr Large: high overhead on data collection Small: high overhead on tree

reconfiguration

How to determine dr?

How to determine dr? k(v) = dr / v

time units a target needs to travel through dr

Nodes send reports to Root on every time unit

The average energy consumption between two root replacement:

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.

OCR overhead analysis

Data collection energy:

Tree reconfiguration energy:

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.

OIR overhead analysis

OCR vs OIR

OCR:Higher priority on Data Collection OIR: Higher priority on Tree Reconfiguration

High target velocity, small sd/sc, small ds/d

ThanksQ&A