Location Tracking in a Wireless Sensor Network by Mobile Agents and Its

Data Fusion Strategies Yu-Chee Tseng, Sheng-Po Kuo, Hung-Wei Lee and Chi-Fu Huang

The Computer Journal 2004Special Focus-Mobile and pervasive computing Volume 47, Issue 4, July 2004: pp. 448-460

Bao-Hua Yang

Outline

Introduction Network Model and Problem Statement The Location Tracking Protocol Fusion and Delivery of Tracking Results Prototyping Experiences and Simulation

Results Conclusion

Introduction

Many issues remain to be resolved for success of sensor network Scalability

Sensor network comprises a large number of nodes How to manage resources and information is not easy

Stability Be installed in outdoor or hostile environments Protocols should be stable and fault-tolerant

Power-saving Energy conservation should be kept in mind in all cases

Introduction

GoalLocation tracking: to monitor the roaming path

of a moving object An object is detected

A mobile agent will be initiated to track the roaming path

The agent will choose the sensor closest to the object to stay

Network Model and Problem Statement

Network Model and Problem Statement---Assumption

In order to track objects’ location, the sensor should know: Aware of its physical location Aware of the neighbor physical location The capability of compute and communication Sensing scope: R = the side length of the triangles

Object Assume that sensors can distinguish one object from

another

Network Model and Problem Statement

Working area: A0

Backup area:A1,A2,A3

The Location Tracking Protocol--- Basic idea

Master

Slave2 Slave1

The Location Tracking Protocol--- Basic idea

MasterSlave2

Slave1

The Location Tracking Protocol--- Basic idea

MasterSlave2

Slave1

The Location Tracking Protocol--- Basic idea

Master

Slave2 Slave1

The Location Tracking Protocol--- Protocol detail

•Status: Idle

Bid_master(ID,sig)

The Location Tracking Protocol--- Protocol detail

The Location Tracking Protocol--- Protocol detail

The Location Tracking Protocol--- Protocol detail

The Location Tracking Protocol--- Protocol detail

The Location Tracking Protocol--- Protocol detail

The Location Tracking Protocol--- Protocol detail

S0 S2

S1

The Location Tracking Protocol--- Protocol detail

(1):Master will revoke all slaves and invite two new one

(2):Master revoke slave S1 and invite a new one

(3):Master migrate itself to a sensor with strongest receive signals and revoke all slaves

slaveslave

Master

(4)

(5)

(6)

The Location Tracking Protocol--- Protocol detail

The Location Tracking Protocol--- Protocol detail

S0 S2

S1

The Location Tracking Protocol--- Protocol detail

S0 S2

S1

The Location Tracking Protocol--- Extension to irregular network topologies

The election process does not need to be changesSensors can still bid for serving as a

master/slave based on their signal strengths Only the rules to migrate masters/slaves

need to be modified

The Location Tracking Protocol--- Extension to irregular network topologies

Using Voronoi graphs to find the master and slaves

(b)The Voronoi graphs after removing the master

(c)The Voronoi graphs after removing the master and the first slave

(a)The Voronoi graphs of all vertics

The Location Tracking Protocol--- Extension to irregular network topologies

Working and backup areas

Backup area

Working area

Fusion and Delivery of Tracking Results Non-Agent-Based (NAB) strategy

Each sensor works independently and forward its sensing results back to the gateway

Threshold-Based (TB) strategy

Si Si+1

G

(1)The amount of result < Threshold carry(2)The amount of result > Threshold forward

1

12

Fusion and Delivery of Tracking Results Distance-Based (DB) strategy

The distance from the agent’s current and next sensors to the gateway are considered

Fusion and Delivery of Tracking Results G

iff C1 < C2 : the master agent will carry the results with itOtherwise: the results will be sent back to the gateway

Si Si+1

Si decides to carry the tracking result with it:

Si decides to deliver its current tracking result to the gateway:

1

12

Ni=

Prototyping Experiences and Simulation Results Simulation environment

Sensing field: 10000m*10000m Distance between two neighboring sensors:80mGateway is located at the center of the networkObject moves at a constant speed: 1~3mControl packet, location information, packet head

er: 2 bytes

Prototyping Experiences and Simulation Results

Experimental environment: (a) Triangular sensor network(b) Square sensor network

Prototyping Experiences and Simulation Results

Prototyping Experiences and Simulation Results

Prototyping Experiences and Simulation Results

Prototyping Experiences and Simulation Results

Prototyping Experiences and Simulation Results

Conclusion

Proposed a location-tracking protocol for regular and irregular sensor network Reducing communication and sensing

overhead