Young-sam Kim / M.D Course School of Information Technology

Dept. of Computer Engineering Korea University of Technology and Education

Location Tracking in a WSNby Mobile Agents and

Its Data Fusion StrategiesYu-Chee Tseng, Sheng-Po Kuo, Hung-Wei Lee, and Chi-Fu

Huang

Contents

Abstract

Introduction

Network Model & Problem Statement

The Location Tracking Protocol

Fusion & Delivery of Tracking Results

Prototyping Experiences and Simulation Results

Conclusion

Q/A

- Abstract -

Abstract (1)

Providing ubiquitous sensing, computing and

communication capability -> greatly facilitate human life

1. WSN (Wireless Sensor Network)

2. Location Tracking (1)

One of the central issues in sensor networks.

To monitor the roaming path of a moving object.

Abstract (2)

Similar to the location-update problem in PCS networks.

Location Tracking is more challenging in two senses.

1) Central control mechanism & backbone network. (X)

2) Wireless communication bandwidth is very limited.

3. Location Tracking (2)

4. Proposed paradigm

Novel protocol based on the mobile agent paradigm.

The communication & sensing overheads are greatly

reduced.

Based on IEEE 802.11b, NICs

- Introduction -

WSN (1)

Rapid progress

Wireless communication

MEMS technologies

Wireless Sensor Network

Inexpensive node

collecting

processing

storing

Environmental Info

WSN (2)

1. Sensor are connected

Past : wire lines.

Today : wire lines + wireless ad hoc network

1) The flexibility of installation & configuration is greatly improved.

2) Research activities have recently been commenced in SN

WSN (3)

2. Issues remain to be resolved

Scalability

- coverage and exposure problems

Stability

- stable and fault-tolerant

Power-saving

- since no plug-in power is available

- energy consumption of communications might be a major factor

- mobile agent-based solutions are sometimes more power-

efficient

Proposed paradigm

3. Novel protocol based on the mobile agent paradigm To solve the location tracking problem

Advantage

1) sensing, computing & communication overheads can be greatly

reduced. -> delivery & fusion of the tracking results

2) on-site or follow-me services may be provided

Network Model & Problem Statement

Network Model (1)

Sensor network (2D) Triangular network (regular)

Network Model (2) & Problem Statement

Sensing scope is r Working Area is A0, Backup Area is A1, A2, A3

Practice errors may exist, and thus more sensors will be needed to improve the accuracy.

The Location Tracking Protocol

Basic Idea

Proposed protocol is derived by the cooperation of sensors. (master 1, slave 2)

Protocol Details (1)

Assume that … 1) Sensors can distinguish one object from the other 2) Each object periodically send a unique ID 3) focus on only one particular object

Protocol Details (2)

Master agent : closets to the object - go to master state & protocol

Slave agents : nearby sensors - go to slave state & protocol

Once the object enters the backup areas, the roles of master & slave may be changed

Protocol Details (3)

Master

For track1, the master discovers two slaves losing the target simultaneously.

For track2, only the slave agent in S1 will be revoked, and new one will be invited.

For track3, the master discovers one slave as well as itself losing the target

Protocol Details (4)

Each sensor will keep an object list (OL). unique identity, denote by ID, two sub-field

Two sub-field : status & time-stamp 1) ID.state : Master, Slave, Standby, Inhibited

2) time-stamp is the time when the record is last updated.

Protocol Details (5)

Seven types of control messages 1) bid-master(ID, sig) 2) assign_slave(ID, si, t) 3) revoke_slave(si) 4) inhibit(ID) 5) release(ID) 6) move_master(ID, si, hist) 7) data(ID, sig, ts)

Basic Protocol

Election Protocol

Master Protocol

Slave Protocol

Extension to Irregular Network Topologies

The election process does not need to be changed.

The rules to migrate masters/slaves need to be modified.

Sensors need to know the locations of at least their two-hop neighbors.

Still use one master and two slaves to track an object.

Extension to Irregular Network Topologies

How to define the master & slaves ? The problem can be solved by a divide-and-

conquer solution in time complexity

Fusion & Delivery of Tracking Results

Fusion & Delivery of Tracking Results (1)

Assume that…

one of the sensors in the network serves as the

gateway connecting to a location server in the

wireline network.

Fusion & Delivery of Tracking Results (2)

Propose three data delivery solutions. 1) Non-Agent-Based (NAB) strategy. Each sensor works independently and forwards its

sensing results back to the gateway

2) Threshold-Based (TB) strategy. 3) Distance-Based (DB) strategy. The delivery action may be taken only when the

master agent moves.

Prototyping Experiences

Prototyping Experiences

IEEE 802.11b NICs

Object

Sensor 1

Sensor 0

Sensor 2

Prototyping Experiences

Prototyping Experiences

Position approximation algorithm

Prototyping Experiences

Prototyping Experiences

Prototyping Experiences

Prototyping Experiences

Simulation Results

Simulation Results (1)

Simulation Results (2)

Conclusions

Conclusion

A mobile-agent approach, A data fusion

model and several data delivery strategies

are significantly reducing the

communication & sensing overheads.

Q/A

Thank you