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

1
Location Tracking in a Wireless Sensor Network by
Mobile Agents and Its Data Fusion Strategies

• accepted by The Computer Journal (SCI)
• Y.-C. Tseng, S.-P. Kuo, H.-W. Lee, and
• C.-F Huang

Presented by Chih-Chieh Hung Feb.25.2004
2
Outline

• Introduction
• Problem Statement
• The Location Protocol
• Conclusions

3
Introduction

• Wireless sensor network
• consists of many inexpensive wireless nodes
• Ad hoc networking technology facilitates
  inter-sensor communication.
• Location-based services can be combined with
  sensor networks.

Wow! Good service!
Service
Service
Service
4
Issue remain to be resolved

• Scalability
• It is not an easy job to manage a large number of
  nodes.
• Stability
• Protocols should be stable and fault-tolerant.
• Power-saving
• Sensor devices will be operated by battery powers.

5
Location Tracking problem

• Location-Tracking problem
• Determine the roaming path of a moving object
  in the sensor network.
• Challenges
• Therere no central control mechanism and
  backbone network in such environment.
• The wireless communication bandwidth is very
  limited

6
Mobile agent paradigm

• Properties
• Once a new object is detected, the mobile agent
  will be initialed to track the roaming path.
• The agent is mobile since it will choose the
  sensor closest to the object to stay.
• Advantages
• Sensing, computing, and communication overheads
  can be greatly reduced.
• Context-aware services may be provides by mobile
  agents.

7
Problem Statement

• Location-Tracking problem
• Determine the roaming path of a moving object
  in the sensor network.
• Sensor Capabilities
• Aware of its location and its neighbors
• Aware of distance between itself and the object
• Computing
• Communication

8
Network Model

• Definition Sensing scope
• The diameter of the range that the sensor can
  detect the object.
• Network Models

I am a sensor
r
Triangular
Irregular
9
Positioning

• Assumption
• 3 sensors are sufficient to determine the
  location of object.
• An Example

10
Positioning (contd)

• Definition Working Area, Backup Area

Working Area
Backup Area
11
The Location Tracking Protocol

• Basic Idea
• cooperation of sensors
• Master Mobile Agent
• Slave Slave Agent
• Operations
• Master
• Dispatch
• Migrate
• Slave
• Be Revoked
• Be Reassigned

12
State Transition diagram of a sensor
out of sensing range
Master
Master move in
Bid Winner
Detect a new target
Idle
Election
Bid loser
Invited to be a slave
out of sensing range
Slave
13
Possible roaming tracks for an object to leave a
triangle
Revoke all slaves invite new slaves
Revoke a new slave
Master migrate revoke all slave
14
An Example for The Cooperation of Masters Slaves
S2
S1
A0
F0
A1
S6
F1
S0
E0
Next Slide Please
S5
15
An Example for The Cooperation of Masters Slaves
bye
S5
G1
16
Inhibiting Father Sensor from Monitoring The
Object
S9
S8
S10
Well-done
S2
S1
S11
S7
S3
S0
S6
S5
S4
17
Extension to Irregular Network Topologies

• Definition Working Area, Backup Area

Working Area
Backup Area
18
Voronoi Grpah

• Definition Voronoi graph

V points
Voronoi Graph
19
Define the master and two slaves

• Step1
• construct Voronoi grpah
• Master (m)
• the sensor of the segment containing the
  object
• Step2
• reconstruct Voronoi grpah on V-m
• 1st slave (S1)
• the sensor of the segment containing the
  object
• Step3
• reconstruct Voronoi grpah on V-m, S1
• 2rd slave (S2)
• the sensor of the segment containing the
  object

20
An Example
S2
m
S1
21
An Example (contd)
S2
m
S1
22
An Example (contd)
S2
m
S1
23
Conclusion

• This paper proposed a novel location-tracking
  protocol for regular and irregular sensor
  networks.
• A mobile-agent approach is adopted, which enables
  agents to roam around to follow the moving
  object, hence significantly reducing the
  communication and sensing overheads.
• The design of protocol is easy and reasonable in
  such a environment.