The Problem of Location Determination and Tracking in Networked Systems

1
The Problem of Location Determination and
Tracking in Networked Systems

• Weikuan Yu, Hui Cao, and Vineet Mittal
• The Ohio State University

2
Outline

• The Problem Statement
• Applications
• Challenges
• Approaches

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The Problem Statement of Location Determination

• Devise a scheme that returns the location of the
  object
• Location
• Absolute location
• Relative location, e.g. beamforming, web-hosting
• Object
• Computing device, human, car, tank
• Information

4
The Problem Statement of Tracking

• Devise a scheme that tracks the location of an
  object
• Single object
• Multiple objects

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Applications

• Emergency services
• Efficient distribution of data
• Security
• Pursuer-evader

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Location and Tracking
Mobile Object
Static Object
Decision/Data Fusion
Physical Location
Symbolic Location
Location Service
Distributed
Centralized
Centralized
Distributed
Sensing
Beamforming
GPS
Node Location
Data Location
Non-infrastructure based
Infrastructure based
Infrastructure based
Non-infrastructure based
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Challenges

• Scalability
• Locating a mobile user in a large scale network
• Locating a node in a mobile ad hoc network
• Fault-tolerance
• Failure of a location server
• Sensor networks
• Limited energy
• Limited processing power
• Limited communication range
• Sensor coordination

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Sensor Networks

• Definition
• A spread network of small sensors
• Tracking moving objects
• Monitoring multiple objects
• Detecting low observable objects
• Sensor coordination
• Improved accuracy with aggregated information
• Reduced latency with informed selective
  coordination
• Minimize bandwidth consumption
• Mitigate the risk of node/link failures

9
Approaches

• Everything is related to everything else but
  near things are more related than distant things
• Online tracking of mobile users, by B. Awerbuch
  and D. Peleg
• Information utility
• Information driven dynamic sensor collaboration
  for target tracking, by F. Zhao, J. Shin, and J.
  Reich

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Online Tracking of Mobile Users

• Construction of a tracking structure
• Storing location information of users at select
  nodes in the system
• Access and Update Protocols
• Find using the stored information to locate the
  user
• Move updating of stored information on
  relocation of the user

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Information-Driven Sensor Coordination

• Making decision based on constraints regarding
  information, cost and resource.
• Metrics Information Utility
• A term that quantifies the content of some data
• An example of tracking

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Information-Driven Sensor Coordination
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Information Utility

• Information Driven Sensor Querying and Data
  Routing (IDSQ)
• M(p(XZ1, Z2, , Zj)) a U (p(XZ1, Z2, ,
  Zj-1, Zj)) (1-a) U(Zj)
• Information Utility
• Function U
• Based on information entropy, cost to obtaining
  new information and Belief state of posterior
  distribution

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Detection and tracking
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Decision fusion in collaborative sensor networks

• Collaborative signal processing tasks such as
  detection, classification, localization, tracking
  require aggregation of sensor data.
• Decision fusion allows each sensor to send
  quantized data (decision) to a fusion center.
• prevent overloading the wireless network
• conserve energy.
• Question What is optimal decision fusion?