An overview of Positioning Technologies

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An overview of PositioningTechnologies

• - For beginners-

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Contents

• Why location-based computing
• Brief comparison between different positioning
  technologies
• Summary

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Why location-based computing

• Because Mark Weiser wanted it
• To provide Context-rich services

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Active Badges

• Transmits a unique infra-red signal every 10
  seconds
• Central server collects signal through fixed
  sensors and provides API for using the data
• Has limited effective range of several meters
• Direct sunlight may hinder it from working
  properly

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Active Bats

• Uses an ultrasonic pulseinstead of Infrared
• Bat emits ultrasonic pulse whenrequested and
  time-of-flightof the ultrasonic pulses
  toreceivers are calculated
• 95 of the sensor readings being correct to
  within 3cm in 3D
• Has very weak scalability

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Cricket

• Similar to Active Bat but beacons are on the wall
  and listeners are attached to handheld devices
• Beacon periodically broadcasts its space
  identifier and position coordinates on a RF
  channel
• Receivers can ignore ultrasonic pulses after the
  end of RF packets
• Decentralized computation

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RADAR

• Measures the signal strength and SNR of signal to
  compute 2D position
• Can be implemented in two ways scene-analysis
  and signal-strength lateration
• Based on WaveLan wireless networking- No
  additional investment is needed- Hard to
  calculate positions in 3D
• May have to rebuild signal-strength database if
  environment changes

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Comparison 1
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Easy Living

• Use computer visions to figureout where things
  are
• Background subtraction and person detection

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GPS

• GPS - start takes several minutes to get a
  fix- Receivers require line of sight
• A-GPS- Network-assisted GPS- Reduces GPS search
  time- Allows use of weaker signals than
  on-assisted GPS

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Smart Floor

• Embedded pressuresensors capture foot-steps and
  the data isused for positiontracking
• Poor scalability and high cost to implement

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MotionStar

• Used in motion capture forcomputer animation
• Generate axial DC magneticfield pulse from
  antennas
• Position is calculated by measuringresponse in
  three orthogonal axes to the transmitted field
  pulse

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E911

• Enhanced Observed time difference- Requires
  measure- ments from 3 BS- Position is
  determined by comparing the time differences
  between two sets of timing measurements.-
  Similar to TOA

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RFID

• Reader produces low level radiofrequency
  magnetic field whichacts as a carrier of power
• Antenna in RFID tag gatherenergies from magnetic
  field topower embedded IC and send predefined
  data to reader

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Comparison 2
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Summary

• Each technologies have their own strong and weak
  points, so think enough before choosing any
  technology
• Integrating different technology can yield good
  result (accuracy/reliability)

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Thank you for yourattention.