GRAIL: Experiences Using a General Purpose Wireless Device Positioning

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GRAIL Experiences Using a General Purpose
Wireless Device Positioning

• Presented by Richard Martin
• Joint work with David Madigan, Eiman Elnahrawy,
• Pervasive Workshop, Oct. 2007

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Wireless Explosion

• Technology trends creating cheap wireless
  communication in every computing device
• Radio offers localization opportunity in 2D and
  3D
• New capability compared to traditional
  communication networks
• 4 technology communities
• WLAN (802.11x)
• Sensor networks (802.15.4)
• Cell carriers(3G)
• Active RFID

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Challenge and Opportunity

• General purpose localization analogous to general
  purpose communication!
• Work on any device with little/no modification
• Supports vast range of performance
• Will drive new applications
• Challenge Can we localize all device radios
  using only the communication infrastructure?
• How much existing infrastructure can we leverage?
  
• 1st Application Search
• General purpose communication needed for global
  search
• Can we make finding objects in the physical space
  as easy as Google ?

4
Vision to reality

• Getting closer
• This talk
• Experiences with running an actual localization
  system for last 5 months

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GRAIL

• General-Purpose
• Support wide range of technologies and modalities
• Real-time
• Adaptable
• Support dynamic feedback from changing radio
  environment
• Indoor
• Outdoor use GPS
• Localization

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GRAIL Approach
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Typical results

• LCD projector with imbedded pipsqueak active RFID
  tag, Core 2

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Lessons

• Incorporating new technologies successful
• Wifi, roll-call/pipsqueak, motes
• Easy to detect motion
• Signal strength stable at a given spot
• Limitations using signal strength
• Average error 15 ft
• Worse case error 60 feet
• Worse case is very bad for real applications

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Future Directions

• Improve worst case accuracy
• High density landmarks/readers (100)
• High frequency clocks and time-of-arrival\
• Careful and dense signal strength maps discounted
• High human costs, error prone, drift with time
• Building higher-level services
• Person location web-site (A-list)
• Inventory control (with LCSR)
• Incorporate privacy mechanisms
• Drop data at landmarks, server, database
• Anonymize

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Demo

• In Core 340 during the poster session
• Watch the system track a laptop.
• hide and seek with a laptop.