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Location System for Ubiquitous Computing

Location System for Ubiquitous Computing. Jeffrey Hightower Gaetano Borriello University of Washington. Location. Location is a useful contextual information Physical versus Symbolic Absolute versus relative. Location (cont.). Physical versus Symbolic Physical : (45 。 N, 145 。 W)

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Location System for Ubiquitous Computing

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  1. Location System for Ubiquitous Computing Jeffrey Hightower Gaetano Borriello University of Washington

  2. Location • Location is a useful contextual information • Physical versus Symbolic • Absolute versus relative

  3. Location (cont.) • Physical versus Symbolic • Physical : (45。N, 145。W) • Symbolic : in the kitchen, next to a mailbox • Application can determine symbolic location resolution according to the physical location (resolution is important!!)

  4. Location (cont.) • Absolute versus relative • Absolute : shared reference, e.g. latitude • Relative : each object have its own reference or frame • Transfer relative to absolute location • Use triangulation with multiple relative position • Inverse • trivial…

  5. Location System • To locate people, equipment and other tangibles by one or more location-sensing techniques • location-sensing techniques • Triangulation : lateration, angulation • Proximity • Scene analysis

  6. Issue about location system • Accuracy and precision • Accuracy : the grain size of the location system can provide (distance) • Precision : the probability that we can get that accuracy (percentage) • Error distribution along with the density of sensor

  7. Issue about location system • Scale • Evaluate by the coverage area and number of object can locate per unit infrastructure per time interval • Time is a important consideration • Bandwidth • Accuracy

  8. Issue about location system • Limitation • GPS doesn’t work well inside the building • Some tagging systems can read tags properly only when a single tag is present. • Privacy • Cost • Time cost • Space cost • price

  9. A survey of location system • Active badge • Active Bat • Cricket • RADAR • MotionStar magnetic tracker • Easy living • Smart floor • E911 • …

  10. Future work • Lower cost, less amount of infrastructure, better power consumption, etc… • Sensor fusion • Ad hoc location sensing

  11. Sensor fusion • The use of multiple technologies or location systems simultaneously to form hierarchical and overlapping levels of sensing. • Increase accuracy and precision beyond individual system

  12. Ad hoc location sensing • This approach borrows the idea from the ad hoc networking research • Cooperate with other nearby objects by sharing sensor data to factor out overall measurement error.

  13. Ad hoc location sensing • The SpotON system implements ad hoc location sensing • Using low cost tag • Radio signal attenuation to estimate intertag distance • Exploit the density of tags

  14. Q&A

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