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Towards Mobile Phone Localization without War-Driving Ionut Constandache

Towards Mobile Phone Localization without War-Driving Ionut Constandache Co-authors: Romit Roy Choudhury and Injong Rhee. Context. Pervasive wireless connectivity + Localization technology =. Location-based applications (LBAs). Context. Pervasive wireless connectivity +

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Towards Mobile Phone Localization without War-Driving Ionut Constandache

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  1. Towards Mobile Phone Localization without War-Driving Ionut Constandache Co-authors: Romit Roy Choudhury and Injong Rhee

  2. Context Pervasive wireless connectivity + Localization technology = Location-based applications (LBAs)

  3. Context Pervasive wireless connectivity + Localization technology = Location-based applications (LBAs) (iPhoneAppStore: 6000 LBAs, Android: 1000 LBAs)

  4. Location-Based Applications (LBAs) • Examples: Location-based recommendations, geo-tagging GeoLife: shopping list when near a grocery store TrafficSense: real-time traffic conditions

  5. Localization Technology • LBAs executed on mobile phones AccuracyTechnologyEnergy-Efficiency 10m GPS 4h-8h 20-40m WiFi / Skyhook 16h 200-400m GSM ~days

  6. Localization Technology • LBAs executed on mobile phones AccuracyTechnologyEnergy-Efficiency 10m GPS 4h-8h 20-40m WiFi / Skyhook 16h 200-400m GSM ~days Best Scenario: Accurate and Energy-Efficient Localization

  7. Localization Technology • LBAs executed on mobile phones AccuracyTechnologyEnergy-Efficiency 10m GPS 4h-8h 20-40m WiFi / Skyhook 16h 200-400m GSM ~days

  8. WiFi / Skyhook Localization • Basic Idea: • Several trucks war-drive a place • Create Radio map = <Location: WiFiAPs> • Distribute map to phones • Phone user goes to war-driven region, overhears WiFiAPs • Reverse Look Up WIFI APs against radio map • Obtains location

  9. Is Skyhook the solution? Middle Ground (Lower Accuracy than GPS, Longer Battery lifetime) (Better Accuracy than GSM, Shorter Battery lifetime)

  10. Is Skyhook the solution? Middle Ground (Lower Accuracy than GPS, Longer Battery lifetime) (Better Accuracy than GSM, Shorter Battery lifetime) but …

  11. Is Skyhook the solution? Middle Ground (Lower Accuracy than GPS, Longer Battery lifetime) (Better Accuracy than GSM, Shorter Battery lifetime) but … At the cost of: • Degraded location accuracy: walking paths ~ 60m • Reliance on infrastructure (APs) • War-driving ($$ + carbon footprint) “NYTimes: Skyhook fleet 500 trucks/drivers”

  12. Visual Representation Of the State of the Art (Duke Campus)

  13. No Eng. Eff. & Acc. Solution Skyhook Better than GPS Eng. Eff. SkyHook GPS unusable with phone battery GSM too inaccurate

  14. Eng. Eff. & Acc. Solution CompAcc GPS unusable with phone battery GSM too inaccurate GPS unusable with phone battery

  15. Contents • CompAcc • Evaluation • Limitations and Future Work • Conclusion

  16. Contents • CompAcc • Evaluation • Limitations and Future Work • Conclusion

  17. Goals • No War-Driving • Cannot drive walking paths (campus, parks, …) • Expensive / Environment unfriendly • No reliance on WiFi infrastructure • Scale to rural regions / developing countries • Good accuracy (~ GPS) • Improved energy-efficiency • Better than Skyhook, GPS

  18. CompAcc: Basic Idea • Initial GPS puts user at known location on path GPS

  19. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail Directional Trail

  20. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail Directional Trail <Step, Direction>

  21. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail • Compass direction noisy => User’s Location Drifts Directional Trail

  22. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail • Compass direction noisy => User’s Location Drifts Directional Trail

  23. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail • Compass direction noisy => User’s Location Drifts • Assume user follows the paths in her vicinity Directional Trail

  24. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail • Compass direction noisy => User’s Location Drifts • Assume user follows the paths in her vicinity • Compute path signatures • Derived from a local electronic map (Google Maps) Path Signature Directional Trail …

  25. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail • Compare directional trail with path signatures • Best match corrects direction Path Signature Directional Trail …

  26. CompAcc: Basic Idea • Direction(compass) + Displacement(accelerometer) = Directional Trail • Compare directional trail with path signatures • Best match corrects direction Path Signature Directional Trail …

  27. Turns correct displacement … Path Signature Directional Trail

  28. Turns correct displacement … Path Signature Directional Trail

  29. Turns correct displacement … Path Signature … Path Signature Directional Trail Directional Trail

  30. Turns correct displacement … Path Signature Corrected Location … Path Signature Directional Trail Directional Trail

  31. Advantages • No war-driving / No WiFi infrastructure • Maps available ubiquitously • Improves battery lifetime

  32. Directional Trail: displacement • Accelerometer based step count • displacement = step_count * step_size

  33. Directional Trail: direction

  34. Path Signature • Extract from Google Maps • Geodesic formulas

  35. Matching Directional Trail with Path Signatures Path Signature Directional Trail Dissimilarity Metric: ci = compass readings pi = path computed direction N = directional trail size

  36. Contents • CompAcc • Evaluation • Limitations and Future Work • Conclusion

  37. Results • Compared 3 localization schemes • CompAcc • Skyhook • Wifi-War-Walk (We war-droved walking paths in campus) • Metrics Instantaneous Error = distance(estimated, real) Average Localization Error (ALE) = Average Instantaneous Error

  38. CompAcc Instantaneous Error

  39. CompAcc Instantaneous Error

  40. Results

  41. Results

  42. Results Average ALE GPS: 10m CompAcc: 11m WiFi-War-Walk: 30m Skyhook: 70m Energy GPS: 10h CompAcc: 23h WiFi-War-Walk:16h Skyhook:16h

  43. Skyhook CompAcc g – GPS s – Skyhook c - CompAcc Assume GPS is absolute truth Assume GPS is absolute truth

  44. Contents • CompAcc • Evaluation • Limitations and Future Work • Conclusion

  45. Limitations and Future Work • Map Generation • Manually mark footpaths • User Position Estimated along the Path • Apply particle filters to accommodate wide roads • Multiplexing between Localization Methods • Hand-off to Skyhook/GPS when driving • Extend to vehicular movement

  46. Contents • CompAcc • Evaluation • Limitations and Future Work • Conclusion

  47. CompAcc • Today’s localization technologies limited • Energy- Efficiency • Coverage/Accuracy • Rely on simple localization mechanism • Need: Compass, Accelerometer and Maps • Evaluation results: • ALE: 11m • Battery: 23h • CompAcc scales to any mapped region of the world

  48. Questions? Thank You! Visit the SyNRG research group @ http://synrg.ee.duke.edu/

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