1. Mobile and Pervasive Computing - 4 Location in Pervasive Computing Presented by: Dr. Adeel Akram University of Engineering and Technology, Taxila,Pakistan http://web.uettaxila.edu.pk/CMS/AUT2015/teMPCms Shwetak N. Patel, University of Washington http://shwetak.com

2. Outline  Defining location  Methods for determining location  Ex. Triangulation, trilateration, etc.  Location Systems  Challenges and Design Decisions  Considerations

3. 3 Location  A form of contextual information  Person’s physical position  Location of a device  Device is a proxy of a person’s location  Used to help derive activity information

4. 4 Location Tracking

5. 5 Representing Location Information  Absolute  Geographic coordinates (Lat: 33.98333, Long: -86.22444)  Relative  1 block north of the main building  Symbolic  High-level description  Home, bedroom, work

6. 6 No one size fits all!  Accurate  Low-cost  Easy-to-deploy  Ubiquitous  Application needs determine technology

7. 7 Consider for example…  Motion capture  Car navigation system  Finding a lost object  Weather information  Printing a document

8. Others aspects of location information  Indoor vs. outdoor  Absolute vs. relative  Representation of uncertainty  Privacy model 8

9. Lots of technologies! 9 Ultrasonic time of flight E-911 Stereo camera Ad hoc signal strength GPS Physical contact WiFi Beacons Infrared proximity Laser range-finding VHF Omni Ranging Array microphone Floor pressure Ultrasound

10. 10 Some outdoor applications Car Navigation Child tracking Bus view E-911

11. 11 Some indoor applications Elder care

12. Outline  Defining location  Methods for determining location  Ex. Triangulation, trilateration, etc.  Systems  Challenges and Design Decisions  Considerations

13. 13 Approaches for determining location  Localization algorithms  Proximity  Lateration  Hyperbolic Lateration  Angulation  Fingerprinting  Distance estimates  Time of Flight  Signal Strength Attenuation

14. 14 Proximity  Simplest positioning technique  Closeness to a reference point  Based on loudness, physical contact, etc.

15. 15 Lateration  Measure distance between device and reference points  3 reference points needed for 2D and 4 for 3D

16. 16 Hyperbolic Lateration  Time difference of arrival (TDOA)  Signal restricted to a hyperbola

17. 17 Angulation  Angle of the signals  Directional antennas are usually needed

18. 18 Determining Distance  Time of flight  Speed of light or sound  Signal strength  Known drop off characteristics 1/r^2-1/r^6  Problems: Multipath

19. 19 Fingerprinting  Mapping solution  Address problems with multipath  Better than modeling complex RF propagation pattern

20. 20 Fingerprinting SSID (Name)BSSID (MAC address)Signal Strength (RSSI) linksys00:0F:66:2A:61:0018 starbucks00:0F:C8:00:15:1315 newark wifi00:06:25:98:7A:0C23

21. 21 Fingerprinting  Easier than modeling  Requires a dense site survey  Usually better for symbolic localization  Spatial differentiability  Temporal stability

22. 22 Reporting Error  Precision vs. Accuracy

23. 23 Reporting Error  Cumulative distribution function (CDF)  Absolute location tracking systems  Accuracy value and/or confusion matrix  Symbolic systems

24. Outline  Defining location  Methods for determining location  Ex. Triangulation, trilateration, etc.  Location Systems  Challenges and Design Decisions  Considerations

25. 25 Location Systems  Distinguished by their underlying signaling system  IR, RF, Ultrasonic, Vision, Audio, etc

26. 26 GPS  Use 24 satellites  TDOA  Hyperbolic lateration  Civilian GPS  L1 (1575 MHZ)  10 meter acc.

27. 27 Active Badge  IR-based  Proximity

28. 28 Active Bat  Ultrasonic  Time of flight of ultrasonic pings  3cm resolution

29. 29 Cricket  Similar to Active Bat  Decentralized compared to Active Bat

30. 30 Cricket vs Active Bat  Privacy preserving  Scaling  Client costs Active Bat Cricket

31. 31 Ubisense  Ultra-wideband (UWB) 6-8 GHz  Time Difference Of Arrival (TDOA) and Angle Of Arrival (AOA)  15-30 cm

32. 32 RADAR  WiFi-based localization  Reduce need for new infrastructure  Fingerprinting

33. 33 Place Lab  “Beacons in the wild”  WiFi, Bluetooth, GSM, etc  Community authored databases  API for a variety of platforms  RightSPOT (MSR) – FM towers  http://msr-waypoint.com/en- us/um/people/jckrumm/Publications%202003/rightSPOT%20publish.pdf http://msr-waypoint.com/en- us/um/people/jckrumm/Publications%202003/rightSPOT%20publish.pdf http://research.microsoft.com/apps/pubs/default.aspx?id=64611

34. 34 ROSUM  Digital TV signals  Much stronger signals, well-placed cell towers, coverage over large range  Requires TV signal receiver in each device  Trilateration, 10-20m (worse where there are fewer transmitters)

35. 35 Comparing Approaches  Many types of solutions (both research and commercial)  Install custom beacons in the environment  Ultra-wideband (Ubisense), Ultrasonic (MIT Cricket, Active Bat), Bluetooth  Use existing infrastructure  GSM (Intel, AT&T), WiFi (RADAR, Ekahau, Place Lab), FM (MSR)

36. Outline  Defining location  Methods for determining location  Ex. Triangulation, trilateration, etc.  Location Systems  Challenges and Design Decisions  Considerations

37. 37 Challenges and Design Considerations  Beacon-based solutions  Requires the deployment of many devices (typically at least one per room)  Maintenance  Using existing infrastructure  WiFi and GSM  Not always dense near some residential areas  Little control over infrastructure (especially GSM)

38. 38 Beacon-based localization

39. 39 Wifi localization (ex. Ekahau) http://www.ekahau.com/

40. 40 GSM localization Tower IDs and signals change over time! Coverage?

41. 41 PowerLine Positioning  Indoor localization using standard household power lines http://ubicomplab.cs.washington.edu/wiki/PLP

42. 42 Signal Detection  A tag detects these signals radiating from the electrical wiring at a given location

43. 43 Signal Map 1 st Floor 2 nd Floor

44. 44 Example

45. 45 Passive location tracking  No need to carry a tag or device  Hard to determine the identity of the person  Requires more infrastructure (potentially)

46. 46 Active Floor  Instrument floor with load sensors  Footsteps and gait detection

47. 47 Motion Detectors  Low-cost  Low-resolution

48. 48 Computer Vision  Leverage existing infrastructure  Requires significant communication and computational resources  CCTV

49. 49 Other systems?  Inertial sensing  HVACs  Ambient RF  etc.

50. Outline  Defining location  Methods for determining location  Ex. Triangulation, trilateration, etc.  Location Systems  Challenges and Design Decisions  Considerations

51. Considerations  Location type  Resolution/Accuracy  Infrastructure requirements  Data storage (local or central)  System type (active, passive)  Signaling system 51

52. Questions???

53. References  Special thanks to Alex Varshavsky and Gaetano Borriello for their contribution to this content  http://abstract.cs.washington.edu/~shwetak/?Research http://abstract.cs.washington.edu/~shwetak/?Research

54. Assignment #2  Write Short Notes on Topics mentioned in slide 49