SpinLoc: Spin Around Once to Know Your Location. Souvik Sen Romit Roy Choudhury, Srihari Nelakuditi

Transcription

1 SpinLoc: Spin Around Once to Know Your Location Souvik Sen Romit Roy Choudhury, Srihari Nelakuditi

2 2 Context Advances in localization technology = Location-based applications (LBAs) (iphone AppStore: 6000 apps, Android: 1000 apps)

3 2 Context Advances in localization technology = Location-based applications (LBAs) (iphone AppStore: 6000 apps, Android: 1000 apps) Mostly outdoor apps

4 3 Indoor Localization Technology n Limited by accuracy, wardriving and deployment cost

5 3 Indoor Localization Technology n Limited by accuracy, wardriving and deployment cost GPS ineffective indoors

6 3 Indoor Localization Technology n Limited by accuracy, wardriving and deployment cost GPS ineffective indoors WiFi based: Horus, Place Lab, Horus Most need war-driving

7 3 Indoor Localization Technology n Limited by accuracy, wardriving and deployment cost GPS ineffective indoors WiFi based: Horus, Place Lab, Horus Most need war-driving Infrastructure based: Cricket, Pinpoint High deployment cost

8 3 Indoor Localization Technology n Limited by accuracy, wardriving and deployment cost GPS ineffective indoors WiFi based: Horus, Place Lab, Horus Most need war-driving Infrastructure based: Cricket, Pinpoint High deployment cost WiFi is ubiquitous

9 3 Indoor Localization Technology n Limited by accuracy, wardriving and deployment cost GPS ineffective indoors WiFi based: Horus, Place Lab, Horus Most need war-driving Infrastructure based: Cricket, Pinpoint High deployment cost WiFi is ubiquitous Can we improve WiFi localization without wardriving?

10 Angle of Arrival (AoA) based Localization AP1 AP2 R1 4

11 Angle of Arrival (AoA) based Localization AP1 AP2 R1 4

12 Angle of Arrival (AoA) based Localization AP1 AP2 R1 4

13 Angle of Arrival (AoA) based Localization AP1 AP2 R1 4

14 Angle of Arrival (AoA) based Localization AP1 AP2 AP with multiple antennas. Enterprise Settings. R1 4

15 Angle of Arrival (AoA) based Localization AP1 AP2 AP with Multiple antennas Enterprise Settings R1 5

16 Angle of Arrival (AoA) based Localization AP1 AP2 AoAwith localization phone. AP Multiple on antennas Enterprise Settings R1 5

17 Angle of Arrival (AoA) based Localization AP1 AP2 AoAwith localization phone. AP Multiple on antennas Enterprise Settings R1 5

18 Angle of Arrival (AoA) based Localization AP1 AP2 AoAwith localization phone. AP Multiple on antennas Enterprise Settings Privacy preserving. R1 5

19 We propose SpinLoc AoA based localization aided by user spins 6

20 Indoor Multipath 7

21 Indoor Multipath Direct Path Reflected Path 7

22 Direct Path Energy Direct Path 8

23 Direct Path Energy Direct Path 8

24 Direct Path Energy Direct Path Energy Direct Path 8

25 Direct Path Energy Direct Path Energy Direct Path 9

26 Direct Path Energy Direct Path Energy Direct Path 9

27 Direct Path Energy - Human body predominantly water - 2.4Ghz is water s resonant frequency Direct Path Energy Direct Path 9

28 Direct Path Energy - Human body predominantly water - 2.4Ghz is water s resonant frequency Direct Path Energy Direct Path Hypothesis: Direct path energy minimum when human perfectly blocks phone 9

29 9 Direct Path Energy Direct Path Human

30 Direct Path Energy Direct Path Human 10

31 Direct Path Energy Direct Path Energy Compass Orientation Direct Path Human 10

32 Direct Path Energy Direct Path Energy Compass Orientation Direct Path Human 10

33 Direct Path Energy Direct Path Energy Compass Orientation Direct Path Human 11

34 Direct Path Energy Direct Path Energy Compass Orientation Direct Path Human 11

35 Direct Path Energy Direct Path Energy Minimum when user blocks phone Compass Orientation Direct Path Human 11

36 Direct Path Energy 1.4 Normalized Direct Path Energy Direct Path Energy Normalized Direct Path Energy Angle Compass Orientation Angle Direct Path Human 12

37 Direct Path Energy 1.4 Normalized Direct Path Energy Direct Path Energy Normalized Direct Path Energy Angle Compass Orientation Angle Direct Path Human 13

38 Direct Path Energy Normalized Direct Path Energy AoA = ( Compass orientation corresponding to minimum direct path energy Angle ) mod 360 Direct Path Human 13

39 RSSI as Direct Path Energy? Direct Path Reflected Path 14

40 RSSI as Direct Path Energy? Direct Path Reflected Path RSSI 14

41 Facing

42 Facing RSSI = Direct + Reflected

43 Facing RSSI = Direct + Reflected 20 db + 5 db

44 Facing RSSI = Direct + Reflected 20 db + 5 db = 25 db

45 Facing RSSI = Direct + Reflected 20 db + 5 db = 25 db Blocking Direct + Reflected

46 Facing RSSI = Direct + Reflected 20 db + 5 db = 25 db Blocking Direct + Reflected 10 db + 15 db = 25 db

47 But how do we estimate direct path energy? Using off-the-shelf WiFi cards? 17

48 Phase Phase of H(f) Amplitude Amplitude of H(f) Channel Frequency Response Subcarrier f Subcarrier Channel Frequency Response 18

49 Channel Frequency Response Phase Amplitude Amplitude of H(f) Phase of H(f) Subcarrier f Subcarrier 18

50 Channel Frequency Response Phase Amplitude Amplitude of H(f) Phase of H(f) Subcarrier f Subcarrier IFFT Power delay profile SNR in db Delay in microseconds 19

51 Channel Frequency Response Direct path Energy Phase Amplitude Amplitude of H(f) Phase of H(f) Subcarrier f Subcarrier IFFT SNR in db Power delay profile Reflected paths Delay in microseconds 19

52 Localization using AoA 20

53 Localization using AoA Actual Direction Estimated Direction 20

54 Localization using AoA Actual Direction Estimated Direction 20

55 Localization using AoA Actual Direction Estimated Direction 21

56 Localization using AoA Actual Direction Estimated Direction 21

57 Localization using AoA Actual Direction Estimated Direction Centroid 21

58 Localization using AoA and RSSI Actual Direction Estimated Direction 22

59 Localization using AoA and RSSI Actual Direction Estimated Direction 22

60 Localization using AoA and RSSI Actual Direction Estimated Direction 22

61 Localization using AoA and RSSI Actual Direction Estimated Direction 22

62 Localization using AoA and RSSI Actual Direction Estimated Direction Centroid 22

63 Localization using AoA and RSSI Actual Direction Estimated Direction Centroid 1. Angle estimation error: Difference between actual and estimated direction 22

64 Localization using AoA and RSSI Actual Direction Estimated Direction Centroid 2. Localization error: 1. Angle estimation error: Difference between actual Difference between actual and estimated location and estimated direction 22

65 Performance Evaluation n Used off-the-shelf Intel 5300 cards to obtain direct path energy n Evaluated SpinLoc at various settings: Engineering Building 30 locations 3-5 APs Cafeteria 25 locations 3-4 APs n Compare with RSSI based trilateration scheme 23

66 Angle Estimation Error 50 Mean angle error SNR in db 24

67 Angle Estimation Error 50 Mean angle error SNR in db Average error = 20 degrees, for APs stronger than 20dB RSSI 24

68 Localization Error CDF Using only angle Using angle + RSSI Using only RSSI Localization error in meter Average localization error = 5 meters 25

69 SpinLoc: Closing Thoughts n AoA based localization without wardriving Human body attenuates direct path to APs SpinLoc identifies this direct path, extract AoA Triangulates to estimate location SpinLoc Limitations: n Requires user involvement: spin once to know your location n Phone listens to WiFi traffic while user spins May not be able to transmit data to the internet while spinning n Depends on existence of direct path from AP May be heavily attenuated n Require extensive testing in crowded environments 26

70 Questions, comments? Duke SyNRG Research Group