Indoor-Positioning Using RSSI: DOD-Based Technique Versus RSSI-Ranging Technique

Transcription

1 1 IWATE UNIVERSITY JAPAN Indoor-Positioning Using RSSI: DOD-Based Technique Versus RSSI-Ranging Technique Naoki Honma, Ryota Tazawa, Kota Kikuchi, Atsusi Miura, Yusuke Sugawara, Hiroto Minamizawa Graduate School of Engineering, Iwate University Embedded Resource Integration, Inc.

2 Contents 2 Background Indoor positioning techniques relying on RSSI Simulation: comparison study RSSI-ranging versus DOD-triangulation Experiment: performance evaluation Positioning accuracy of DOD-triangulation Hybrid technique: DOD + PDR Conclusion

3 Background 3 Why Indoor Positioning? GNSS Satellite signal is not available in an indoor environment Indoor positioning system using beacons COTS (Commercial-Off-The-Shelf ) devices Accurate? Beacon Beacon Accurate positioning is a key challenge now

4 Well-known Positioning Techniques RSSI:high =near RSSI*-ranging Target RSSI:low =far Poor accuracy for distant target due to multipath Tx1 Tx2 Fingerprinting Measure RSSI Tx3 Database of RSSI Data matching In need of prior-measurement of RSSI distribution Database susceptible to environmental change Another approach? *RSSI:Received Signal Strength Indicator 4

5 BLEGONIO: DOD-Based Positioning Each beacon transmits four BLE a) signals using four different directivities. a) BLE: Bluetooth Low Energy b) DOD: Direction of Departure DOD b) 1 #4 #3 #16 #15 #14 DOD4 Bluetooth signal #1 #2 Bluetooth signal #5 #9 DOD2 #6 #7 #8 #10 #11 #12 DOD3 Bluetooth signal #13 The handset calculates DOD information from RSSIs, and estimates its location by triangulation.

6 Developed Beacon Overview 6 Array antenna Switching circuit Feed network Beacon

7 Microsoft IPSN IPSN 2017 The 16 th ACM/IEEE International Conference on Information Processing in Sensor Networks April 18-21, 2017 Pittsburgh, Pennsylvania, USA Two-floor site Beacons DOD-beacon 38.5m 26m iphone5c

8 Error in Meters Microsoft IPSN Results (2D-category) PDR PDR Our Beacons We got the best record in the radio-wave category

9 Contents 9 Background Indoor positioning techniques relying on RSSI Simulation: comparison study RSSI-ranging versus DOD-triangulation Experiment: performance evaluation Positioning accuracy of DOD-triangulation Hybrid technique: DOD + PDR Conclusion

10 Question: which is better? RSSI-Ranging DOD Triangulation d 1 d i Terminal node θ 1 Terminal node θ i Tx-1 Beacon 1 Tx-i Beacon #i Multipath-fadings Tx-1 Tx-i Beacon 1 Beacon #i DOD-accuracy? No one has compared them using fair conditions. 10

11 Simulation model 11 Rician-fading model k-factor = h LOS F 2 h NLOS F 2 Δφ θ h LOS h NLOS Generating channel h LOS: Direct-path channel h NLOS : Indirect-path channel Channel matrix:h = h LOS + h NLOS Geometric-optics approach Zero-mean gaussian random matrix

12 Simulation model Environment Beacon 2 (0, 25) 37 m 12 Beacon 3 (37, 25) 25 m y (0,0) Beacon 1 p u = (x u, y u ) Terminal node O(0,0) x 3-element array (37, 0) Beacon 4

13 Average distance error [m] Results 13 RSSI-ranging versus DOD-triangulation DOD RSSI Ranging 5.6m 1.1m k-factor [db] DOD-triangulation yields 5-times better accuracy

14 Contents 14 Background Indoor positioning techniques relying on RSSI Simulation: comparison study RSSI-ranging versus DOD-triangulation Experiment: performance evaluation Positioning accuracy of DOD-triangulation Hybrid technique: DOD + PDR Conclusion

15 Experiment 15 Environment Tx Tx m Obstacle 5 m m 31 5 m m m m m 5 m 5 m m Obstacle Tx3 25 m 3 m Tx5 Tx4 y 15 x

16 Experiment 16 Photos Beacon Obstacle Beacon Smart phone (iphone5c)

17 Experiment 17 Example result Estimated DOD P27 Beacons Beacon True Estimated DODs can be well estimated at the mobile terminal

18 CDF [%] Experiment *CDF: Cumulative Distribution Function Overhead 1.05m Browsing * m Distance error [m] High accuracy is attained

19 Contents 19 Background Indoor positioning techniques relying on RSSI Simulation: comparison study RSSI-ranging versus DOD-triangulation Experiment: performance evaluation Positioning accuracy of DOD-triangulation Hybrid technique: DOD + PDR Conclusion

20 Hybrid method: DOD-beacon + PDR * 20 *PDR: Pedestrian dead reckoning PDR: Relative route + Assumed current position: x, y Estimated DOD transition Measured DOD transition Comparison θ 1 0 Tx θ 2 θ n Rx x, y Find position (x, y) with most similar DOD transition 20

21 DOD Hybrid method: DOD-beacon + PDR Tx DOD transition Rx θ DOD 0 Relative route by PDR x, y Time Find position (x, y) with most similar DOD transition 21

22 Measurement setup -20 N Measurement conditions Route Length Meas. period A 3.0m 15 s B 4.0m C 9.2 m 30 s D 12.0 m Handset iphone 5c Num. of beacons 4 Height of ant m Signal Bluetooth (2.4GHz) Faculty / Graduate School of Engineering, Num. Iwate of trials 22 University, 30 Japan times/ route

23 Environment Rx Tx2 Tx3 Tx m Tx1 D C A B 23

24 Acceleration [m/s 2 ] PDR by counting vertical acceleration variance Example: acceleration raw data 2 Acceleration Detected step Time [s] Footsteps are easily detected using COTS * device *COTS : Commercially-off-the-shelf 24

25 Route estimation by PDR only Tx2 Tx3 [m] 1 0 Actual Estimation -1-2 Route D -3 Tx1 Tx Well estimate relative route [m] 25

26 DOD [deg] Estimating DOD transition Tx2 3 2 Tx Correct (x, y) Observed PDR 1 PDR 2 PDR 3 0 Route D Tx1 Tx4 Observed at Tx Time [s] Examples of DOD transition Correct route yields DOD transition similar to observed one 26

27 Estimation example 1 Tx Actual pos. Estimated pos. Actual route Estimated route [deg] Position is successfully estimated by proposed method 27

28 Accuracy comparison 1 Method A B C D Average Hybrid method 0.32 m 0.28 m 0.50 m 0.51 m 0.40 m DOD only 0.41 m 0.88 m 0.58 m 1.99 m 0.97 m Average 0.97 m (DOD only) 0.40 m (hybrid): two-fold improvement 28

29 Contents 29 Background Indoor positioning techniques relying on RSSI Simulation: comparison study RSSI-ranging versus DOD-triangulation Experiment: performance evaluation Positioning accuracy of DOD-triangulation Hybrid technique: DOD + PDR Conclusion

30 Conclusion 30 Indoor-Positioning Using RSSI RSSI-ranging technique vs. DOD-based technique Two RSSI-based methods are compared RSSI-ranging: RSSI is directly translated to distance DOD-triangulation: RSSI difference is translated to DODs Simulation DOD-triangulation yields five-fold higher k = 10 db Experiment in indoor environment DOD only: Accuracy: 1.05 ~1.21 DOD+PDR: Accuracy: 0.4

31 31 Thank you! Contact: Naoki Honma, Iwate Univ.: Atsushi Miura, ERi, Inc.: honma[at]iwate-u.ac.jp miura[at]erii.co.jp