1. I AM THE ANTENNA: ACCURATE OUTDOOR AP LOCATION USING SMARTPHONES ZENGBIN ZHANG, XIA ZHOU, WEILE ZHANG, YUANYANG ZHANG GANG WANG, BEN Y. ZHAO, HAITAO ZHENG DEPARTMENT OF COMPUTER SCIENCE, UNIVERSITY OF CALIFORNIA, SANTA BARBARA, USA

2. OUTLINE  Introduction  Accurate AP Location  Directional analysis  User navigation  Implementation  Evaluation  Conclusion

3. INTRODUCTION

4. UBIQUITOUS BROADBAND ACCESS  Cisco: WiFi traffic will surpass wired IP traffic in 2015  Governments and companies are deploying public WiFi networks  High Density  We need well tuned and managed WiFi networks

5. CONVENTIONAL AP LOCATION METHODS

6. INSIGHT: THE BODY BLOCKING EFFECT  Can we use this to detect AP location?  No…Effect is not strong  Observation

7. ROTATION BASED MEASUREMENT  The difference is significant, because  User’s body is much larger than the phone  User is close to the phone  We can emulate a directional antenna just by rotating with Smartphones

8. GENERALITY OF THE EFFECT  Devices  Motorola Droid, HTC G1 (Android)  LG Fathom (WM 6.5)  iPhone4 (iOS)  Protocols  802.11 b/g  802.11n (MIMO)  Different users  7 users in our lab  Environments  Outdoor LOS/Non-LOS  Different distances to AP

9. GENERALITY OF THE EFFECT

10. ACCURATE AP LOCATION

11. USER ROTATION BASED AP LOCATION

12. MODELING THE BODY AS A SIGNAL OBSTACLE

13. OUR DIRECTIONAL ANALYSIS MODEL  Signal degradation occurs at a range of directions

14. DIRECTIONAL ANALYSIS

15. DIRECTIONAL ANALYSIS IS NON-TRIVIAL  Minimum RSS direction?  Using Minimum RSS direction would cause large errors

16. LOCATING THE BLOCKING SECTOR  Find the sector with the largest RSS degradation

17. NAVIGATION  How does a user navigate using directional hints?  Strawman design: periodic Refine AP direction every 20m  However, nothing is perfect Temporal/spatial variation  Adaptive method  Measurement confidence The similarity of measured RSS profile and ideal RSS profile  If confidence is high Walk further between measurements

18. CONFIDENCE OF DIRECTIONAL ANALYSIS  Borealis uses confidence value of each estimate to control how often a user needs to repeat the direction estimate.

19. A BOREALIS PROTOTYPE  Application layer  Leveraging WiFi scan to read RSS Default scan is very slow Scanning all channels each time  OS layer  Modified WiFi driver Only scan the channel the AP is on  Two benefits Accelerate the process: 10 seconds per rotation (10 times faster) Save power: WiFi’s energy consumption is 14 times less

20. EVALUATION

21. TESTING SCENARIOS

22. ACCURACY OF DIRECTIONAL ANALYSIS  Rotation at 400 + locations for each scenario  Absolute angular error = |detected direction – actual direction|  We compared Borealis to  Offline analysis Clustering-based learning algorithm Optimized by a large training set  GUIDE RSS gradient based  Min RSS Minimum RSS direction based

23. ACCURACY OF DIRECTIONAL ANALYSIS  Rotation at 400 + locations for each scenario  Absolute angular error = |detected direction – actual direction|  We compared Borealis to  Offline analysis Clustering-based learning algorithm Optimized by a large training set  GUIDE RSS gradient based  Min RSS Minimum RSS direction based

24. NAVIGATION EFFICIENCY

25. LOCATION INDOOR AP S ?  Most APs are mounted inside buildings  They mounted the AP on a table in a office trailer  Try to locate it outside in Complex LOS/NLOS environment  More complex concrete buildings would be much harder

26. CONCLUSION  AP location requires cheap, online and accurate solutions  Very beneficial in network management  Borealis: an efficient and accurate solution for WiFi AP location  Leveraging the body blocking effect on smartphones  General to a wide rage of devices and systems  Feasible even in complex environments

27. THANK YOU