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I Am the Antenna: Accurate Outdoor AP Location using smartphones

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I Am the Antenna: Accurate Outdoor AP Location using smartphones. Zengbin. Zhang, Xia Zhou, Weile. Zhang, Yuanyang. Zhang . Gang Wang, Ben Y. Zhao, Haitao – PowerPoint PPT presentation

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Title: I Am the Antenna: Accurate Outdoor AP Location using smartphones


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?
  • NoEffect is not strong
  • Observation

7
Rotation based measurement
  • The difference is significant, because
  • Users 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 WiFis 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 Aps?
  • 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
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