1. Sybot: An Adaptive and Mobile Spectrum Survey System for WiFi Networks Kyu-Han Kim, Alexander W. Min,Kang G. Shin Mobicom 2010 -Twohsien 2010.12.08

2. OUTLINES  Motivations  Architecture  System Prototype  Evaluation  Conclusion

3. OUTLINES  Motivations  Architecture  System Prototype  Evaluation  Conclusion

4. Motivations  Limitations of Existing Approaches Accuracy and repeatability Efficiency and flexibility Adaptation and awareness

5. OUTLINES  Motivations  Architecture  System Prototype  Evaluation  Conclusion

6. Architecture  Overview of Sybot Periodic and aperiodic monitoring Decomposition Use of spatio-temporal variance Adaptive and controllable monitoring  Adaptive Spectrum Monitoring

7. Architecture

11.  Overview of Sybot  Adaptive Spectrum Monitoring Complete Monitoring Selective Monitoring Diagnostic Monitoring

12. Architecture – Complete monitoring  Building a comprehensive map  Grid size  Temporal variance

13. Architecture – Selective monitoring  Reference grids  Smallest set  Accuracy

14. Architecture – Diagnostic monitoring  Detecting abnormal changes  Speculating measurement areas  Exploiting external network monitoring information

15. OUTLINES  Motivations  Architecture  System Prototype  Evaluation  Conclusion

16. System Prototype of Sybot – Software Implementation  Mobility control module  Spectrum monitoring module

17. System Prototype of Sybot – Hardware Implementation  iRobot  RB230 wireless router  Sonar sensor

18. OUTLINES  Motivations  Architecture  System Prototype  Evaluation  Conclusion

19. Evaluation  Testbed Setup 12 Aps Long-term: three times a day Short-term: 5-10 times a day Unit grid size: 20in * 30in

20. Evaluation  Repeatability  Impact of grid size  Reducing the space to measure  Gains form adaptive selection of reference grids  Diagnosis of abnormal spectrum condition

21. Evaluation - Repeatability

22. Evaluation - Impact of grid size

24. Evaluation – Reducing the space to measure

27. Evaluation – Gains from adaptive selection of reference grids

28. Evaluation – Diagnosis of abnormal spectrum condition

29. OUTLINES  Motivations  Architecture  System Prototype  Evaluation  Conclusion

30. Conclusion  Discussion Multiple Aps Multiple Sybots  Concluding Remarks Three monitoring techniques that significantly reduce the measurement overhead Provide accurate spectrum-monitoring result under dynamic spectrum conditions Determine trade-off between accuracy and efficiency