Xiaofan Jiang, Chieh -Jan Mike Liang, Kaifei Chen, Ben Zhang, Jeff Hsu

1. Design and Evaluation of a Wireless Magnetic-basedProximity Detection Platform for Indoor Applications Xiaofan Jiang, Chieh-Jan Mike Liang, Kaifei Chen, Ben Zhang, Jeff Hsu Jie Liu, Bin Cao, and Feng Zhao Microsoft Research Asia 20120730-Neight

2. Outline • MOTIVATION • PROXIMITY ZONE • Empirical Definition • EVALUATION OF EXISTING TECHNOLOGIES • LIVESYNERGY PLATFORM • EVALUATION OF LIVESYNERGY • APPLICATION DEPLOYMENT • CONCLUSIONS

3. Motivation • To make applications intuitive to human users, the discovered objects in the environment must be within the personal interaction sphere • Computer automatically wake up • Refrigerator change its user interface • Many typical low power communication technologies, (Bluetooth, ZigBee) have difficulties maintaining robust communication zones

4. Contributions • propose methodologies and systematically compare the proximity zones created by various wireless technologies(BLE, ZigBee, and RFID reader) • Design, Implement, and Evaluate a magnetic-induction based wireless proximity sensing platform • Deploying LiveSynergy in an real-world application

5. PROXIMITY ZONE • Boundary sharpness: boundary of proximity zone should be binary • Boundary consistency: detection should be consistent over time

6. PROXIMITY ZONE • Obstacle penetration: Beaconing node andlistening node can be mobile and against obstructions • Additional metrics: 1. Range and geometric shape of zones 2. Beaconing frequency achievable 3. Power consumption 4. Form-Factor of the mobile tag 5. Cost of overall system

7. Classification of Points • Broadcasts at fixed frequency f (packets ) • P =a point in space at a distance of (, , ) from the beacon

8. Classification of Zones • white/grey boundary: {P | Color(P, t, t’) = white} {P | Color(P, t, t’) = grey} if x,if x’ represents the decision boundary • grey/black boundary: if x,if x’

9. Three proximity zones

10. Proximity Zones Questions?

11. Classifier • Use support vector machines (SVM) as the classifier seeks maximum-margin hyperplane to separate two classes • w and b are the parameters to define the hyperplane to separate the two classes.

12. Classifier • Two user-definable parameters: • Error tolerance: - Smooth boundaryvs. non-smooth boundary • Tradeoff between training loss and regularization • Cost parameter C • Strictness: -Expect the white zone and the black zone contain no grey points -Related to error tolerance but non-symmetry

13. Classifier • Cost parameter C: the cost of false positive C’: the cost of false negative C’ • Strictness parameter:

14. Kernel Trick • RBF kernel as the kernel function • Classifier: • RBF kernel

15. Matrix • Size: Size of the white and grey zone, which can be computed numerically based on the boundaries. • Boundary sharpness: • Fitness: How well the zone boundaries fit the data, or a confidence measure of the proximity zone classification.

16. Classifier Questions?

17. Boundary Sharpness and Consistency • Hardware setup: • TI CC2540 BLE dev boards (transmitting on 2.4 GHz at 0 dBm), • A pair of TelosB motes with 802.15.4-compliant TI CC24240 radio(transmitting on 2.4 GHz at 0 dBm) • A Impinj Speedway R1000 RFID reader (transmitting on 902 MHz at 8 dBm)

18. Boundary Sharpness and Consistency • Parameters: • packet reception data is collected over a period of 200 seconds • WPRR using a windows size of 3 seconds and • Strictness parameter = 0.99 • Results:

19. Boundary Sharpness and Consistency

20. Human Obstacle Penetration • The user carries the receiver in the right pants pocket - calculate PRR from 500 packets as the user changes the body orientation by 90 each round at each distance

21. Additional Metrics • Signal propagation and geometry: RFID antennas usually have a radiation angle less than 180 degrees • Form Factor and Costs: RFID can produce a more consistent and smaller grey zone 802.15.4 and BLE have advantages in both form factor and costs.

22. Evaluation Questions?

23. LIVESYNERGY PLATFORM • Pulse Transmitter:(use AC power) Four primary hardware • microcontroller (MCU) and radio • magnetic transmitter tuned at 125kHz • Energy metering • mechanical relay foractuation.

24. LIVESYNERGY PLATFORM • Link Receiver: ( battery-powered) Three primary hardware 9.2cm ×5.8cm × 2.3cm enclosure • MCU and radio • 3D magnetic coil • wake up chip

25. Boundary Sharpness and Consistency

26. Body orientation vs. distance • human body has very little impact on the MI signal propagation

27. Additional Metrics • Geometry: two dimensions extends to all directions, covering 360◦ • Range: maximum range (i.e., radius) is around 5m

28. APPLICATION DEPLOYMENT Diners enter the cafeteria from the entrance at the lower left corner at different times

29. Experment • Each diner takes a different route and visits various food counters on the way • Recorded a video as the customers walk around the cafeteria purchasing food. - Use video timestamps

30. Result

31. Summary • Values: • Propose methodologies and systematically compare the proximity zones • Deploying LiveSynergy in an real-world application • Future? • MI still can implement in mobile phone…