1. Omid Abari Deepak Vasisht, Dina Katabi, Anantha Chandrakasan An E-Toll Transponder Network for Smart Cities

2. Electronic Toll Transponders 80% of the cars in US have them Some states are making it mandatory

3. Opportunities 1 2 3 4 5 7 6 Localization

4. Opportunities Adjust traffic-light timing Smart street-parking Detect red-light runner One infrastructure for many smart services

5. Challenge: No MAC to Prevent Collision Physical Isolation Interference Wireless query One car responds Wireless query All cars respond at the same time What can we do?

6. I don't care 'Cause I've never been so high Follow me to the dark Let me take you past our satellites

7. Caraoke A system that delivers smart services using existing e-toll transponders despite interference Software-Hardware solution: – Count cars – Localize cars – Decode transponders Built and evaluated on our campus streets with existing e-toll transponders

8. Count cars: How to count despite interference? Localize cars Decode transponders

9. Counting Despite Interference Time-Domain Freq-Domain Carrier Data Spike

10. Counting Despite Interference Time-Domain Freq-Domain Carrier Data Spike Caraoke can count transponders despite interference Toll transponders have difference in their carrier frequency

11. Count cars Localize cars: How to localize despite interference? Decode transponders

12. Localizing Transponders Localization requires knowing the channel How to extract channels in the presence of interference?

13. Localizing Transponder Time-Domain Freq-Domain Spike Use the channel to find the Angle-of-Arrival

14. Localizing Transponder

15. Cars are always on the road plane Intersect spatial angle with road plane Hyperbola Intersects hyperbolas across multiple readers to find the exact location of the car

16. Count cars Localize cars Decode transponders: How to decode despite interference?

17. Solution: Coherent Combining Real Imag

18. Solution: Coherent Combining Real Imag

19. Solution: Coherent Combining Real Imag ++= Caraoke uses channel information to combine responses coherently and decode the ID

20. Custom Hardware Design Self-Sustaining – Harvest Solar Energy

21. Custom Hardware Design Self-Sustaining – Harvest Solar Energy Low-Cost – Replace TX chain with simple PLL Power: 9mW; Cost: $40

22. Experimental Results

23. Evaluation MIT campus- four streets Caraoke readers were placed on 12.5-feet poles Standard E-ZPass transponders on the cars

24. Accuracy of Counting Transponders Higher accuracy and significantly lower cost than camera-based systems [R.L., JEI’13; J.M. Urbana‘08 ]

25. Accuracy of Localizing Transponders Caraoke enables enough accuracy to detect occupied versus available parking spots

26. Speed Detection Accuracy Caraoke detects the speed to within 8%

27. Required Time for Decoding Caraoke enables real-time smart city services

28. Related Work Wireless Interference – They require changing transmitter or leverage intrinsic asynchrony in protocols (S. G. Sigcomm’12, J. W. Sigcomm’08, etc.) Automated Payment – They require a gate and physical isolation (McDonald’s drive-through) Smart Parking – They require sensors on parking spots or Wi-Fi devices in cars (Street Line, S. M. MobiSys’10, S. N. Mobicom’13, etc.)

29. Conclusion A system for delivering smart services using existing e-toll transponders Can count, localize and decode transponders in the presence of interference We built it into a small PCB

30. Omid Abari Deepak Vasisht, Dina Katabi, Anantha Chandrakasan An E-Toll Transponder Network for Smart Cities