Caraoke

Omid AbariDeepak Vasisht, Dina Katabi, Anantha Chandrakasan

An E-Toll Transponder Network for Smart Cities1Electronic Toll Transponders80% of the cars in US have themSome states are making it mandatory

2Opportunities

1234576Localization3Opportunities

Adjust traffic-light timingSmart street-parkingDetect red-light runnerOne infrastructure for many smart services

4Challenge: No MAC to Prevent Collision

Physical Isolation

Interference Wireless queryOne car respondsWireless queryAll cars respond at the same timeWhat can we do?5

I don't care 'Cause I've never been so high Follow me to the dark Let me take you past our satellites 6CaraokeA system that delivers smart services using existing e-toll transponders despite interference

Software-Hardware solution: Count carsLocalize carsDecode transponders

Built and evaluated on our campus streets with existing e-toll transponders7Count cars: How to count despite interference? Localize cars

Decode transponders

8Counting Despite InterferenceTime-DomainFreq-Domain

CarrierDataSpike

9Counting Despite InterferenceTime-DomainFreq-Domain

CarrierDataSpike

Caraoke can count transponders despite interference Toll transponders have difference in their carrier frequency10Count cars

Localize cars: How to localize despite interference?

Decode transponders

11Localizing TranspondersLocalization requires knowing the channelHow to extract channels in the presence of interference?

12

Localizing TransponderTime-DomainFreq-Domain

SpikeUse the channel to find the Angle-of-Arrival13Localizing Transponder

14Localizing TransponderCars are always on the road planeIntersect spatial angle with road planeHyperbola

Intersects hyperbolas across multiple readers to find the exact location of the car15Count cars

Localize cars

Decode transponders: How to decode despite interference?

16Solution: Coherent CombiningRealImag17Solution: Coherent Combining

RealImag18Solution: Coherent Combining

RealImag++=Caraoke uses channel information to combine responses coherently and decode the ID19Custom Hardware DesignSelf-SustainingHarvest Solar Energy

20Custom Hardware DesignSelf-SustainingHarvest Solar EnergyLow-CostReplace TX chain with simple PLLPower: 9mW; Cost: $40

21Experimental Results22EvaluationMIT campus- four streetsCaraoke readers were placed on 12.5-feet polesStandard E-ZPass transponders on the cars

23Accuracy of Counting TranspondersHigher accuracy and significantly lower cost than camera-based systems [R.L., JEI13; J.M. Urbana08 ]24Accuracy of Localizing TranspondersCaraoke enables enough accuracy to detect occupied versus available parking spots25Speed Detection AccuracyCaraoke detects the speed to within 8%26Required Time for DecodingCaraoke enables real-time smart city services27Related WorkWireless InterferenceThey require changing transmitter or leverage intrinsic asynchrony in protocols (S. G. Sigcomm12, J. W. Sigcomm08, etc.)Automated PaymentThey require a gate and physical isolation (McDonalds drive-through)Smart ParkingThey require sensors on parking spots or Wi-Fi devices in cars (Street Line, S. M. MobiSys10, S. N. Mobicom13, etc.)28ConclusionA 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 PCB29Omid AbariDeepak Vasisht, Dina Katabi, Anantha Chandrakasan

An E-Toll Transponder Network for Smart Cities30