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VITP and CARS: A Distributed Service Model and Rate Adaptation for VANETs

VITP and CARS: A Distributed Service Model and Rate Adaptation for VANETs. Liviu Iftode Department of Computer Science Rutgers University. From Vehicular Applications to Services, Security and Networking. VANET Applications based on C2C TrafficView (MDM’04, ACM MC2R’04)

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VITP and CARS: A Distributed Service Model and Rate Adaptation for VANETs

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  1. VITP and CARS: A Distributed Service Model and Rate Adaptation for VANETs Liviu Iftode Department of Computer Science Rutgers University

  2. From Vehicular Applications to Services, Security and Networking • VANET Applications based on C2C • TrafficView (MDM’04, ACM MC2R’04) • EZCab (PerCom’06) • Adaptive Traffic Lights (VTC’07) • Highways with Reservation Lanes (ITCS’07) • Content Sharing for In-Car Entertainment • Vehicular Services • Vehicular Information Transfer Protocol (VITP) (Vanet’05, IEEE JSAC’07)) • Context-aware Migratory Services (IEEE TMC’07) • Security Issues in VANET • Probabilistic Validation of Data Aggregation (Vanet’06) • Trusted Application-Centric Ad-Hoc Networks (MASS’07) • Traffic-Driven Cross-Layer Optimization in VANET • Context-aware Transmission Rate Selection (CARS) • For more information: http://discolab.rutgers.edu Vehicular Applications Services Security Networking

  3. The TrafficView Application • Improve driving safety • Provides driver with a real-time view of the traffic ahead • Prototype demonstrated in real traffic conditions • http://discolab.rutgers.edu/traffic/tvdemo.html

  4. Gas Station Coffee place PTT Server GSM Link 1. Location-Aware Vehicular Services • Many VANET applications follow a client-server model • Centralized vehicular services • Expensive to support • Limited time and space granularity • Distributed services over VANET • Based on C2C communication • Any car can be a client or an ad-hoc server for a request • Stateless or Stateful • Require a trusted service architecture

  5. Vehicular Information Transfer Protocol (VITP) • Application-layer protocol similar to HTTP • VITP Peers • VITP-enabled vehicles • VITP clients and VITP Servers • VITP Messages • Carry location-oriented requests and replies between VITP peers • Updated by VITP Servers to store state of VITP transaction • Examplesof VITP URI VITP Message Format METHOD<uri> VITP/<version_num> Target: [rd_id_dest,seg_id_dest] From: [rd_id_src,seg_id_src] with <speed> Time:<current_time> Expires:<expiration_time> Cache-Control:<directive> TTL:<time_to_live> msgID:<unique_key> Content-Length: <number_of_bytes> CRLF <message body> GET /vehicle/traffic?[cnt=10&tout=2000ms]&tframe=3min GET /service/gas?[cnt=4&tout=1800ms]&price<2USD POST /vehicle/alert?[cnt=*&tout=*]&type=slippery-road

  6. Virtual Ad-Hoc Servers (VAHS) Q • Dynamic collection of VITP peers in the target location of Q that collaborate to resolve Q until its Return Condition is satisfied Gas Station Coffee place

  7. VITP Transactions Dispatch-query phase VAHS-computation phase Dispatch-Reply phase Reply-delivery phase Q VAHS Q Q2 R Q1 Q3 R Q4 R Intermediary nodes Q5 Q7 Q6 VITP Peer VANET node

  8. Accuracy vs. Return Condition • Evaluation of VITP in the IEEE JSAC paper (joint work with University of Cyprus, to appear in 2007)

  9. 2. Transmission Rate Adaptation for Vehicular Ad-Hoc Networks • Content-sharing applications require good throughput • Higher bitrates + high quality links = transmit more data • Higher bitrates + low quality links = higher loss probability • Transmission Rate Adaptation • Which bit rate provides the maximum throughput? • When to switch to another bit rate? • Existing solutions in wireless networks are reactive • Use physical and link layer metrics as estimates of channel quality • Incur time delay due to sampling interval: slow for VANET • Do not account for various dynamics in VANETs caused by fading and mobility • Idea: Use VANET application context information to select the best transmission rate

  10. Context-Aware Rate Selection (CARS) for Vehicular Ad-Hoc Networks • Model the effect of context information on bit error rate starting from real experiments • Use current context information (speed, distance between cars, density) to proactively select the best transmission rate

  11. CARS vs. SampleRate: Detailed Comparison

  12. Throughput: CARS vs SampleRate

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