Reliability Analysis of DSRC Wireless Communication for Vehicle Safety Applications

1. Reliability Analysis of DSRC Wireless Communication for Vehicle Safety Applications Fan Bai and Hariharan Krishnan General Motors Corporation Presented by Long Vu CS598JH – Fall 07

2. Vehicle Safety Communication through Dedicated Short Range Communication (DSRC) How Reliable is the Dedicated Short Range Communication?

3. Reliability of Dedicated Short Range Communication No information about traffic/obstacle on the real freeway • Two Experimental Setups • Real Freeway (many obstacles) • Test (in General Motors – no obstacle) • Performed 3 times • Car Equipments • 802.11p-based DSRC radio • Directional antenna • GPS devices • Application to exchange and display messages • Experiment Execution • Cars periodically broadcast each 0.1 (s) (location, velocity, braking status, …) • Cars within 300m can capture • Record a log file

4. Next… Recall: How Reliable is Dedicated Short Range Communication? • Reliability of DSRC in Link Layer • Packet Delivery Ratio • Distribution of Consecutive Packet Drops • Reliability of DSRC in Application Layer • Tolerance Time Window • Reliability of DSRC in Application Layer • Relationship between Link Layer Reliability Application Layer Reliability

5. Reliability of DRSC in Link Layer (1) • Packet Delivery Ratio • #successful received packets/ #total transmitted packets Freeway Test • Test environment has better performance • Freeway is a harsh environment for DSRC

6. Reliability of DRSC in Link Layer (2) • Distribution of Consecutive Packet Drops P(1 packet dropped) = 4/6 P(2 packets dropped) = 2/6 Freeway Test • DSRC doesn’t have burst most of the time • Packet drop has the memory less property

7. Next… Recall: How Reliable is Dedicated Short Range Communication? • Reliability of DSRC in Link Layer • Packet Delivery Ratio • Distribution of Consecutive Packet Drops • Reliability of DSRC in Application Layer • Tolerance Time Window • Reliability of DSRC in Application Layer • Relationship between Link Layer Reliability Application Layer Reliability

8. Tolerance Time Window T • In application perspective, packet loss is acceptable • Within a period of time T, at least one packet should be received successfully  application is reliable • T in the range of [0.3 sec, 1.0 sec] • Application Reliability: Probability of receiving at least one packet from sender during T

9. Reliability of DSRC in Application Layer • Experiment • At each time t0, app checks whether a packet is received during [t0-T, t0] • Record locations of sender and receiver Freeway Test

10. Relationship between Link Layer and Application Layer Reliability • T: Tolerance Time Window • t: broadcast interval (t = 0.1s) • M: # packets broadcasted during T (M=T/t) d • Pcomm(d): prob. of successfully receiving each packet at distance d in Link layer • Papp(d): prob. of successfully receiving at least one packet at distance d in Application layer, during a Tolerance Time Window T

11. Relationship between Link Layer and Application Layer Reliability • Assumption: packet drops are independent • Pcomm(d): prob. of successfully receiving each packet at distance d in Link layer • Papp(d): prob. of successfully receiving at least one packet at distance d in Application layer, during a Tolerance Time Window T • Papp(d)= 1 – Pr(receiving no packets from M consecutively sent packets during T) Papp(d)= 1 – [1-Pcomm(d)]M = 1 – [1-Pcomm(d)]T/t

12. Lessons to Take Home • Pros • The first reliability measurement of DSRC for Vehicle Safety Communication Applications • Real experiments with highways • Analysis model of reliability of DSRC between Link Layer and Application Layer • Independent packet drop • Cons • The analysis can’t be applied for Commerce and Convenience Applications • No highway traffic information