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Abstract
The concept of motor vehicles interacting with their surroundings using wireless communications is seen as a promising new way to improve road safety and traffic congestion on our increasingly overcrowded roads. While most of the framework has been defined and the necessary wireless spectrum allocated, there still remains many important issues that must be resolved before vehicular communication could realize its full potential. Reliability is one of such issues addressed in this thesis. Packets carrying vital safety information can get lost in harsh and extremely dynamic wireless environment, making reliable communication a challenging problem for vehicles. This thesis proposes novel approaches for packet retransmission techniques to recover from lost packets quickly, effectively, and efficiently in vehicular communication environment. Bandwidth efficiency of the proposed loss recovery techniques is achieved by applying the technique of Network Coding, which allows more lost packets to be recovered per retransmission. Using analytical modeling and computer simulation, the performance of the proposed loss recovery techniques are shown to be significantly better than the previously proposed retransmission techniques. Specifically, it has been shown that Network Coding can achieve higher reliability for the same bandwidth overhead, or higher bandwidth efficiency for the same level of reliability. The packet loss correlation between different receivers has a huge impact on the lost packet recovery. This thesis reports original results from extensive practical experiments to demonstrate that packet losses can be highly uncorrelated even between closely located receivers, providing valuable evidence that Network Coding is a practical concept to pursue for vehicular communications. A final contribution of this thesis is the design and analysis of a dynamic resource scheduling technique that, for a target safety communication reliability, allows efficient integration of both safety and non-safety communication applications over the same radio.