Reliable Network Coded MAC in Vehicular Ad-Hoc Networks

We consider the problem of designing cooperative driver assistance and collision warning systems in vehicular networks. In this problem each car has a small size state information message that should be received by its neighborhood within a short lifetime of L timeslots. Because of the safety nature of the application, communication reliability (success probability) and delay are of critical importance. In a repetition-based MAC scheme, each car retransmits its safety message w times in a time frame of L timeslots. Based on the proposed opportunistic network coding in this paper, given the local feedback information and already heard messages, each node tries to find the best message combining strategy such that the number of nodes that can instantly decode an uncoded packet is maximized. Simulation results show that the proposed scheme outperforms the random linear network coding as well as the uncoded case in terms of message loss probability. Also it results in lower average message reception delay compared to random linear network coding.