Vehicular communications: emergency video streams and network coding

Vehicular communications are becoming a reality driven by various applications. Among those applications safe navigation support is of most significance. In designing such navigation safety applications, reliable dissemination of data, i.e., every affected vehicle receives data, is the key issue. Past research focused on the reliable dissemination problem of plain media type (e.g., text) safety messages, whereas we look at the problem of reliable and efficient dissemination of multimedia type (e.g., video, audio) safety information. Considering the potential volume of multimedia traffic in a large metropolis and the unpredictability of vehicular networks (e.g., high speed, partitions, obstacles, radio propagation anomalies, radio interference, etc.), reliable and efficient multimedia dissemination is non-trivial. By using a recently developed technique, network coding, we describe a method for reliable dissemination of video streams in case of emergencies. Simulation results show that in a typical setting, with representative channel errors/losses, our approach yields near 100% delivery ratio as compared to 92% delivery ratio by traditional multicasting. More importantly, the overhead is reduced by as much as 60%. Another important benefit is robustness to temporary disconnections. If the column of vehicles on the road has gaps, network coding jointly with “data muling” using vehicles in the opposite directions can deliver the multimedia files even to intermittently connected components.