Evaluation of Channel Congestion in Dedicated Short-Range Communication Networks

Dedicated Short-Range Communication (DSRC) is the emerging technology that will play a key role in supporting cooperative road safety systems and intelligent transportation systems. This technology is improving rapidly towards the development of prototypes and research platforms used for field experiments. There are many open questions about the DSRC for safety applications. How does this technology meet the stringent requirements of road safety applications? How is the scalability issue in the actual deployment of the technology addressed? With the current spectrum allocations for DSRC and the data traffic generated by cooperative applications, the radio channels could easily be saturated in the absence of effective channel congestion control algorithms. This could result in unstable inter-vehicle communications and eventual failure of the safety system. This research aims to derive a list of design principles for a comprehensive DSRC channel congestion control technique. We survey and classify different methods and establish an appropriate metric for channel condition evaluation. We also find the effective transmission parameters to be adapted in the implementation of channel control techniques. Simulation studies have been conducted to investigate the impact of traffic scenarios on the DSRC network channel state. We evaluate the DSRC network performance under different channel conditions and analyze the adjustment of control parameters by simulation studies. We then propose a prioritized dissemination rate and range controller using a cross-layer design approach to address the channel congestion problem of vehicular DSRC. The controller would receive information and/or feedback from cross-layer sources such as the channel busy ratio from the physical and the medium access control layers and the state data of surrounding vehicles available at the application layer, under the stringent requirements of safety applications. Then it would control the load on the radio channels by firstly adapting the transmission power and secondly adjusting the message exchange rate. This controller will minimize congestion on the safety channels of the DSRC while maximizing the awareness of the host vehicle for detecting and communicating with neighboring vehicles.