DySCO: A DYnamic Spectrum and COntention Control Framework for Enhanced Broadcast Communication in Vehicular Networks

Recently, the IEEE 1609.4 protocol has been defined to enable multi-channel operations in a vehicular environment, and to guar- antee interference-free co-existence of safety-related and non-safety related applications in the same network. To meet these goals, the protocol assumes strict time synchronization among vehicles, and time/frequency separation in the Dedicated Short Range Commu- nication (DSRC) band. However, recent studies have demonstrated that this approach might not be suitable for safety-related broadcast applications with strict Quality-of-Service (QoS) requirements. In this paper, we investigate the potentials of Cognitive Radio (CR) technology to enhance the delivery ratio of safety-related broadcast applications in a multi-channel vehicular scenario. In this research field, we propose three novel contributions: (i) we introduce an analytical model to study the delivery ratio of broadcast applica- tions in IEEE 802.11p/1609.4 multi-channel vehicular networks, and the impact of MAC and PHY parameters on the system per- formance; (ii) we propose a framework to jointly decide the opti- mal values of the Contention Window size (CW) at the MAC layer and of the Control CHannel (CCH) bandwidth at PHY layer, so that each vehicle is able to transmit all its safety data during the CCH interval with a minimum MAC collision probability, and (iii) we discuss the framework implementation in a realistic vehicular scenario. Our on-demand bandwidth allocation algorithm utilizes vacant frequencies in the DSRC band to increase the bandwidth of the CCH, leveraging the spectrum agile capabilities offered by the CR technology. Simulation results confirm the effectiveness of our proposal in enhancing the delivery rate of broadcast applications under varying network scenarios and load conditions.