Abstract
Accurate implementation of communications protocol stacks is unavoidable, however the traditional protocol stack designed for Dedicated Short Range Communications (DSRC) does not efficiently support safety applications. DSRC protocol stack must satisfy some stringent performance requirements by safety applications in challenging scenarios such as heavy road traffic. Several communications solutions, and industry standards including the recently published SAE-J2945.1 standard, are proposed for vehicular safety systems, but by what means such systems can address the stringent requirements of safety applications and the scalability issue in their actual deployment is still an open question. With the current spectrum allocations for vehicular DSRC and the data traffic generated by cooperative applications, the radio channels could be easily saturated in the absence of effective control algorithms, resulting in unstable inter-vehicle communications and eventually failure of the system. The results of several simulation studies are presented in this paper to evaluate the DSRC channel and understand the parameters affecting its state.
This paper proposes a cross-layer designed controller for inter-vehicle safety messaging to address the channel congestion problem of vehicular networks. The proposed controller enjoys a design supporting direct and in-direct interfacing between layers with awareness control aiming at serving the stringent requirements of DSRC safety applications. The message dissemination controller receives feedback such as channel utilization, outdated packets and vehicle density information from cross-layer sources to control the load on the radio channels by adjusting the transmit power and message intervals. The necessity of instant adjustments requires the mechanism to be utilized with a decentralized yet cooperative coordination. The aim of this study is to validate the cross-layer design for DSRC and is fundamentally different to that of the message scheduling and congestion control algorithm presented as a part of the SAE-J2945.1 standard. The complexity verification and results of analysis show the proposed controller is an efficient and fair design.