Theoretical Performance Analysis of Vehicular Broadcast Communications at Intersection and their Optimization

Cooperative vehicle safety (CVS) systems are a key application of intelligent transportation systems. In CVS systems, vehicles periodically broadcast their information, e.g., position, speed, and braking status. In this paper, we theoretically analyze the performance of vehicle-to-vehicle (V2V) broadcast communications at an intersection and provide tractable formulae of performance metrics to optimize them. We consider a model in which locations of vehicles are modeled separately as queueing and running segments and derive key performance metrics of V2V broadcast communications via a stochastic geometry approach. However, these theoretical expressions are highly complex and mathematically intractable, so we developed closed-form approximate formulae for them. In our approximation, the probability of successful transmission decreases geometrically as the distance to a receiver increases and is expressed by only system parameters. Using the approximate formulae, we propose a method for optimizing the broadcast rate of vehicles such that the mean number of successful receivers per unit time is maximized. Because of the closed form approximation, the optimal rate can be used as a guideline for a real-time control-method, which is not achieved through time-consuming simulations. We evaluated our approximation and optimization method through simulations and numerical experiments and found that the approximate formulae fitted well to exact analysis in a realistic setting. We also demonstrated the effectiveness of optimizing the broadcast rate.