Reducing collision probability with multihop diversity for vehicle-to-roadside networks

Implementation of high performance, low-latency cooperative collision avoidance (CCA) protocols for Vehicular Ad hoc NETworks (VANETs) is of major importance for public safety organizations and automobile manufacturers. In this study, we examine a vehicle-to-roadside (V2R) transmission scheme in which the intermediate roadside terminal amplifies and forwards the broadcasted warning signal and acts as a relay to provide diversity to the destination vehicle. We compare the bit-error-rate (BER) and packet-error-rate (PER) performances of multihop V2R and single-hop vehicle-to-vehicle (V2V) transmission schemes. We further present a Markov chain traffic model in order to observe the impact of the improved error-rate performance on the collision probability. We assume the inter-vehicle spacing follows exponential distribution, and then draw a stochastic model considering the probabilities of successful message reception, transmission delay and drivers´ reaction time. Numerical results reveal that the chance of collision in the V2R scheme is considerably less than the single-hop V2V case for equal message sizes sent over a large range of inter-vehicle spacing. This setting plays a vital role in wireless intervehicle warning applications such as collision avoidance for automated and semiautomated highway systems.