Optimised CSMA protocol to support efficient clustering for vehicular internetworking

Abstract

Vehicular ad-hoc networks (VANETs) that support communication among vehicles can facilitate a wide range of road-safety applications. To deal with network fragmentation for low vehicular density, clusters of neighbouring vehicles can be formed. Clustering techniques also require timely commu- nications among vehicles. Despite the stringent performance requirements for the safety and clustering applications, the IEEE 802.11p standard still employs the carrier sensing medium access/collision avoidance (CSMA/CA) protocol that has a fixed contention window (CW) range for backoff. This results in significant inefficiency as vehicular density changes. This work investigates how the maximum CW size can be optimised to enhance performance based on vehicular density by exploiting the equivalence between the CSMA/CA and Aloha performance models. Simulation shows a great reduction in transmission delay for the proposed protocol when compared with the standardised one. Thus, with the low latency, the new protocol is useful to the vehicle clustering and road-safety applications.