Improving Performance by a Dynamic Adaptive Success-Collision Backoff Algorithm for Contention-Based Vehicular Network

The distributed coordination function (DCF) is the core of the IEEE 802.11 standard and is applied routinely to contention-based vehicular networks. Many existing backoff algorithms based on DCF are applied to develop the performance of wireless networks and most of them work in saturated traffic load conditions, which are unlikely to be valid in practical wireless network. The study of the backoff algorithm under unsaturated traffic load conditions is still an open issue. In this paper, a dynamic adaptive success-collision (DASC) backoff algorithm is proposed to improve the performance of contention-based vehicular network. As we know that the probability of collision reflects system performance, and the probability of collision is restricted by the variation of contention window (<inline-formula> <tex-math notation="LaTeX">$CW$ </tex-math></inline-formula>) size and it depends on the traffic loads. A threshold is defined to judge the low or high traffic loads. In addition, the DASC backoff algorithm takes proactive measures to optimize throughput and delay through decreasing <inline-formula> <tex-math notation="LaTeX">$CW$ </tex-math></inline-formula> after “<inline-formula> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula>” times consecutive successful transmissions and increasing <inline-formula> <tex-math notation="LaTeX">$CW$ </tex-math></inline-formula> after “<inline-formula> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula>” times consecutive collisions. The simulation results indicate that the proposed DASC backoff algorithm provides better performance in terms of throughput and delay than dynamic control backoff time algorithm, exponential linear backoff algorithm, and binary exponential backoff algorithm.