A contention window adaptation broadcast protocol in VANETs under differentiating transmission and virtual slot periods

Designing an efficient broadcast protocol is remarkably critical to disseminate safety information in Vehicular Ad hoc Networks (VANETs). It is essential to take low network traffic into account when depicting VANETs broadcast communication with Markov chain, especially in sparse network. Besides, network performance becomes poor due to packets collision under heavy traffic situation while standard broadcast protocol is adopted in VANETs. To address the above problems, we consider the influence that the difference of transmission and virtual slot periods makes an impact on network performances, when Markov chain is introduced to describe network model. Then we define three kinds of network communication states aiming at adjusting Contention Window (CW). Finally, we introduce a CW adaptation broadcast protocol to improve packet delivery ratio and throughput. The performance of the proposed protocol is evaluated using NS3, and simulation results have shown that our proposed protocol is the most effective and have the best performance compared to the traditional one.