Network Status Detection-Based Dynamic Adaptation of Contention Window in IEEE 802.11p

In recent years the research on Vehicular Ad Hoc Network (VANET) has been paid much attention due to the development of wireless network becoming mature, people think highly of traffic safety issue, the popularity of Global Positioning System (GPS), promising applications of VANET being exploited. However, VANET has the essential property of rapid change of large scale network topology. Besides, the vehicles distributed over the road usually causes serious signal collisions and interferences. Thus, it calls for special concern to deal with the performances of throughput, collision and delay. In this paper we propose a Detection-Based MAC mechanism by modifying RTS/CTS to detect network congestion through message exchange and predict number of competing nodes. Both these information is used to dynamically adjust contention window size. Simulations focus on the MAC layer of IEEE 802.11p and the results show that the proposed method is able to effectively increase overall throughput, reduce packet collision rate and delay time.