Controlled repetition based communication in VANETs using IEEE 802.11e

Since message content is of high importance in Vehicular Ad-hoc Networks (VANETs), we are proposing a network design with the message priority considered as the main factor. In this regard, we have used IEEE 802.11e protocol. As in VANETs, topology of network changes fast, wireless links between cars are unreliable. Moreover, in vehicular ad-hoc networks the Bit Error Rate (BER) is high. Thus, in this paper, we proposed to repeat the packets of the messages with the highest priority, to cope with the above mentioned problems. This idea also increases the reliability of messages with the highest priority. Nonetheless, repeating the packets leads to increased number of collisions. Hence, we should control the number of nodes, which broadcast the message, to decrease collisions. To evaluate our method, and find the optimum number of repetitions, we simulated several scenarios both for car-to-car and car-to-infrastructure modes.