Abstract

         In this paper, we present a new scheme for dynamic adaptation of transmission power and contention window (CW) size to enhance performance of information dissemination in Vehicular Ad-hoc Networks (VANETs). The proposed scheme incorporates the Enhanced Distributed Channel Access (EDCA) mechanism of 802.11e and uses a joint approach to adapt transmission power at the physical (PHY) layer and quality-of-service (QoS) parameters at the medium access control (MAC) layer. In our scheme, transmission power is adapted based on the estimated local vehicle density to change the transmission range dynamically, while the CW size is adapted according to the instantaneous collision rate to enable service differentiation. In the interest of promoting timely propagation of information, VANET advisories are prioritized according to their urgency and the EDCA mechanism is employed for their dissemination. The performance of the proposed joint adaptation scheme was evaluated using the ns-2 simulator with added EDCA support. Extensive simulations have demonstrated that our scheme features significantly better throughput and lower average end-to-end delay compared with a similar scheme with static parameters.

A new scheme for the dynamic adaptation of transmission power and the size of the contention window (CW) to improve the performance of the information diffusion in vehicular Ad-hoc networks (VANETs). The proposed scheme incorporates the Enhanced Distributed Channel Access (EDCA) mechanism of 802.11e and uses a joint approach to adapt the transmission power in the physical layer (PHY) and quality of service (QoS) parameters in the medium access control (MAC) layer. In our scheme, the transmission power is adapted based on the estimated local density of the vehicle to dynamically change the transmission range, while the CW size is adjusted according to the instantaneous collision speed to allow the differentiation of the service. In order to promote the timely propagation of information, VANET's notices are prioritised according to their urgency and the EDCA mechanism is used for dissemination. The performance of the proposed joint adaptation scheme was evaluated using the ns-2 simulator with the added EDCA support. Extensive simulations have shown that our scheme has significantly better performance and a lower end-to-end average compared to a similar scheme with static parameters.