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Issue No. 09 - September (2011 vol. 22)
ISSN: 1045-9219
pp: 1528-1535
Danda B. Rawat , Old Dominion University, Norfolk
Dimitrie C. Popescu , Old Dominion University, Norfolk
Gongjun Yan , Indiana University Kokomo, IN
Stephan Olariu , Old Dominion University, Norfolk
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.
Vehicular networks, VANETs, broadcast, contention window adaptation, message differentiation, transmission power adaptation, QoS, medium access control protocol, 802.11e EDCA, intelligent transportation system.

G. Yan, D. C. Popescu, S. Olariu and D. B. Rawat, "Enhancing VANET Performance by Joint Adaptation of Transmission Power and Contention Window Size," in IEEE Transactions on Parallel & Distributed Systems, vol. 22, no. , pp. 1528-1535, 2011.
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