Conference Proceeding

# Dynamic Adaptation of Joint Transmission Power and Contention Window in VANET

Dept. of Electr. & Comput. Eng., Old Dominion Univ., Norfolk, VA, USA
Vehicular Technology Conference, 1988, IEEE 38th 10/2009; DOI:10.1109/VETECF.2009.5378793 In proceeding of: Vehicular Technology Conference Fall (VTC 2009-Fall), 2009 IEEE 70th
Source: IEEE Xplore

ABSTRACT In this paper, we propose an algorithm for joint adaptation of transmission power and contention window to improve the performance of vehicular network in a cross layer approach. The high mobility of vehicles in vehicular communication results in the change in topology of the Vehicular Ad-hoc Network (VANET) dynamically, and the communication link between two vehicles might remain active only for short duration of time. In order for VANET to make a connection for long time and to mitigate adverse effects due to high and fixed transmission power, the proposed algorithm adapts transmission power dynamically based on estimated local traffic density. In addition to that, the prioritization of messages according to their urgency is performed for timely propagation of high priority messages to the destination region. In this paper, we incorporate the contention based MAC protocol 802.11e enhanced distributed channel access (EDCA) mechanism to implement a priority-based vehicle-to-vehicle (V2V) communication. Simulation results show that the proposed algorithm is successful in getting better throughput with lower average end-to-end delay than the algorithm with static/default parameters.

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ABSTRACT: Broadcasting is a common operation in a network to resolve many issues. In a mobile ad hoc network (MANET) in particular, due to host mobility, such operations are expected to be executed more frequently (such as finding a route to a particular host, paging a particular host, and sending an alarm signal). Because radio signals are likely to overlap with others in a geographical area, a straightforward broadcasting by flooding is usually very costly and will result in serious redundancy, contention, and collision, to which we call the broadcast storm problem. In this paper, we identify this problem by showing how serious it is through analyses and simulations. We propose several schemes to reduce redundant rebroadcasts and differentiate timing of rebroadcasts to alleviate this problem. Simulation results are presented, which show different levels of improvement over the basic flooding approach.
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##### Conference Proceeding: Priority Based Inter-Vehicle Communication in Vehicular Ad-Hoc Networks using IEEE 802.11e
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ABSTRACT: In this paper, we study the use of IEEE 802.11e for priority based safety messaging for inter-vehicle communications (IVC) in vehicular ad-hoc networks (VANET). The message priorities, which are assigned based on message urgency, are associated with different quality of service in terms of average delay and normalized throughput. We investigate the use of IEEE 802.11e to provide priority based service differentiation. To increase the communication reliability we also apply a repetitive transmission mechanism that provides proportional reliability differentiation for each prioritized message. We evaluate the performance of our proposed protocol using OPNET Modeler, in terms of average delay and normalized throughput as a function of the number of repetitions, number of vehicles, bit error rates, data rates, percentage of priority 1 vehicles and packet size. The results show that using proper parameter setting for IEEE 802.11e and appropriate number of repetitions per priority class will result in an efficient solution for IVC that supports different priority safety messaging.
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