VANET中基于公平性的多信道MAC协议

随着车载无线通信需求的增加，车载自组织网络（VANET）将成为现代智能交通系统的一个重要组成部分。对VANET中多信道MAC层协议进行了研究，提出了一种提升网络公平性的退避算法。车辆通过比较自身已成功发送的业务量与平均业务量的大小，确定不同的退避方案，一定程度上实现网络中车辆的接入公平。考虑到该退避算法在提升公平性的同时，牺牲了一定的网络吞吐量，服务信道不饱和，进一步提出根据车辆密度调整服务预约时期长度的算法，提高服务信道的利用率，增大网络的吞吐量。仿真结果表明，提出的退避算法公平性指数相比于二进制退避算法，提升了约2.3倍，而相比于倍数增线性减退避算法，提升了约2.05倍，网络的吞吐量提高了约16%。

Multichannel MAC protocol based on fairness in VANET

With the increasing of vehicular wireless communication, vehicle ad hoc networks (VANETs) have become an important part of the Intelligent Transportation System. Based on the multi-channel MAC protocol in VANETs, this paper proposed a backoff algorithm for different nodes considering fairness of network. By comparing the successful sending traffic throughput of the node and the average traffic throughput for its neighbors, the node determined backoff windows so that to improve the fairness in accessing process. In order to improve the fairness of network, the algorithm sacrificed amount of traffic throughput. Noticed that the service channels are not saturated, this paper also proposed an algorithm to adjust the length of service reservation period based on node density. The algorithm improved the utilization of service channels and the throughput of network. Simulation results indicated that comparing with the BEB algorithm and the MILD algorithm, the proposed backoff algorithm can effectively improve fairness of network by 2.3 times and 2.05 times, respectively. Meanwhile, the adjusting algorithm can significantly improve the network throughput by 16%.