Abstract:

Safe and efficient operation of the vehicle is affected by the accuracy of the information in Cooperative Vehicle Infrastructure Environment. In order to reduce the occurrence of the channel conflict of information interaction process in Cooperative Vehicle Infrastructure Environment, the IEEE 802.11p’s channel access protocol and the mechanism of Enhanced Distributed Channel Access (EDCA) are studied. And the traditional EDCA model protocol’s handshake mechanism and RTS and CTS control frames’ content are optimized. In addition, the back off algorithm of contention window of CVIS is designed. then a more reasonable adaptive back off algorithm which can reflect traffic characters based on contention window is proposed, and it’s called ATEDCA. In order to verify and compare the communication performance of ATEDCA and EDCA in CVIS, three simulation scenarios are designed in OPNET Modeler and they are scenario of different vehicle densities, scenario of different transmission distances and scenario of different vehicle velocities. The results indicate that ATEDCA’s transmission delay decreased by 10.1% compared to EDCA and its throughput increased by 7.5% compared to EDCA, and the back off slots of ATEDCA decreased by 30.6% than EDCA’s in standard scenario. All in all, ATEDCA can reduce the likelihood of message channel conflict effectively.

Key words: intelligent transportation, ATEDCA, back off algorithm, channel access protocol

摘要：

在车路协同环境中信息交互的准确性直接影响到车辆的安全高效运行.为了 减少车路协同信息交互数据信道冲突的发生，本文通过分析IEEE 802.11p 和EDCA信道 接入机制，优化EDCA协议的握手机制、RTS和CTS控制帧内容，形成了具有交通特性的 ATEDCA信道接入协议，提出了适用于具有交通特性的竞争窗口退避算法，并且设计了 车路协同通信评估模型.通过设计不同车辆密度、不同节点传输距离及不同车辆行驶速度 的仿真场景，在OPNET Modeler 中进行仿真，比较ATEDCA与EDCA对车路协同系统通 信性能的影响.结果表明：相同场景下，在传输延时方面，ATEDCA 较EDCA 减少了 10.1%；在吞吐量方面，ATEDCA较EDCA增加了7.5%；在退避时隙数量方面，ATEDCA 较EDCA减少了30.6%.因此，ATEDCA可以更好地减少消息信道冲突的发生.

关键词: 智能交通, ATEDCA, 退避算法, 信道接入协议