Contention-based carrier sense multiple access (CSMA) and contention-free time division multiple access (TDMA) protocol are two typical access protocols of media access control in vehicular ad hoc network (VANET). They all show their unique advantages under specific conditions. TDMA has high transmission reliability, CSMA has a low transmission delay in the communication environment with low packet arrival rate. However, when the arrival rate of information packets increases rapidly, the throughput of CSMA will decrease rapidly and approach zero, which is not suitable for data transmission in the communication environment with a high arrival rate of information packets; while data transmission through a single TDMA protocol will cause high system overhead due to strict synchronous information. Aiming at the defects of the two protocols and the multi-channel communication environment, this study proposes the optimised protocol model multi-priority time division-CSMA (MPTD-CSMA). The optimised protocol model not only ensures the reliability of data communication but also reduces the transmission delay of the system. At the same time, the multi-priority mechanism is added to increase the channel utilisation of the protocol model.

中文翻译：

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VANET中基于现场可编程门阵列的MPTD-CSMA协议的硬件实现和性能分析

基于竞争的载波侦听多路访问（CSMA）和无竞争的时分多路访问（TDMA）协议是车载媒体访问控制的两种典型访问协议 特别指定网络（VANET）。它们都在特定条件下显示出其独特的优势。TDMA具有较高的传输可靠性，而CSMA在通信环境中具有较低的传输延迟，且数据包到达率较低。但是，当信息包到达率快速增加时，CSMA的吞吐量将迅速下降并趋于零，这不适合信息包到达率高的通信环境中的数据传输。由于严格的同步信息，通过单个TDMA协议进行数据传输会导致较高的系统开销。针对这两种协议以及多通道通信环境的缺陷，提出了一种优化的协议模型多优先级时分CSMA（MPTD-CSMA）。优化的协议模型不仅保证了数据通信的可靠性，而且减少了系统的传输延迟。同时，添加了多优先级机制以提高协议模型的信道利用率。