Vehicular ad hoc network as an intelligent transportation system supports traffic management to facilitate navigation, safety, and services to end-users. Delivery of safety messages is prioritized to avoid hazards in the system. In this regard, this paper discusses the existing TDMA MAC protocols in vehicular ad hoc network that efficiently coordinates and communicates with the vehicles and minimize the message collision. Vehicular movement and traffic density lead to link failures, collisions, and load imbalance in the network. MAC protocols with dynamic time slot synchronization, message priority, bandwidth, and frequency management techniques ensure safe message delivery, hazard prevention, and low message collision rates in VANETs. This article provides the classification of TDMA MAC protocols for distributed, centralized and hybrid protocols. Various types of collisions, two-way traffic load, multi-channel utilization, and access challenges are discussed in detail. Further, the working mechanism and performance attributes of TDMA MAC protocols are explained.

车载自组织网络作为一种智能交通系统，可支持交通管理，以促进导航，安全和为最终用户提供服务。优先发送安全消息，以避免对系统造成危害。在这方面，本文讨论了车辆自组织网络中现有的TDMA MAC协议，该协议可以有效地与车辆进行协调和通信，并最大程度地减少消息冲突。车辆的移动和流量密度导致网络中的链路故障，冲突和负载不平衡。具有动态时隙同步，消息优先级，带宽和频率管理技术的MAC协议可确保VANET中的安全消息传递，危险预防和低消息冲突率。本文为分布式，集中式和混合协议提供了TDMA MAC协议的分类。详细讨论了各种类型的冲突，双向流量负载，多通道利用率和访问挑战。进一步说明了TDMA MAC协议的工作机制和性能属性。