Recent developments in intelligent transportation system (ITS) require a reliable medium access control (MAC) protocol to support the high-priority safety message broadcast. The rapid increase in spectrum demand is addressed by implementing cooperation in cognitive radio-based vehicular ad-hoc networks (CR-VANETs). In this paper, a novel cooperative MAC for CR-VANET (CCRV-MAC) is proposed for safety applications. CCRV facilitates collaboration among vehicles to exchange channel status reports for pro-active channel switching in the case of primary user (PU) appearance. Additional control signals are introduced to enable transmission mode selection. The helper nodes rebroadcast failed transmission by employing the proposed cooperative makeup strategy. The protocol is modelled using a Markov chain and is analyzed for various performance parameters using NS-2. It is also compared with two existing MAC protocols. In the results, CCRV shows enhanced throughput and packet delivery ratio. The average delay in CCRV MAC is reduced by approximately 37% compared to existing cognitive radio network (CRN) and vehicular ad-hoc network (VANET) based MAC approaches. Analysis of overhead and delay illustrates the reliability of CCRV as it suffers a maximum average delay of 69 ms under adverse conditions which is well below the permissible limit of 100 ms.

智能运输系统（ITS）的最新发展要求可靠的媒体访问控制（MAC）协议来支持高优先级安全消息广播。通过在基于认知无线电的车载自组织网络（CR-VANET）中实施合作，可以解决频谱需求的快速增长。在本文中，为安全应用提出了一种新型的CR-VANET协同MAC（CCRV-MAC）。CCRV有助于车辆之间的协作，以交换通道状态报告，以便在出现主要用户（PU）时主动进行通道切换。引入了其他控制信号以启用传输模式选择。通过使用建议的协作组成策略，辅助节点重新广播传输失败。该协议使用马尔可夫链进行建模，并使用NS-2分析各种性能参数。还将它与两个现有的MAC协议进行比较。结果表明，CCRV显示出更高的吞吐量和数据包传输率。与现有的基于认知无线电网络（CRN）和基于车辆自组织网络（VANET）的MAC方法相比，CCRV MAC的平均延迟减少了约37％。开销和延迟的分析说明了CCRV的可靠性，因为在不利条件下CCRV的最大平均延迟为69 ms，该延迟大大低于100 ms的允许限制。与现有的基于认知无线电网络（CRN）和基于车辆自组织网络（VANET）的MAC方法相比，CCRV MAC的平均延迟减少了约37％。开销和延迟的分析说明了CCRV的可靠性，因为在不利条件下CCRV的最大平均延迟为69 ms，该延迟大大低于100 ms的允许限制。与现有的基于认知无线电网络（CRN）和基于车辆自组织网络（VANET）的MAC方法相比，CCRV MAC的平均延迟减少了约37％。开销和延迟的分析说明了CCRV的可靠性，因为在不利条件下CCRV的最大平均延迟为69 ms，该延迟大大低于100 ms的允许限制。