This paper presents an optimization approach for cooperative Medium Access Control (MAC) techniques in Vehicular Ad Hoc Networks (VANETs) equipped with Roadside Unit (RSU) to enhance network throughput. Our method employs a distributed cooperative MAC scheme based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol, featuring selective RSU probing and adaptive transmission. It utilizes a dual timescale channel access framework, with a ``large-scale'' phase accounting for gradual changes in vehicle locations and a ``small-scale'' phase adapting to rapid channel fluctuations. We propose the RSU Probing and Cooperative Access (RPCA) strategy, a two-stage approach based on dynamic inter-vehicle distances from the RSU. Using optimal sequential planned decision theory, we rigorously prove its optimality in maximizing average system throughput per large-scale phase. For practical implementation in VANETs, we develop a distributed MAC algorithm with periodic location updates. It adjusts thresholds based on inter-vehicle and vehicle-RSU distances during the large-scale phase and accesses channels following the RPCA strategy with updated thresholds during the small-scale phase. Simulation results confirm the effectiveness and efficiency of our algorithm.

翻译：本文针对配备路侧单元（RSU）的车载自组织网络（VANETs），提出了一种协作介质访问控制（MAC）技术的优化方法，以提升网络吞吐量。该方法基于载波侦听多点接入/冲突避免（CSMA/CA）协议，采用分布式协作MAC方案，具备选择性RSU探测与自适应传输功能。其利用双时间尺度信道接入框架：“大尺度”阶段适应车辆位置的渐进变化，“小尺度”阶段适应快速信道波动。我们提出了RSU探测与协作接入（RPCA）策略——一种基于车辆间动态距离（相对于RSU）的两阶段方法。运用最优序贯计划决策理论，严格证明了该策略在最大化每个大尺度阶段平均系统吞吐量方面的最优性。针对VANETs的实际部署，我们开发了带周期性位置更新的分布式MAC算法：在大尺度阶段根据车辆间及车辆-RSU距离调整阈值，在小尺度阶段按更新阈值后的RPCA策略接入信道。仿真结果验证了该算法的有效性与高效性。