The medium access control (MAC) protocol of IEEE 802.11p dedicated to vehicular ad hoc networks (VANETs) employs carrier sense multiple access with collision avoidance (CSMA/CA) with distributed coordination function (DCF) which prohibits simultaneous transmissions in the same detection area in order to avoid possible interference and collision between neighboring vehicles. This prohibition results in temporary blocking of data reception, which reduces the average network throughput. To solve this problem, we propose a physical (PHY)/MAC cross-layer design based on transmit antenna selection (TAS) and transmit power adaptation (TPA). We consider spatial multiplexing zero-forcing Bell-labs layered space-time (ZF-VBLAST) over multiple-input and multiple-output (MIMO) time-varying flat fading channel to be implemented in vehicle-to-vehicle (V2V) communication. The cross-layer approach is implemented to get the maximal network throughput on the MAC layer by using the channel state information (CSI) obtained from the PHY layer, while the MIMO spatial multiplexing technique is used to increase the spectral efficiency. This design helps transmitters to select the best combination of transmitting antennas to maximize throughput and also to choose the adequate transmit power level to minimize neighbors' interference and collision. Also, this solution comes with a multi-user interference cancellation method that allows simultaneous transmissions as long as the sum of transmit antennas within the same radio range does not exceed the number of receive antennas. This paper evaluates the proposed cross-layer architecture by calculating the average network throughput per V2V links concerning different network parameters such as the number of vehicles and antennas. The simulation results show that this solution allows more vehicles to communicate simultaneously and thus significantly improves the average network throughput compared to 802.11p MAC standard, in particular for VANETs with high density.

专用于车辆自组织网络（VANET）的IEEE 802.11p的媒体访问控制（MAC）协议采用具有冲突避免功能的载波侦听多路访问（CSMA / CA）和分布式协调功能（DCF），该功能禁止在同一检测区域中同时进行传输为了避免相邻车辆之间可能发生的干扰和碰撞。此禁止导致数据接收的临时阻塞，从而降低了平均网络吞吐量。为了解决这个问题，我们提出了一种基于发射天线选择（TAS）和发射功率自适应（TPA）的物理（PHY）/ MAC跨层设计。我们考虑在车到车（V2V）通信中实现多输入和多输出（MIMO）时变平坦衰落信道上的空间复用零强迫贝尔实验室分层时空（ZF-VBLAST）。通过使用从PHY层获得的信道状态信息（CSI），实现了跨层方法以在MAC层上获得最大的网络吞吐量，而MIMO空间复用技术则用于提高频谱效率。这种设计有助于发射机选择最佳的发射天线组合，以最大程度地提高吞吐量，并选择适当的发射功率水平，以最大程度地减少邻居的干扰和冲突。也，该解决方案带有多用户干扰消除方法，只要在相同无线电范围内的发射天线总数不超过接收天线的数量，该方法便允许同时进行传输。本文通过计算有关不同网络参数（例如，车辆和天线的数量）的每条V2V链路的平均网络吞吐量，来评估提出的跨层体系结构。仿真结果表明，与802.11p MAC标准相比，该解决方案允许更多车辆同时通信，从而显着提高了平均网络吞吐量，尤其是对于高密度VANET。本文通过计算有关不同网络参数（例如，车辆和天线的数量）的每条V2V链路的平均网络吞吐量，来评估提出的跨层体系结构。仿真结果表明，与802.11p MAC标准相比，该解决方案允许更多车辆同时通信，从而显着提高了平均网络吞吐量，尤其是对于高密度VANET。本文通过计算有关不同网络参数（例如，车辆和天线的数量）的每条V2V链路的平均网络吞吐量，来评估提出的跨层体系结构。仿真结果表明，与802.11p MAC标准相比，该解决方案允许更多车辆同时通信，从而显着提高了平均网络吞吐量，尤其是对于高密度VANET。