车对车（V2 V）通信网络通过定期广播基本安全消息（BSM）或\textit{safety beacons}来实现安全应用。信标包括时间关键信息，如发送方车辆的位置、速度和方向。在某些场景中，车辆密度可能非常高，并且这种V2 V网络遭受信道拥塞和不期望的分组冲突水平;这进而可能严重危及安全应用可靠性并导致冲突风险情况。在这项工作中，我们进行实验分析的安全应用程序的可靠性（在\textit{collision risks}方面），并得出结论，存在一个独特的信标率的安全性能最大化，这个速率是唯一的不同的车辆密度。使用简单的基于运动学的模型来计算特定车辆的碰撞风险，并且该模型基于\textit{tracking error}，该\textit{tracking error}被定义为车辆的实际位置与其邻居（经由最近的信标）感知到的该车辆的位置之间的差。此外，我们分析了碰撞风险和两个著名的网络性能指标，\textit{Age of Information}（AoI）和\textit{throughput}之间的互连。我们的实验表明，AoI有很强的相关性与碰撞风险和AoI的最佳信标率是类似的安全最佳信标率，无论车辆密度，排队大小和纪律。而吞吐量只有在较高的车辆密度下才能很好地工作。
英文摘要：
Vehicle-to-Vehicle (V2V) communication networks enable safety applications via periodic broadcast of Basic Safety Messages (BSMs) or \textit{safety beacons}. Beacons include time-critical information such as sender vehicle's location, speed and direction. The vehicle density may be very high in certain scenarios and such V2V networks suffer from channel congestion and undesirable level of packet collisions; which in turn may seriously jeopardize safety application reliability and cause collision risky situations. In this work, we perform experimental analysis of safety application reliability (in terms of \textit{collision risks}), and conclude that there exists a unique beacon rate for which the safety performance is maximized, and this rate is unique for varying vehicle densities. The collision risk of a certain vehicle is computed using a simple kinematics-based model, and is based on \textit{tracking error}, defined as the difference between vehicle's actual position and the perceived location of that vehicle by its neighbors (via most-recent beacons). Furthermore, we analyze the interconnection between the collision risk and two well-known network performance metrics, \textit{Age of Information} (AoI) and \textit{throughput}. Our experimentation shows that AoI has a strong correlation with the collision risk and AoI-optimal beacon rate is similar to the safety-optimal beacon rate, irrespective of the vehicle densities, queuing sizes and disciplines. Whereas throughput works well only under higher vehicle densities.
Safety Message Power Transmission Control for Vehicular Ad hoc Networks
车载自组网是移动自组网中最具挑战性的研究领域之一。在本研究中，我们提出了一个动态功率调整的协议，将用于发送周期性的安全消息。（信标）基于取决于信道拥塞和用于传输的功率的信道状态的分析。信标功率控制（Beacon Power Control，BPC）协议首先检测信道拥塞的百分比，根据检测结果调整安全消息的发送功率，使其达到最佳功率。这将导致减少信道中的拥塞，并实现良好的信道性能和信标传播。
