Free space optical communication has been applied in many scenarios because of its security, low cost and high rates. In such scenarios, a tracking system is necessary to ensure an acceptable signal power. Free space optical links were considered unable to support fast moving nodes, such as unmanned aerial vehicles, cars or pedestrians, in optical mobile communication because existing tracking schemes fail to track the nodes accurately and rapidly. In this paper, we propose a novel tracking system exploiting multiple beacon lasers. Each beacon laser’s power is measured to estimate the orientation of the target. Unlike existing schemes which drive servo motors multiple times based on consecutive measurements and feedback, our scheme can directly estimate the next optimal targeting shift for the servo motors based on a single measurement, allowing the tracking system to converge much faster. Closed-form outage probability expression is derived for the optical mobile communication system with ideal tracking, where pointing error and moving statistics are considered. To maintain sufficient average power and reduce the outage probability, the recommended beam divergence of the main laser is expressed in closed form as a function of the target’s statistics of random shift, providing insights to the system design.

中文翻译：

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光移动通信中快速移动节点的跟踪系统及设计规则

自由空间光通信由于其安全性，低成本和高速率而已被应用在许多情况下。在这种情况下，必须使用跟踪系统以确保可接受的信号功率。自由空间光链路被认为无法在光移动通信中支持快速移动的节点，例如无人驾驶飞机，汽车或行人，因为现有的跟踪方案无法准确，快速地跟踪节点。在本文中，我们提出了一种利用多个信标激光器的新型跟踪系统。测量每个信标激光器的功率以估计目标的方向。与现有的基于连续测量和反馈多次驱动伺服电机的方案不同，我们的方案可以基于一次测量直接估算伺服电机的下一个最佳目标位移，使跟踪系统收敛更快。对于具有理想跟踪的光移动通信系统，推导了闭式故障概率表达式，其中考虑了指向误差和移动统计量。为了保持足够的平均功率并减少中断可能性，建议将主激光器的推荐光束发散度以封闭形式表示，这取决于目标的随机位移统计量，从而为系统设计提供了见识。