Evolution and accessibility of smart-phones have led to a huge demand in network bandwidth. The ubiquitous use of smart-phones in high-speed trains poses a unique challenge in delivering high-speed internet service on board. This challenge can be overcome by employing free-space optics, an alternative to radio-frequency technology. Previous coverage models for ground–train communications employed single laser systems with a larger divergence angle to cover a larger distance. Larger divergence angles lead to larger geometric losses, which may result in a non-reliable communication link. This study proposes a sectorised multi-beam coverage model with a smaller divergence angle to reduce the impact of geometric losses in the system. This study also proposes two receiver (Rx) architectures for Rxs deployed on the train. Along with geometric losses, the atmospheric attenuation is taken into consideration for the FSO link. The performance of the ground–train communications system in terms of bit-error-rate is evaluated under weak turbulence conditions via numerical simulation.

中文翻译：

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用于FSO地面对火车通信的分段基站

智能电话的发展和可访问性导致对网络带宽的巨大需求。在高速列车中无处不在使用智能手机给车载高速互联网服务提出了独特的挑战。可以通过采用自由空间光学技术（射频技术的替代方法）来克服这一挑战。以前的地面列车通信覆盖模型使用的单激光系统具有较大的发散角，可以覆盖较大的距离。较大的发散角会导致较大的几何损耗，这可能会导致通信链路不可靠。这项研究提出了一种具有较小发散角的扇形多波束覆盖模型，以减少系统中几何损耗的影响。这项研究还针对列车上部署的Rx提出了两种接收器（Rx）架构。随着几何损失，FSO链路考虑了大气衰减。通过数值模拟评估了在弱湍流条件下地面列车通信系统的误码率性能。