空间信息网中的FSO/RF通信技术

 空间信息网是以多种空间平台（如同步卫星或中、低轨道卫星、平流层浮空器及有人或无人驾驶飞行器等）为载体，实时获取、传输和处理空间信息的网络系统。由于其节点种类多，通信链路状态相对复杂。调研了空间信息网通信链路传输技术，分析了空间信息网中微波射频通信（RF）、自由空间光通信（FSO）和FSO/RF混合通信技术。分析表明，星-星链路适合FSO通信，但对于受天气影响严重或定位困难的其他类型链路，FSO/RF混合通信更具有优势。提出了空间信息网中基于大数据预测的FSO/RF自适应切换通信技术的开放思路。

Survey and analysis on FSO/RF communication technologies in space information networks

Space information network (SIN) is a heterogeneous network that has multiple platforms including GEO/MEO/LEO satellites, stratosphere balloons, unmanned aerial vehicles in the backbone, and terrestrial terminals (e.g., ground stations) functioning as access nodes. The appearance of SIN realizes efficient resource sharing and utilization of distributed information within a large-scale space. Due to the diversity of network nodes, the condition of communication links in SINs is very complicated. Specifically, there are six types of SIN links:inter-satellite link, inter-aircraft link, terrestrial link, satellite-aircraft link, satellite-ground link, and aircraft-ground link. In this paper, we extensively investigate the recent advances in the field of communication links in the SIN, and analyze the research findings, especially the studies on radio frequency (RF), free space optics (FSO) and FSO/RF hybrid communication in the SIN. The analysis demonstrates that, compared with the traditional RF communication, FSO technology has high bandwidth, large capacity, and negligibly small requirement of spectral examination, at the additional cost of narrow spread, slow motion tracking, and vulnerability to bad weather. We further show that FSO is most suitable for inter-satellite links, while for the other links over atmosphere influence or rapid positioning, the FSO/RF hybrid communication has more obvious advantages. Since there have been minor efforts on the FSO/RF hybrid communication, we propose an adaptive switching mechanism for FSO/RF hybrid communication based on big data prediction.