Satellite-based Free-Space Optical Quantum Key Distribution (QKD) Systems for Secured Wireless Networks

在AY2022中，我们致力于提出一种新型的基于纠缠的FSO/QKD系统，该系统使用LEO和GEO卫星。利用近地轨道（LEO）卫星和EB方案的FSO/QKD系统已经被提出。低轨道卫星得益于低信道损耗；然而，它的覆盖面是有限的。虽然高度为35,786公里的地球同步卫星（GEO）卫星可以解决覆盖问题，但该系统存在高路径损耗和有限密钥速率的问题。因此，将地球同步轨道卫星与近地轨道卫星相结合成为全球规模QKD网络的一种很有前景的解决方案。在我们的提案中，我们专注于设计一个可以支持多个无线用户的系统，这为建立全球规模的QKD网络开辟了潜力。基于所提出系统的设计标准，我们以日本QKD网络为例，研究了利用现有的GEO卫星和LEO卫星星座为日本合法用户提供QKD服务的可行性。此外，在考虑未授权接收机攻击（URA）和分束攻击（BSA）的情况下，基于发送端和接收端的设计准则，研究了该系统的密钥性能。特别是，我们的目标是设计传输信号以防止市建局，并提出一个简单的方案，使合法用户能够检测到BSA。此外，我们还研究与卫星FSO系统的设计和应用有关的问题，包括FSO/RF混合系统，误差控制和使用先进的混合ARQ技术进行改进。

In the AY2022, we work on the proposal of a novel entanglement-based FSO/QKD system that uses LEO and GEO satellites. FSO/QKD systems using low-Earth orbit (LEO) satellites and EB scheme have been proposed previously. The LEO satellite benefits from the low channel loss; however, its coverage is limited. While a geosynchronous satellite (GEO) satellite with an altitude of 35,786 km can solve the coverage problem, the system suffers from a high path loss and limited key rates. Therefore, combining GEO and LEO satellites becomes a promising solution for the global-scale QKD network. In our proposal, we focus on designing a system that can support multiple wireless users, which opens the potential to establish a global-scale QKD network. Based on the design criteria for the proposed system, we investigate the feasibility of a case study for the Japan QKD network using the existing GEO satellite and LEO satellite constellation to provide QKD service for legitimate users in Japan. Furthermore, the secret key performance of the proposed system is studied based on the design criteria of transmitters and receivers considering the unauthorize receiver attack (URA) and beam-splitting attack (BSA). In particular, we aim to design the transmitted signal to prevent URA and propose a simple scheme that allows legitimate users to detect BSA. Besides, we work on issues related to the design and applications of satellite based FSO systems, including hybrid FSO/RF systems, error control and improvement using advanced hybrid ARQ technique.