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

在AY 2022中，我们提出了一种基于纠缠的新型FSO/QKD系统，该系统使用LEO和GEO卫星。利用低地球轨道（LEO）卫星和EB方案的FSO/QKD系统已经被提出。LEO卫星受益于低信道损耗;然而，其覆盖范围有限。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的关键速率。因此，结合GEO和LEO卫星成为全球规模QKD网络的一个有前途的解决方案。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网络提供了可能。基于所提出的系统的设计标准，我们研究了日本QKD网络使用现有的GEO卫星和LEO卫星星座为日本的合法用户提供QKD服务的案例研究的可行性。在此基础上，基于发射机和接收机的设计准则，研究了该系统在非授权接收机攻击（URA）和波束分裂攻击（BSA）下的密钥性能。特别是，我们的目标是设计传输的信号，以防止URA，并提出了一个简单的方案，允许合法用户检测BSA。此外，我们还研究了与卫星FSO系统设计和应用相关的问题，包括FSO/RF混合系统、差错控制以及采用先进的混合ARQ技术的改进。

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.