Network Availability Maximization for Free-Space Optical Satellite Communications

This letter considers availability maximized ground station (GS) selection for free-space optical (FSO) satellite networks, which is a challenging problem in the area of optical satellite communications. As a main contribution of this letter, we propose to address this problem from a new perspective of mathematical optimization. In particular, we advocate a gradient projection based algorithm after performing smoothing and relaxation on the original problem. Simulation results and complexity analysis show that, when compared to the conventional GS selection methods, the proposed scheme achieves a better tradeoff between network availability and computational complexity.

I. Introduction

Free-space optical (FSO) communications have attracted a lot of attention in both academia and industry. As an appealing advantage, FSO communications can achieve much higher data rates than conventional radio frequency (RF) communications since the optical band provides much broader bandwidth. On the other hand, the required data rates in modern satellite communications, e.g., in feeder links of geostationary Earth orbit (GEO) satellites, have been increasing tremendously. Among practical wireless solutions, FSO communications have turned out to be promising for next-generation high-speed satellite networks [1]. For instance, the relay link from low Earth orbit (LEO) to GEO in the European Data Relay System (EDRS) has been implemented via optical communications [2]. Moreover, different applications of FSO communications to LEO downlinks and GEO feeder links have been reported in [3]–[6] and [7]–[10], respectively.