Reconfiguration Penalty-Aware Topology Control in Optical Communication Satellite Networks

Optical communication satellite networks (OC-SN s) are promising candidates for the next-generation high-throughput space networks, and are driven by free space optical (FSO) communication technology. While FSO has a great advantage of efficient data transmission using a collimated narrow beam, it requires accurate pointing, acquisition and tracking that lead to long topology-reconfiguration time. In particular, from practical networking viewpoint, it is essential to discuss the impact of such topology-reconfiguration penalty on throughput, however, this problem has not yet been considered in the design of OCSNs. Therefore, this paper proposes a recon-figuration frequency-controllable dynamic-topology model and investigated the relationship between topology-reconfiguration and network throughput. The results indicate that properly suppressing reconfiguration improves throughput by about 10% compared with the conventional model. It was also found that too much reconfiguration suppression leads to a significant loss in important topological features and, conversely, to throughput degradation. These results provide important insight into the nature of the system: The dynamic topology control of OCSNs is not a trivial problem of simply suppressing reconfiguration, but rather a problem of finding the optimal point where important topology characteristics and reconfiguration frequency are well balanced.

I. Introduction

Free space optical (FSO) communication is a key technol-ogy for high-throughput space networks, and optical commu-nication satellite networks (OCSNs) has been proposed [1]. Along with the recent development of high-altitude platform station (HAPS) technology, a high-throughput OCSN is be-coming more feasible. For example, research on HAPS-based satellite-air-ground (SAG) systems will overcome the FSO's disadvantages of atmospheric fluctuations and susceptibility to shielding. Sharma et al. [2] proposed a high-throughput SAG system with long visibility time (large zenith angle) between satellite and ground station by adopting a hybrid configuration with satellite-to-air FSO and air-to-ground radio-frequency (RF) links. More challenging study [3] proposed a terabit-per-second SAG system with an all-optical configuration.