On the Use of HAPS to Increase Secrecy Performance in Satellite Networks

TL;DR

This paper explores how using a high altitude platform station (HAPS) as a relay in satellite communications can enhance secrecy against RF eavesdropping, with analytical expressions for secrecy performance and design insights.

Contribution

It introduces a novel HAPS-assisted satellite communication scheme combining FSO and RF links and derives closed-form secrecy metrics for the first time.

Findings

HAPS relaying improves secrecy performance in satellite links.

Pointing errors and shadowing significantly affect secrecy metrics.

Design guidelines for secure satellite-HAPS-ground networks are provided.

Abstract

In this paper, we investigate the secrecy performance of radio frequency (RF) eavesdropping for a high altitude platform station (HAPS) aided satellite communication (SatCom) system. More precisely, we propose a new SatCom scheme where a HAPS node is used as an intermediate relay to transmit the satellite's signal to the ground station (GS). In this network, free-space optical (FSO) communication is adopted between HAPS and satellite, whereas RF communication is used between HAPS and GS as the line-of-sight (LoS) communication cannot be established. To quantify the overall secrecy performance of the proposed scheme, closed-form secrecy outage probability (SOP) and the probability of positive secrecy capacity (PPSC) expressions are derived. Moreover, we investigate the effect of pointing error and shadowing severity parameters. Finally, design guidelines that can be useful in the design of practical SatCom networks are presented.