Multiuser MIMO Concept for Physical Layer Security in Multibeam Satellite Systems

In satellite communication downlinks, physical layer security is challenging to achieve due to their broadcasting nature and Line-of-Sight channel characteristics. This paper provides a precoding algorithm to secure the downlinks of multiple users against multiple eavesdroppers with optimization of the minimum secrecy capacity. By the use of artificial noise, a positive secrecy capacity is achievable even if the number of eavesdroppers is higher than the number of beams. We demonstrate that a multiple-reflector antenna design provides a significantly higher secrecy and throughput performance when compared to a single-reflector design due to additional degrees of freedom, exhibited by the signal phases. The total vulnerability region is introduced as a new figure of merit with respect to unidentified eavesdroppers.