Robust secure beamforming design in cognitive satellite communication for coexistence with terrestrial networks

This paper examines the scope of physical layer security (PLS) enabled in cognitive satellite communication for co-existence with terrestrial networks. The primary concern is to ensure secure information transmission from a Satellite Earth Station to a GEO Satellite while safeguarding against potential eavesdropping from a Spacecraft. To this end, an optimization problem is formulated, considering the inherent imperfections in the channel state information (CSI). The aim is to maximize the achievable secrecy rate while adhering to specific constraints on transmit power and interference at the nearby Fixed Service transmitter. This optimization task involves fine-tuning the beamforming vectors at the Satellite Earth Station transmitter. Due to the mathematical complexity of the formulated problem, the Semidefinite Relaxation (SDR) technique is employed. This conversion technique transforms the initial non-convex problem into a tractable one, allowing the derivation of beamforming weight vectors. Finally, simulation results are presented to confirm the effectiveness of the robust beamforming scheme. To the best of our knowledge, this study potentially marks the first attempt at developing a robust, secure beamforming strategy for uplink transmission in the forthcoming era of satellite communications. Its aim is to enable spectral coexistence with nearby terrestrial networks.