Robust Beamforming Design for RHS-Enhanced Uplink Covert Satellite Communications
In this paper, we propose a robust beamforming algorithm for reconfigurable holographic surface (RHS)-enhanced uplink covert satellite communication systems. Specifically, the jamming signal is utilized to confuse multiple eavesdropping satellites. We derive the minimum detection error probability (DEP) and the optimal noise parameters to maximize the ability of noise to mask covert transmission. Under this paradigm, we formulate a covert sum rate maximization problem by jointly optimizing the digital beamforming and holographic radiation coefficient while satisfying the transmit power budget, covertness constraints, and radiation coefficient constraints. The problem is inherently non-convex and presents challenges due to the imperfect channel state information (CSI) and the high coupling among variables. Hence, we transform the original non-convex problem into a series of convex approximations by utilizing the Lagrangian duality, quadratic transformation, and alternating optimization. We then propose a robust joint covert beamforming algorithm (RJCB) to achieve near-optimal solutions for holographic and digital beamforming vectors. Finally, simulation results demonstrate that the proposed algorithm exhibits superior robustness and significantly enhanced covert communication capacity compared to benchmark schemes.