Abstract:In order to enhance the security of multi-beam satellite communication system with multiple eavesdroppers, under the condition of available statistical channel state information, two beamforming (BF) schemes respectively for minimizing the total transmit power and maximizing the secrecy rate were proposed. Firstly, an optimization problem was formulated to minimize the satellite total transmit power while satisfying the secrecy rate requirement, and the analytical expression of optimal BF weight vector was obtained by adopting the Lagrange multiplier method. Then, two optimization problems were established to maximize secrecy rate with the constraint of total transmit power and per-antenna power budget, respectively. For the total transmit power constraint, the analytic expression of optimal BF weight vector was obtained by using generalized Rayleigh quotient method. For the per-antenna power constraint, the non-convex problem was converted into a convex one by introducing auxiliary variable, and further an iterative golden section-based algorithm was proposed to obtain the optimal BF weight vectors. Finally, the simulation results confirmed the effectiveness and validity of the proposed BF schemes. Meanwhile, the effect of the system parameters on the security performance was also analyzed. Compared to the traditional BF schemes, the proposed three BF schemes can obtain better secrecy performance.