Abstract: Aiming at the security problems in the distributed satellite systems, two distributed secure beamforming algorithms based on eavesdropper location information are proposed to improve the secrecy performance. Considering the inaccurate location information of eavesdroppers, two optimization problems are formulated to maximize the achievable secrecy rate and minimize the transmit power, respectively. To solve these non-convex problems, the norm bound of channel state information is derived based on the eavesdropper location information, then, triangle inequality and Cauchy Schwartz inequality are adopted to deal with the channel error. After that, two distributed beamforming algorithms based on angle domain information are proposed to obtain the closed-form beamforming weight vectors with low computational complexity and fast convergence rate, providing theoretical basis for the deployment and application of distributed satellite communication system in the future. Finally, the effectiveness and superiority of the proposed scheme were confirmed through simulation results, where the secure communication can be achieved with lower complexity compared with traditional semidefinite programming algorithm, and the performance is improved by about 30% compared with the non-robust algorithm.

Key words: distributed satellite systems, physical layer security, distributed beamforming, location information, LEO（low earth orbit）satellite