Beamforming Vector Optimization Algorithm in RIS-Based Non-Terrestrial Systems

The high frequency in the THz band is attracting attention as a key element of the 6G system because of its wide bandwidth and high transmission rate, but technology is needed to compensate for this due to the large path loss. Therefore, we introduce an algorithm to improve security performance by using non-terrestrial network (NTN) and reconfigurable intelligent surface (RIS). The proposed algorithm is largely composed of two parts. It is divided into the part that optimizes the base station beamforming vector using the successive convex approximation (SCA) algorithm and the part that optimizes the RIS beamforming vector using the minorization-maximization (MM) algorithm. As a result of performance analysis through simulation, the superiority of the proposed algorithm was confirmed in terms of system security performance.