Cooperative Transmission Design for Secure Network assisted by Active RIS

Abstract This paper investigates a cooperative beamforming (BF) and jamming schemes in active reconfigurable intelligent surface (RIS)-assisted secure communication network, where an active RIS perform reflecting BF and a friendly jammer transmits jamming signal to enhance the security. Specifically, we consider a secrecy rate maximization problem under specific power constraints by assuming that perfect channel state information (CSI) of the eavesdroppers (Eves) can be obtained by the transmitter (Alice). Using the semidefinite relaxation (SDR) and CharnesCooper transformation, we address this problem by performing a one-dimensional search which involves solving a sequence of semidefinite programs (SDPs). For more practical scenario that perfect CSI of the Eves can not be obtained by Alice, a robust joint design of BF and jamming is proposed and the worst-case secrecy rate optimization is solved by using the S-procedure and its extension. Finally, simulation results demonstrate the performance gains of the proposed designs.