Optimization of Decode-and-Forward Relaying and RIS Aided MISO System

This paper proposes a decode-and-forward (DF) and reconfigurable intelligent surface (RIS) aided multiple-input single-output (MISO) (DF-RIS MISO) system to avoid the “double fading” effect introduced by RIS. The closed-form average bit error rate (ABER) of the DF-RIS MISO system is derived and the joint optimization of the active and passive beamforming and power allocation is presented to maximize the system achievable rate. Numerical simulations verify that the proposed DF-RIS MISO system enables RIS and DF to work complementary and avoid the “double fading” effect significantly. Meanwhile, the proposed system with joint beamforming and power allocation optimization achieves better achievable rate and ABER performance compared with the typical systems. Furthermore, we have discussed the best relay location in this paper as well.