Abstract
—In this paper, a multi-hop reconfigurable intelligent surfaces (RIS) aided multiple-input single-output (MISO) system is studied to mitigate significant channel attenuation in Millimeter wave and terahertz communication. The achievable sum rate of the system is maximized via optimizing the passive elements at the RISs with an iterative algorithm. Simulation results imply that the proposed algorithm is able to improve the achievable sum rate by increasing the number of RISs.