Joint Beamforming Designs for Active Reconfigurable Intelligent Surface: A Sub-Connected Array Architecture

Reconfigurable intelligent surface (RIS) is regarded as a promising technology with great potential to boost wireless networks. Affected by the “double fading” effect, however, conventional passive RIS cannot bring considerable performance improvement when users are not close enough RIS. Recently, active introduced combat double fading effect actively amplifying incident signals aid of integrated reflection-type amplifiers. In order reduce hardware cost and energy consumption due massive components in fully-connected RIS, novel hardware-and-energy efficient sub-connected architecture has been proposed recently, which multiple reconfigurable electromagnetic elements driven only one amplifier. this paper, we first develop an improved accurate signal model for architecture. Then, investigate joint transmit precoding reflection beamforming (i.e., phase-shift amplification coefficients) designs multiuser multiple-input single-output (MU-MISO) communication systems. Both sum-rate maximization power minimization problems solved leveraging fractional programming (FP), block coordinate descent (BCD), second-order cone (SOCP), alternating direction method multipliers (ADMM), majorization-minimization (MM) methods. Extensive simulation results verify that compared structure, can significantly consumption, achieve budget at limited.