Joint Active and Passive Beamforming for IRS-Aided Multiuser Systems with Low-Resolution DACs

We investigate the problem of joint active and passive beamforming for intelligent reflecting surface (IRS)-aided multi-user multiple-input multiple-output (MIMO) communication systems where the base station (BS) adopts low-resolution DACs to reduce the power consumption and hardware complexity. The additive quantization noise model (AQNM) is employed to model the nonlinear quantization operation. Given a pre-specified minimum achievable rate for each user, an optimization which aims to minimize the transmit power is formulated. We devise an iterative algorithm based on alternating optimization and semi-definite relaxation (SDR) techniques. Numerical results verify the effectiveness of the proposed method.