This paper focuses on studying orthogonal and non-orthogonal multiple access in intelligent reflecting surface (IRS)-aided systems. Unlike most prior works assuming continuous phase shifts, we employ the practical setup where only a finite number of discrete phase shifts are available. To maximize the sum rate, active beamforming and discrete reflection need to be jointly optimized. We therefore propose an alternative optimization method to get the optimal continuous phase shifts iteratively, and then quantize each phase shift to its nearest discrete value. The sum-rate maximization of different schemes is theoretically analyzed and numerically evaluated with different numbers of phase-control bits.

翻译：本文聚焦于研究智能反射表面（IRS）辅助系统中正交与非正交多址接入。与多数现有工作假设连续相位偏转不同，我们采用仅有限数量离散相位偏转可用的实际设置。为最大化总速率，需联合优化主动波束赋形与离散反射。据此提出一种交替优化方法，通过迭代获得最优连续相位偏转，再对每个相位偏转量化至其最近离散值。理论分析并数值评估了不同相位控制比特数下各方案的总速率最大化性能。