This paper aims to explore reconfigurable intelligent surface (RIS) integration in a millimeter wave (mmWave) communication system with low-complexity transceiver architecture under imperfect CSI assumption. Towards this, we propose a RIS-aided system with a fully analog (FA) architecture at the base station. However, to overcome the disadvantage of single-user transmission due to the single RF-chain, we employ NOMA. For such a system, we formulate sum rate (SR) and energy efficiency (EE) maximization problems to obtain the joint transmit beamformer, RIS phase shift matrix, and power allocation solutions under minimum rate constraint. We first tackle the fractional objectives of both problems by reformulating the SR and EE maximization problems into equivalent quadratic forms using the quadratic transform. On the other hand, we employ successive convex approximation and the semi-definite relaxation technique to handle the non-convex minimum rate and unit modulus constraint of the RIS phase shifts, respectively. Next, we propose an alternating optimization-based algorithm that iterates over the transmit beamformer, power allocation, and RIS phase shift subproblems. Further, we also show that the quadratic reformulation is equivalent to the WMSE-based reformulation for the case of SR maximization problem. Our numerical results show that the proposed RIS-NOMA integrated FA architecture system outperforms the optimally configured fully digital architecture in terms of SR at low SNR and EE for a wide range of SNR while still maintaining low hardware complexity and cost. Finally, we present the numerical performance analysis of the RIS-NOMA integrated low-complexity system for various system configuration parameters.

翻译：本文旨在探索在不完美信道状态信息假设下，将可重构智能表面（RIS）集成至具有低复杂度收发架构的毫米波（mmWave）通信系统。为此，我们提出了一种基站采用全模拟（FA）架构的RIS辅助系统。然而，为克服单射频链路导致的单用户传输缺陷，我们引入了非正交多址接入（NOMA）。针对该系统，我们构建了总速率（SR）与能量效率（EE）最大化问题，以在最小速率约束下联合求解发射波束成形器、RIS相位偏移矩阵及功率分配方案。首先，通过二次变换将SR与EE最大化问题的分数目标函数重构为等效二次形式；其次，分别采用逐次凸近似与半定松弛技术处理非凸的最小速率约束及RIS相位偏移的单位模约束。随后，我们提出了一种基于交替优化的算法，迭代求解发射波束成形器、功率分配及RIS相位偏移子问题。此外，我们还证明了对于SR最大化问题，二次重构与基于加权最小均方误差（WMSE）的重构具有等价性。数值结果表明，所提出的RIS-NOMA集成全模拟架构系统在低信噪比（SNR）下的总速率以及宽泛SNR范围内的能量效率均优于最优配置的全数字架构，同时保持了较低的硬件复杂度与成本。最后，我们针对不同系统配置参数，对RIS-NOMA集成低复杂度系统进行了数值性能分析。