  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.
