Joint Reflecting and Precoding Designs for SER Minimization in Reconfigurable Intelligent Surfaces Assisted MIMO Systems

Abstract

This paper investigates the use of a reconfigurable intelligent surface (RIS) to aid point-to-point multi-data-stream multiple-input multiple-output (MIMO) wireless communications. With practical finite alphabet input, the reflecting elements at the RIS and the precoder at the transmitter are alternatively optimized to minimize the symbol error rate (MSER). In the reflecting optimization with a fixed precoder, two reflecting design methods are developed, referred as eMSER-Reflecting and vMSER-Reflecting. In the optimization of the precoding matrix with a fixed reflecting pattern, the matrix optimization is transformed to be a vector optimization problem and two methods are proposed to solve it, which are referred as MSER-Precoding and MMED-Precoding. The superiority of the proposed designs is investigated by simulations. Simulation results demonstrate that the proposed reflecting and precoding designs can offer a lower SER than existing designs with the assumption of complex Gaussian input.Moreover, we compare RIS with a full-duplex Amplify-and-Forward (AF) relay system in terms of SER to show the advantage of RIS.

Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How It Works, State of Research, and The Road Ahead

“…In [179], the authors consider the joint design of the RIS phase shifts and the full rank precoder at the transmitter in a point-to-point RIS-assisted MIMO system. The problem of minimizing the error probability is tackled by employing the alternating maximization method, wherein the two subproblems are globally solved.…”

Large Intelligent Surfaces With Discrete Set of Phase-Shifts Communicating Through Double-Rayleigh Fading Channels

“…A. Approximated PDF of the Instantaneous SNR Let the random variable Z = r, where r is defined in (6), therefore, the PDF of Z can be accurately approximated by a Gamma distribution with parameters κ and θ, defined by (7) and (8), respectively. This is empirically proven by comparing the normalized histogram of Z against the theoretical PDF of a Gamma random variable, Y , with the parameters defined earlier.…”

“…Although some studies optimize the reflection coefficients (amplitude and phase) of each LIS element [6], the reflection phases' high precision configuration is unfeasible since the number of bits is limited. As a consequence, phase quantization errors arise.…”

Large Intelligent Surfaces With Discrete Set of Phase-Shifts Communicating Through Double-Rayleigh Fading Channels

“…|g n ||h n |e jδn , (6) and the theoretical PDF of a Gamma random variable, it is possible to say that the PDF of r can be accurately approximated by the Gamma PDF with shape and scale parameters given by κ and θ, respectively as…”