Hybrid RIS and DMA Assisted Multiuser MIMO Uplink Transmission With Electromagnetic Exposure Constraints

TL;DR

This paper proposes a novel spectral efficiency maximization scheme for multiuser MIMO uplink systems assisted by hybrid RIS and DMA, incorporating electromagnetic exposure constraints to ensure public health safety.

Contribution

It introduces an alternating optimization framework for joint design of transmit covariance, RIS phase shifts, and DMA weights under EM constraints, with closed-form solutions and iterative algorithms.

Findings

The proposed scheme outperforms conventional baselines in spectral efficiency.

The EM-aware design effectively reduces electromagnetic radiation exposure.

Numerical results validate the convergence and effectiveness of the optimization approach.

Abstract

In the fifth-generation and beyond era, reconfigurable intelligent surface (RIS) and dynamic metasurface antennas (DMAs) are emerging metamaterials keeping up with the demand for high-quality wireless communication services, which promote the diversification of portable wireless terminals. However, along with the rapid expansion of wireless devices, the electromagnetic (EM) radiation increases unceasingly and inevitably affects public health, which requires a limited exposure level in the transmission design. To reduce the EM radiation and preserve the quality of communication service, we investigate the spectral efficiency (SE) maximization with EM constraints for uplink transmission in hybrid RIS and DMA assisted multiuser multiple-input multiple-output systems. Specifically, alternating optimization is adopted to optimize the transmit covariance, RIS phase shift, and DMA weight matrices. We first figure out the water-filling solutions of transmit covariance matrices with given RIS and DMA parameters. Then, the RIS phase shift matrix is optimized via the weighted minimum mean square error, block coordinate descent and minorization-maximization methods. Furthermore, we solve the unconstrainted DMA weight matrix optimization problem in closed form and then design the DMA weight matrix to approach this performance under DMA constraints. Numerical results confirm the effectiveness of the EM aware SE maximization transmission scheme over the conventional baselines.