Beam Focusing for Multi-User MIMO Communications with Dynamic Metasurface Antennas

Abstract

Recently, dynamic metasurface antennas (DMAs) have emerged as a promising technology for realizing massive multipleinput multiple-output (MIMO) wireless systems. The usage of large arrays, jointly with higher transmitted frequencies, often results in the communicating devices operating in the near-field (Fresnel) region, thus requiring different considerations compared to traditional systems, assumed to operate in the far-field regime. In this paper, we study the potential of beam focusing, feasible in near-field operation, for multiuser MIMO systems, where the base station is equipped with a DMA. We introduce a mathematical model for DMA-based near-field MIMO communications. Then, we characterize the sum-rate maximization problem of the considered system, and propose an efficient solution to jointly design the DMA weights and digital precoding vector. Simulation results show that our design generates focused beams such that users residing at the same angular direction can communicate reliably without interfering, which is not achievable using conventional far-field beam steering.Index terms-Beam focusing, dynamic metasurface antennas.

Holographic MIMO Communications: Theoretical Foundations, Enabling Technologies, and Future Directions

“…Employing a different optimization object, [238] studied the energy efficiency maximization problem in single-cell multi-user mMIMO systems, by jointly optimizing transmit precoding matrices of UEs and DMA weights of the BS, based on Dinkelbach's transform and AO method. This effort was later extended in [239] for further exploiting both instantaneous and statistical channel state information (CSI) in designing the joint transmit precoding With a particular focus on the beam focusing in nearfield scenario, a mathematical model for DMA-based nearfield multi-user MIMO systems was proposed in [240], incorporating both the feasible processing of DMAs as well as the propagation of the transmitted EM waves in near-field wireless communications. Then, the joint optimization of the DMA weights dictating its transmission pattern, and the digital precoding vector was considered, in order to maximize the sum-rate when operating in near-field, while accounting for the specific Lorentzian-form response of metamaterial elements.…”

Downlink Beamforming for Dynamic Metasurface Antennas

“…However, its use in cellular communication, particularly with massive MIMO, remains limited. A few studies have examined the use of DMAs in cellular communication and have served as a reference [6], [27]- [30]. For example, Shlezinger et al [27] studied the multi-user MIMO system, in which a base station (BS) uses DMA to receive signal streams sent from different user terminals.…”

Point focusing wireless communication: A diffraction limit communication paradigm

“…A beam focusing based on dynamic metasurface antennas was proposed for near-field MIMO communications. 21 This method needs to join to optimization of the dynamic metasurface antennas (DMAs) weights and digital precoders solve the non-convex problems. A dynamic focusing of large arrays based on orthogonal or pseudo-orthogonal masks was proposed for wireless power transfer (WPT).…”

“…Beam focusing can also improve the communication channel. A beam focusing based on dynamic meta‐surface antennas was proposed for near‐field MIMO communications 21 . This method needs to join to optimization of the dynamic metasurface antennas (DMAs) weights and digital precoders solve the non‐convex problems.…”