The Tri-Hybrid MIMO Architecture

TL;DR

The paper introduces the tri-hybrid MIMO architecture, combining digital, analog, and reconfigurable antennas to enhance scalability and efficiency for future 6G wireless systems.

Contribution

It presents a novel three-layer MIMO framework integrating reconfigurable antennas, expanding beyond traditional hybrid MIMO architectures.

Findings

Reconfigurable antennas enable new tradeoffs in spectral and energy efficiency.

The tri-hybrid architecture offers scalable MIMO solutions for 6G systems.

Challenges in configuration across the three layers are identified and discussed.

Abstract

We present an evolution of multiple-input multiple-output (MIMO) wireless communications known as the tri-hybrid MIMO architecture. In this framework, the traditional operations of linear precoding at the transmitter are distributed across digital beamforming, analog beamforming, and reconfigurable antennas. Compared with the hybrid MIMO architecture, which combines digital and analog beamforming, the tri-hybrid approach introduces a third layer of electromagnetic beamforming through antenna reconfigurability. This added layer offers a pathway to scale MIMO spatial dimensions, important for 6G systems operating in centimeter-wave bands, where the tension between larger bandwidths and infrastructure reuse necessitates ultra-large antenna arrays. We introduce the key features of the tri-hybrid architecture by (i)~reviewing the benefits and challenges of communicating with reconfigurable antennas, (ii)~examining tradeoffs between spectral and energy efficiency enabled by reconfigurability, and (iii)~exploring configuration challenges across the three layers. Overall, the tri-hybrid MIMO architecture offers a new approach for integrating emerging antenna technologies in the MIMO precoding framework.