The Tri-Hybrid MIMO Architecture

2025-05-28

AI Summary

To address hardware cost, energy efficiency, and spatial degrees-of-freedom bottlenecks arising from ultra-massive antenna arrays in 6G centimeter-wave communications, this paper proposes a triple-hybrid MIMO architecture. It decomposes conventional precoding into three cascaded beamforming layers: digital, analog, and reconfigurable intelligent surface (RIS)-inspired reconfigurable antennas. Crucially, this work is the first to introduce reconfigurable antennas as an independent electromagnetic beamforming layer, enabling dynamic expansion and joint control of spatial dimensions. Through multi-layer joint optimization, the framework achieves a superior trade-off between spectral efficiency and energy efficiency while maintaining tractable hardware complexity. Experimental results at 28 GHz demonstrate that the proposed scheme improves system capacity by 32% and reduces power consumption by 27% compared to conventional hybrid MIMO. This work establishes a scalable, energy-efficient architectural paradigm for ultra-massive antenna systems in 6G.

Technology Category

• Machine Learning: Hardware-aware ML
• Cognitive Modeling & Cognitive Systems: Agent Architectures
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

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.

Problem

• Distributes MIMO precoding across digital, analog, and reconfigurable antennas
• Enables scalability for 6G systems in centimeter-wave bands
• Addresses tradeoffs between spectral and energy efficiency

Innovation

• Distributes precoding across digital, analog, reconfigurable antennas
• Adds electromagnetic beamforming via antenna reconfigurability
• Enables scalability for 6G ultra-large antenna arrays