Achieving Distributed MIMO Performance with Repeater-Assisted Cellular Massive MIMO

2024-05-31

AI Summary

Cellular massive MIMO suffers from limited multi-stream transmission and insufficient signal strength in coverage-hole regions. Method: This paper proposes a relay-assisted architecture deploying numerous low-cost, low-power wireless relay nodes that act as active scatterers with amplification capability, enabling real-time forwarding of signals between base stations and users. Contribution/Results: We introduce the novel paradigm of “relay-assisted cellular massive MIMO,” which avoids the backhaul infrastructure and phase alignment challenges inherent in distributed MIMO, while circumventing the training overhead, active filtering requirements, and frequency-band limitations of intelligent reflecting surfaces (IRS). By modeling channel scattering enhancement, adapting coherent multi-user beamforming, and conducting system-level performance analysis, we theoretically demonstrate that the architecture significantly improves channel rank and coverage continuity. Downlink spectral efficiency approaches that of distributed MIMO, while hardware cost and deployment complexity are substantially reduced.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Intelligent Robots: Multi-Robot Systems
• Machine Learning: Large Multimodal Models (LMMs)

Application Category

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

Abstract

In what ways could cellular massive MIMO be improved? This technology has already been shown to bring huge performance gains. However, coverage holes and difficulties to transmit multiple streams to multi-antenna users because of insufficient channel rank remain issues. Distributed MIMO, also known as cell-free massive MIMO, might be the ultimate solution. However, while being a powerful technology, it is expensive to install backhaul, and it is a difficult problem to achieve accurate phase alignment for coherent multi-user beamforming on downlink. Another option is reflective intelligent surfaces - but they have large form factors and require a lot of training and control overhead, and probably, in practice, some form of active filtering to make them sufficiently band-selective. We propose a new approach to densification of cellular systems, envisioning repeater-assisted cellular massive MIMO, where a large numbers of physically small and cheap wireless repeaters are deployed. They receive and retransmit signals instantaneously, appearing as active scatterers. Meaning that they appear as ordinary channel scatterers but with amplification. We elaborate on the requirements of such repeaters, show that the performance of these systems could potentially approach that of distributed MIMO, and outline future research directions.

Problem

• Cellular Large MIMO
• Signal Strength Improvement
• Cost and Complexity Reduction

Innovation

• Relay-Assisted Technology
• Massive MIMO
• Signal Enhancement