Network-Controlled Repeaters Under Power Amplifier Non-linearities

2026-04-15

AI Summary

This work addresses the performance degradation caused by nonlinear distortion from power amplifiers in relay-assisted massive MIMO uplink systems, where such distortion impairs multiuser signal separation. To tackle this challenge, the paper proposes a distortion-aware receiver design framework that explicitly incorporates the statistical characteristics of nonlinear distortion into system modeling—despite the absence of channel state information at the relay. Leveraging a memoryless third-order polynomial power amplifier model and Bussgang decomposition, closed-form expressions for both the Bussgang gain matrix and the distortion covariance are derived. Building upon these results and employing tools from random matrix theory, an optimal linear combining vector is designed to maximize the effective signal-to-interference-plus-distortion ratio. This approach enables accurate modeling and effective suppression of nonlinear distortion, yielding substantial improvements in system spectral efficiency.

Technology Category

• Search and Optimization: Non-convex Optimization
• Intelligent Robots: State Estimation
• Machine Learning: Mixture of Experts (MoE)

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Security and Privacy: Large-scale security measurements

Abstract

Network-controlled repeaters (NCRs) are a low-cost means to extend coverage and strengthen macro diversity in wireless networks. They operate in real time by amplifying and re-transmitting the incoming signal with only hardware-level delays, without requiring any channel state information (CSI) at the repeater itself. However, their power amplifiers (PAs) generate non-linear distortion that is jointly forwarded with the desired signal and can undermine multiuser performance unless the distortion statistics are exploited. This paper develops a distortion-aware (DA) uplink framework for repeater-assisted massive MIMO (RA-MIMO) under PA non-linearities. We adopt a memoryless third-order polynomial model for the repeater PA and characterize the achievable spectral efficiency (SE) using the Bussgang decomposition. Closed-form expressions are derived for the Bussgang gain matrix and the distortion covariance. We also design a DA combining vector that maximizes the effective signal-to-interference-plus-distortion ratio.

Problem

• Network-controlled repeaters
• Power amplifier non-linearities
• Massive MIMO
• Distortion-aware
• Spectral efficiency

Innovation

• distortion-aware
• power amplifier non-linearities
• massive MIMO
• Bussgang decomposition
• network-controlled repeaters