Measurement-Based Validation of Z3RO Precoder to Prevent Nonlinear Amplifier Distortion in Massive MIMO Systems

TL;DR

This paper validates the Z3RO precoder in real-world massive MIMO systems, demonstrating significant reduction in nonlinear amplifier distortion and improved signal quality at user locations through measurement-based analysis.

Contribution

It provides the first measurement-based validation of the Z3RO precoder's effectiveness in reducing nonlinear distortion in practical massive MIMO deployments.

Findings

Average distortion reduction of 6.03 dB in single-user scenarios

Distortion reduction of 3.54 dB in two-user scenarios

Effective suppression of out-of-band emissions

Abstract

In multiple input multiple output (MIMO) systems, precoding allows the base station to spatially focus and multiplex signals towards each user. However, distortion introduced by power amplifier nonlinearities coherently combines in the same spatial directions when using a conventional precoder such as maximum ratio transmission (MRT). This can strongly limit the user performance and moreover create unauthorized out-of-band (OOB) emissions. In order to overcome this problem, the zero third-order distortion (Z3RO) precoder was recently introduced. This precoder constraints the third-order distortion at the user location to be zero. In this work, the performance of the Z3RO precoder is validated based on real-world channel measurement data. The results illustrate the reduction in distortion power at the UE locations: an average distortion reduction of 6.03 dB in the worst-case single-user scenario and 3.54 dB in the 2-user case at a back-off rate of -3 dB.