LSFD for Rician-Faded Cell-Free mMIMO Systems With Channel Aging and Hardware Impairments

TL;DR

This paper analyzes the effects of channel aging and hardware impairments on cell-free mMIMO systems with Rician fading, proposing spectral efficiency expressions and demonstrating LSFD's mitigation capabilities.

Contribution

It derives a closed-form spectral efficiency expression considering practical impairments and channel aging, and evaluates LSFD's effectiveness in mitigating these issues.

Findings

LSFD mitigates channel aging effects for various UE velocities.

Hardware impairments significantly impact spectral efficiency.

Channel aging reduces system performance, but LSFD offers effective mitigation.

Abstract

We study the impact of channel aging on the uplink of a cell-free massive multiple-input multiple-output system with hardware impairments. We consider a dynamic analog-to-digital converter architecture at the access points (APs), and low-resolution digital-to-analog converters at the user equipments (UEs). We derive a closed-form spectral efficiency expression by considering i) practical spatially-correlated Rician channels; ii) hardware impairments at the APs and the UEs; iii) channel aging; and iv) large-scale fading decoding (LSFD). We show that LSFD can effectively mitigate the detrimental effects of i) channel aging for both low and high UE velocities; and ii) inter-user interference for low-velocity UEs but not for high-velocity UEs.