On the Spatial-Wideband Effects in Millimeter-Wave Cell-Free Massive MIMO

TL;DR

This paper studies the spatial-wideband effects in millimeter-wave cell-free massive MIMO systems, addressing synchronization, channel correlation, and interference issues to improve system performance in challenging mmWave environments.

Contribution

It introduces a minimum cyclic prefix length for OFDM synchronization and analyzes spatial correlations in the frequency-phase domain for CF-mMIMO.

Findings

Optimal cyclic prefix length reduces inter-symbol interference.

Spatial correlations impact system performance significantly.

CF-mMIMO enhances mmWave communication reliability.

Abstract

In this paper, we investigate the spatial-wideband effects in cell-free massive MIMO (CF-mMIMO) systems in mmWave bands. The utilization of mmWave frequencies brings challenges such as signal attenuation and the need for denser networks like ultra-dense networks (UDN) to maintain communication performance. CF-mMIMO is introduced as a solution, where distributed access points (APs) transmit signals to a central processing unit (CPU) for joint processing. CF-mMIMO offers advantages in reducing non-line-of-sight (NLOS) conditions and overcoming signal blockage. We investigate the synchronization problem in CF-mMIMO due to time delays between APs. It proposes a minimum cyclic prefix length to mitigate inter-symbol interference (ISI) in OFDM systems. Furthermore, the spatial correlations of channel responses are analyzed in the frequency-phase domain. The impact of these correlations on system performance is examined. The findings contribute to improving the performance of CF-mMIMO systems and enhancing the effective utilization of mmWave communication.