The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels

In centralized massive multiple-input multiple-output (MIMO) systems, the channel hardening phenomenon can occur, in which the channel behaves as almost fully deterministic as the number of antennas increases. Nevertheless, in a cell-free massive MIMO system, the channel is less deterministic. In th...

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Autores principales:	Tongzhou Han, Danfeng Zhao
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	cell-free massive MIMO FDD conjugate beamforming downlink transmission power control Science Q Astrophysics QB460-466 Physics QC1-999
Acceso en línea:	https://doaj.org/article/90e6c1f9a61d445fb50f8098e95e4d7c
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id	oai:doaj.org-article:90e6c1f9a61d445fb50f8098e95e4d7c
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spelling	oai:doaj.org-article:90e6c1f9a61d445fb50f8098e95e4d7c2021-11-25T17:30:56ZThe Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels10.3390/e231115521099-4300https://doaj.org/article/90e6c1f9a61d445fb50f8098e95e4d7c2021-11-01T00:00:00Zhttps://www.mdpi.com/1099-4300/23/11/1552https://doaj.org/toc/1099-4300In centralized massive multiple-input multiple-output (MIMO) systems, the channel hardening phenomenon can occur, in which the channel behaves as almost fully deterministic as the number of antennas increases. Nevertheless, in a cell-free massive MIMO system, the channel is less deterministic. In this paper, we propose using instantaneous channel state information (CSI) instead of statistical CSI to obtain the power control coefficient in cell-free massive MIMO. Access points (APs) and user equipment (UE) have sufficient time to obtain instantaneous CSI in a slowly time-varying channel environment. We derive the achievable downlink rate under instantaneous CSI for frequency division duplex (FDD) cell-free massive MIMO systems and apply the results to the power control coefficients. For FDD systems, quantized channel coefficients are proposed to reduce feedback overhead. The simulation results show that the spectral efficiency performance when using instantaneous CSI is approximately three times higher than that achieved using statistical CSI.Tongzhou HanDanfeng ZhaoMDPI AGarticlecell-free massive MIMOFDDconjugate beamformingdownlink transmissionpower controlScienceQAstrophysicsQB460-466PhysicsQC1-999ENEntropy, Vol 23, Iss 1552, p 1552 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	cell-free massive MIMO FDD conjugate beamforming downlink transmission power control Science Q Astrophysics QB460-466 Physics QC1-999
spellingShingle	cell-free massive MIMO FDD conjugate beamforming downlink transmission power control Science Q Astrophysics QB460-466 Physics QC1-999 Tongzhou Han Danfeng Zhao The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels
description	In centralized massive multiple-input multiple-output (MIMO) systems, the channel hardening phenomenon can occur, in which the channel behaves as almost fully deterministic as the number of antennas increases. Nevertheless, in a cell-free massive MIMO system, the channel is less deterministic. In this paper, we propose using instantaneous channel state information (CSI) instead of statistical CSI to obtain the power control coefficient in cell-free massive MIMO. Access points (APs) and user equipment (UE) have sufficient time to obtain instantaneous CSI in a slowly time-varying channel environment. We derive the achievable downlink rate under instantaneous CSI for frequency division duplex (FDD) cell-free massive MIMO systems and apply the results to the power control coefficients. For FDD systems, quantized channel coefficients are proposed to reduce feedback overhead. The simulation results show that the spectral efficiency performance when using instantaneous CSI is approximately three times higher than that achieved using statistical CSI.
format	article
author	Tongzhou Han Danfeng Zhao
author_facet	Tongzhou Han Danfeng Zhao
author_sort	Tongzhou Han
title	The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels
title_short	The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels
title_full	The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels
title_fullStr	The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels
title_full_unstemmed	The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels
title_sort	downlink performance for cell-free massive mimo with instantaneous csi in slowly time-varying channels
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/90e6c1f9a61d445fb50f8098e95e4d7c
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The Downlink Performance for Cell-Free Massive MIMO with Instantaneous CSI in Slowly Time-Varying Channels

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