Impact of Channel Aging on Cell-Free Massive MIMO Over Spatially Correlated Channels

Zheng, Jiakang; Zhang, Jiayi; Björnson, Emil; Ai, Bo

doi:10.1109/twc.2021.3074421

Cited by 108 publications

(76 citation statements)

References 32 publications

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“…In addition, small cell systems are 6 We estimate the channel every time the train has travelled λ/5, which is frequent enough that the effect of channel aging can be ignored within each coherence block. Besides, Kalman filtering and/or machine learning can be used in the channel prediction for the channel aging reduction [28]. considered as a benchmark.…”

Section: B Results and Discussionmentioning

confidence: 99%

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Cell-Free Massive MIMO-OFDM for High-Speed Train Communications

Zheng¹,

Zhang²,

Björnson³

et al. 2022

Preprint

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Cell-free (CF) massive multiple-input multiple-output (MIMO) systems show great potentials in low-mobility scenarios, due to cell boundary disappearance and strong macro diversity. However, the great Doppler frequency offset (DFO) leads to serious inter-carrier interference in orthogonal frequency division multiplexing (OFDM) technology, which makes it difficult to provide high-quality transmissions for both high-speed train (HST) operation control systems and passengers. In this paper, we focus on the performance of CF massive MIMO-OFDM systems with both fully centralized and local minimum mean square error (MMSE) combining in HST communications. Considering the local maximum ratio (MR) combining, the large-scale fading decoding (LSFD) cooperation and the practical effect of DFO on system performance, exact closed-form expressions for uplink spectral efficiency (SE) expressions are derived. We observe that cooperative MMSE combining achieves better SE performance than uncooperative MR combining. In addition, HST communications with small cell and cellular massive MIMO-OFDM systems are compared in terms of SE. Numerical results reveal that the CF massive MIMO-OFDM system achieves a larger and more uniform SE than the other systems. Finally, the train antenna centric (TA-centric) CF massive MIMO-OFDM system is designed for practical implementation in HST communications, and three power control schemes are adopted to optimize the propagation of TAs for reducing the impact of the DFO.

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Section: B Results and Discussionmentioning

confidence: 99%

“…More importantly, the authors in [28] pointed out that, in both static and mobile scenarios, the CF massive MIMO system performs better than traditional cellular-based networks. In addition, the CF massive MIMO-OFDM system was presented and analyzed in [29], which provides a baseline for further studying.…”

Section: Introductionmentioning

confidence: 99%

Cell-Free Massive MIMO-OFDM for High-Speed Train Communications

Zheng¹,

Zhang²,

Björnson³

et al. 2022

Preprint

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“…The APs connected via fronthaul connections to a central processing unit (CPU), which is responsible for coordinating and processing the signals of all UEs. The user-centric CF architecture is adopted [19], where each UE accesses a subset of APs based on the channel condition. We let M k ⊂ {1, .…”

Section: System Setupmentioning

confidence: 99%

Treating Interference as Noise in Cell-Free Massive MIMO Networks

Chen¹,

Zhang²,

Chen³

et al. 2022

Preprint

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How to manage the interference introduced by the enormous wireless devices is a crucial issue to address in the prospective sixth-generation (6G) communications. The treating interference as noise (TIN) optimality conditions are commonly used for interference management and thus attract significant interest in existing wireless systems. Cell-free massive multipleinput multiple-output (CF mMIMO) is a promising technology in 6G that exhibits high system throughput and excellent interference management by exploiting a large number of access points (APs) to serve the users collaboratively. In this paper, we take the first step on studying TIN in CF mMIMO systems from a stochastic geometry perspective by investigating the probability that the TIN conditions hold with spatially distributed network nodes. We propose a novel analytical framework for TIN in a CF mMIMO system with both Binomial Point Process (BPP) and Poisson Point Process (PPP) approximations. We derive the probability that the TIN conditions hold in close form using the PPP approximation. Numerical results validate our derived expressions and illustrate the impact of various system parameters on the probability that the TIN conditions hold.

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“…, obtained by the terminal via downlink is used for reception. Unlike the scheme in the previous literature [8,[13][14][15], the channel hardening is no longer exploited, and channel statistical information,…”

Section: Cb With Instantaneous Csimentioning

confidence: 99%

“…Performance analysis approaches related to centralized massive MIMO are widely applied. Many works use statistical CSI for cell-free massive MIMO power control [8,[13][14][15]. The advantage of this approach is that large-scale fading tends to change slowly, so statistical information can reduce the amount of calculation.…”

Section: Introductionmentioning

confidence: 99%

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

Han

Zhao

2021

Entropy

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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.

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Impact of Channel Aging on Cell-Free Massive MIMO Over Spatially Correlated Channels

Cited by 108 publications

References 32 publications

Cell-Free Massive MIMO-OFDM for High-Speed Train Communications

Cell-Free Massive MIMO-OFDM for High-Speed Train Communications

Treating Interference as Noise in Cell-Free Massive MIMO Networks

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

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