Subspace-Based Pilot Decontamination in User-Centric Scalable Cell-Free Wireless Networks Article Swipe

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Fabian Göttsch , Noboru Osawa , Takeo Ohseki , Kosuke Yamazaki , Giuseppe Caire ·

YOU? · · 2022 · Open Access · · DOI: https://doi.org/10.48550/arxiv.2203.00714

We consider a cell-free wireless system operated in Time Division Duplex (TDD) mode with user-centric clusters of remote radio units (RUs). Since the uplink pilot dimensions per channel coherence slot is limited, co-pilot users might incur mutual pilot contamination. In the current literature, it is assumed that the long-term statistical knowledge of all user channels is available. This enables Minimum Mean-Square Error channel estimation or simplified dominant subspace projection, which achieves significant pilot decontamination under certain assumptions on the channel covariance matrices. However, estimating the channel covariance matrix or even just its dominant subspace at all RUs forming a user cluster is not an easy task. In fact, if not properly designed, a piloting scheme for such long-term statistics estimation will also be subject to the contamination problem. In this paper, we propose a new channel subspace estimation scheme explicitly designed for cell-free wireless networks. Our scheme is based on 1) a sounding reference signal (SRS) using latin squares wideband frequency hopping, and 2) a subspace estimation method based on robust Principal Component Analysis (R-PCA). The SRS hopping scheme ensures that for any user and any RU participating in its cluster, only a few pilot measurements will contain strong co-pilot interference. These few heavily contaminated measurements are (implicitly) eliminated by R-PCA, which is designed to regularize the estimation and discount the ``outlier'' measurements. Our simulation results show that the proposed scheme achieves almost perfect subspace knowledge, which in turns yields system performance very close to that with ideal channel state information, thus essentially solving the problem of pilot contamination in cell-free user-centric TDD wireless networks.

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Artificial Intelligence

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Subspace topology Computer science Telecommunications link Signal subspace Covariance matrix Channel (broadcasting) Outlier Algorithm Covariance Channel state information Wireless Real-time computing Statistics Computer network Mathematics Telecommunications Noise (video) Artificial intelligence Image (mathematics)

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Type: preprint
Language: en
Landing Page: http://arxiv.org/abs/2203.00714
PDF: https://arxiv.org/pdf/2203.00714
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Cited By: 4
Related Works: 10
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DOI: https://doi.org/10.48550/arxiv.2203.00714

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Title: Subspace-Based Pilot Decontamination in User-Centric Scalable Cell-Free Wireless Networks

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Language: en

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Publication year: 2022

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Publication date: 2022-03-01

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Authors: Fabian Göttsch, Noboru Osawa, Takeo Ohseki, Kosuke Yamazaki, Giuseppe Caire

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Landing page: https://arxiv.org/abs/2203.00714

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Concepts: Subspace topology, Computer science, Telecommunications link, Signal subspace, Covariance matrix, Channel (broadcasting), Outlier, Algorithm, Covariance, Channel state information, Wireless, Real-time computing, Statistics, Computer network, Mathematics, Telecommunications, Noise (video), Artificial intelligence, Image (mathematics)

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Cited by: 4

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Citations by year (recent): 2025: 1, 2023: 2, 2022: 1

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abstract_inverted_index.current	41
abstract_inverted_index.enables	58
abstract_inverted_index.ensures	179
abstract_inverted_index.forming	97
abstract_inverted_index.heavily	203
abstract_inverted_index.hopping	177
abstract_inverted_index.perfect	233
abstract_inverted_index.problem	255
abstract_inverted_index.propose	132
abstract_inverted_index.results	225
abstract_inverted_index.solving	253
abstract_inverted_index.squares	158
abstract_inverted_index.subject	123
abstract_inverted_index.(R-PCA).	174
abstract_inverted_index.Analysis	173
abstract_inverted_index.Division	9
abstract_inverted_index.However,	82
abstract_inverted_index.achieves	70, 231
abstract_inverted_index.channels	54
abstract_inverted_index.cluster,	190
abstract_inverted_index.clusters	15
abstract_inverted_index.co-pilot	32, 199
abstract_inverted_index.consider	1
abstract_inverted_index.designed	140, 213
abstract_inverted_index.discount	219
abstract_inverted_index.dominant	66, 92
abstract_inverted_index.hopping,	161
abstract_inverted_index.limited,	31
abstract_inverted_index.operated	6
abstract_inverted_index.piloting	113
abstract_inverted_index.problem.	127
abstract_inverted_index.properly	110
abstract_inverted_index.proposed	229
abstract_inverted_index.sounding	152
abstract_inverted_index.subspace	67, 93, 136, 165, 234
abstract_inverted_index.wideband	159
abstract_inverted_index.wireless	4, 143, 263
abstract_inverted_index.Component	172
abstract_inverted_index.Principal	171
abstract_inverted_index.cell-free	3, 142, 260
abstract_inverted_index.coherence	28
abstract_inverted_index.designed,	111
abstract_inverted_index.frequency	160
abstract_inverted_index.knowledge	50
abstract_inverted_index.long-term	48, 117
abstract_inverted_index.matrices.	81
abstract_inverted_index.networks.	144, 264
abstract_inverted_index.reference	153
abstract_inverted_index.available.	56
abstract_inverted_index.covariance	80, 86
abstract_inverted_index.dimensions	25
abstract_inverted_index.eliminated	208
abstract_inverted_index.estimating	83
abstract_inverted_index.estimation	63, 119, 137, 166, 217
abstract_inverted_index.explicitly	139
abstract_inverted_index.knowledge,	235
abstract_inverted_index.regularize	215
abstract_inverted_index.simplified	65
abstract_inverted_index.simulation	224
abstract_inverted_index.statistics	118
abstract_inverted_index.Mean-Square	60
abstract_inverted_index.``outlier''	221
abstract_inverted_index.assumptions	76
abstract_inverted_index.essentially	252
abstract_inverted_index.literature,	42
abstract_inverted_index.performance	241
abstract_inverted_index.projection,	68
abstract_inverted_index.significant	71
abstract_inverted_index.statistical	49
abstract_inverted_index.(implicitly)	207
abstract_inverted_index.contaminated	204
abstract_inverted_index.information,	250
abstract_inverted_index.measurements	195, 205
abstract_inverted_index.user-centric	14, 261
abstract_inverted_index.contamination	126, 258
abstract_inverted_index.interference.	200
abstract_inverted_index.measurements.	222
abstract_inverted_index.participating	187
abstract_inverted_index.contamination.	38
abstract_inverted_index.decontamination	73
cited_by_percentile_year
countries_distinct_count	0
institutions_distinct_count	5
citation_normalized_percentile