liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Performance of Cell-Free Massive MIMO With Rician Fading and Phase Shifts
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-5954-434X
Beijing Jiaotong Univ, Peoples R China.
2019 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 18, no 11, p. 5299-5315Article in journal (Refereed) Published
Abstract [en]

In this paper, we study the uplink (UL) and downlink (DL) spectral efficiency (SE) of a cell-free massive multiple-input-multiple-output (MIMO) system over Rician fading channels. The phase of the line-of-sight (LoS) path is modeled as a uniformly distributed random variable to take the phase-shifts due to mobility and phase noise into account. Considering the availability of prior information at the access points (APs), the phase-aware minimum mean square error (MMSE), non-aware linear MMSE (LMMSE), and least-square (LS) estimators are derived. The MMSE estimator requires perfectly estimated phase knowledge whereas the LMMSE and LS are derived without it. In the UL, a two-layer decoding method is investigated in order to mitigate both coherent and non-coherent interference. Closed-form UL SE expressions with phase-aware MMSE, LMMSE, and LS estimators are derived for maximum-ratio (MR) combining in the first layer and optimal large-scale fading decoding (LSFD) in the second layer. In the DL, two different transmission modes are studied: coherent and non-coherent. Closed-form DL SE expressions for both transmission modes with MR precoding are derived for the three estimators. Numerical results show that the LSFD improves the UL SE performance and coherent transmission mode performs much better than non-coherent transmission in the DL. Besides, the performance loss due to the lack of phase information depends on the pilot length and it is small when the pilot contamination is low.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC , 2019. Vol. 18, no 11, p. 5299-5315
Keywords [en]
Channel estimation; Fading channels; Rician channels; Coherence; Random variables; Decoding; Cell-free massive MIMO; Rician fading; phase shift; performance analysis
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:liu:diva-162767DOI: 10.1109/TWC.2019.2935434ISI: 000496947800020OAI: oai:DiVA.org:liu-162767DiVA, id: diva2:1379782
Note

Funding Agencies|ELLIIT; Swedish Research CouncilSwedish Research Council; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [61601020, U1834210]; Beijing Natural Science FoundationBeijing Natural Science Foundation [4182049, L171005]

Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2020-02-18
In thesis
1. Analysis of Cellular and Cell-Free Massive MIMO with Rician Fading
Open this publication in new window or tab >>Analysis of Cellular and Cell-Free Massive MIMO with Rician Fading
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The data traffic in cellular networks has grown at an exponential pace for decades. This trend will most probably continue in the future, driven by new innovative applications. One of the key enablers of future cellular networks is the massive MIMO technology. A massive MIMO base station is equipped with a massive number (e.g., a hundred) of individually steerable antennas, which can be effectively used to serve tens of user equipments simultaneously on the same time-frequency resource. It can provide a notable enhancement of both spectral efficiency and energy efficiency in comparison with conventional MIMO.

In the literature, the achievable spectral efficiencies of massive MIMO systems with a practical number of antennas have been rigorously characterized and optimized when the channels are subject to either spatially uncorrelated or correlated Rayleigh fading. Typically, in massive MIMO research, i.i.d. Rayleigh fading or less frequently free-space line-of-sight (LoS) channel models are assumed since they simplify the analysis. Massive MIMO technology is able to support both rich scattering and LoS scenarios. However, practical channels can consist of a combination of an LoS path and a correlated small-scale fading component caused by a finite number of scattering clusters that can be modeled by spatially correlated Rician fading. In the first part of this thesis, we consider a multi-cell scenario with spatially correlated Rician fading channels and derive closed-form achievable spectral efficiency expressions for different signal processing techniques.

Alternatively, a massive number of antennas can be spread over a large geographical area and this concept is called cell-free massive MIMO. In the canonical form of cell-free massive MIMO, the access points cooperate via a fronthaul network to spatially multiplex the users on the same time-frequency resource using network MIMO methods that only require locally obtained channel state information. Cellfree massive MIMO is a densely deployed system. Hence, the probability of having an LoS path between some access points and the users is quite high. In the second part of this thesis, we consider a practical scenario where the channels between the access points and the users are modeled with Rician fading.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2020. p. 34
Series
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1870
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-163688 (URN)10.3384/lic.diva-163688 (DOI)9789179299118 (ISBN)
Presentation
2020-03-02, Transformen, B-house, entrance 27, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2020-02-18 Created: 2020-02-18 Last updated: 2020-02-18Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Search in DiVA

By author/editor
Özdogan, ÖzgecanBjörnson, Emil
By organisation
Communication SystemsFaculty of Science & Engineering
In the same journal
IEEE Transactions on Wireless Communications
Telecommunications

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 21 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf