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Electronics
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MIMO System Technology for Wireless Communications
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MIMO System Technology for Wireless Communications

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microwave and Wireless Communications".

Deadline for manuscript submissions: closed (20 April 2023) | Viewed by 8423

Special Issue Editor

Prof. Dr. Dongming Wang

E-Mail Website
Guest Editor
National Mobile Communication Research Laboratory, Southeast University, Nanjing 211189, China
Interests: signal processing for wireless communications; large-scale distributed MIMO systems (cell-free massive MIMO)
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

With the commercialization of 5G, 6G has become a hot research topic in both academia and industry. From 3G to 5G, multi antenna (MIMO) technology has played an important role. It is also a key enabling technology for 6G to meet the key performance indicators, such as high-frequency spectral efficiency, a high peak data rate and ultra-high reliability. At present, the research on 6G multi antenna technology includes cellular free large-scale MIMO, reconfigurable intellegence surface (RIS) wireless communication, phased array communication, etc. This Special Issue focuses on the research of multi antenna technology in 6G, mainly including, but not limited to, the following directions:

  • Massive MIMO;
  • Cell-free massive MIMO;
  • mmWave/TeraHerz massive MIMO;
  • Reconfigurable intelligence surfaces.

Prof. Dr. Dongming Wang
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • cell-free massive MIMO
  • RIS multiple antenna technologies
  • mmWave/TeraHerz MIMO technologies

Published Papers (5 papers)

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Research

17 pages, 1153 KiB  
Article
Downlink Spectral Efficiency of Massive MIMO Systems with Mutual Coupling
by Yiru Liu, Bo Ai and Jiayi Zhang
Electronics 2023, 12(6), 1364; https://doi.org/10.3390/electronics12061364 - 13 Mar 2023
Cited by 1 | Viewed by 1399
Abstract
Massive multiple-input multiple-output (MIMO) is a profitable technique to greatly boost spectral efficiency, which has been embraced by the fifth-generation (5G) and sixth-generation (6G) mobile communication systems. By exploiting appropriate downlink precoding algorithms, base stations (BSs) equipped with a large number of antennas [...] Read more.
Massive multiple-input multiple-output (MIMO) is a profitable technique to greatly boost spectral efficiency, which has been embraced by the fifth-generation (5G) and sixth-generation (6G) mobile communication systems. By exploiting appropriate downlink precoding algorithms, base stations (BSs) equipped with a large number of antennas are able to provide service to multiple users as well as several cells at the same time and frequency. However, the mutual coupling effect due to the compact antenna array gives misleading results in massive MIMO communication systems. In this paper, we focus on the mutual coupling effect for massive MIMO systems with maximal ratio transmission (MRT), zero-forcing (ZF), regularize ZF (RZF), and minimum mean square error (MMSE) precoding to solve the mutual coupling problem. Additionally, we construct the closed-form expressions of the spectral efficiency (SE) to evaluate the effect of mutual coupling on system performance. Simulation results validate the effectiveness of the proposed mutual coupling effect assessment method and demonstrate the significant impacts of mutual coupling on massive MIMO system performance. Full article
(This article belongs to the Special Issue MIMO System Technology for Wireless Communications)
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21 pages, 9994 KiB  
Article
Compact Quad-Port MIMO Antenna with Ultra-Wideband and High Isolation
by Zhengrui He and Jie Jin
Electronics 2022, 11(20), 3408; https://doi.org/10.3390/electronics11203408 - 20 Oct 2022
Cited by 9 | Viewed by 1768
Abstract
In this paper, we propose a compact and highly isolated four-port ultra-wideband MIMO antenna. The antenna elements achieve broadband characteristics by etching a metamaterial structure on the radiating patch and stepping the coplanar waveguide feed. The test results show that the unit antenna [...] Read more.
In this paper, we propose a compact and highly isolated four-port ultra-wideband MIMO antenna. The antenna elements achieve broadband characteristics by etching a metamaterial structure on the radiating patch and stepping the coplanar waveguide feed. The test results show that the unit antenna can operate from 1.8 GHz to 16.38 GHz with an absolute bandwidth of 14.58 GHz and a relative bandwidth of 160.4% with good radiation properties and gain. After that, a compact four-cell ultra-wideband MIMO antenna is designed by using polarization diversity technology with an overall size of 51.2 mm × 51.2 mm × 1.524 mm. The MIMO antenna can operate from 1 GHz to 17 GHz with an absolute bandwidth of 16 GHz and a relative bandwidth of 177.78%. To reduce the coupling between cells, four angled slits are etched on the common ground to improve the isolation of the MIMO antennas to 27.8 dB. The performance parameters of the proposed MIMO antennas are further validated through simulation analysis and measurements. Moreover, the diversity properties of MIMO antennas are analyzed in detail, demonstrating the applicability of the proposed antennas in UWB communication systems, which can also be used for satellite mobile communications and satellite fixed communication services. Full article
(This article belongs to the Special Issue MIMO System Technology for Wireless Communications)
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18 pages, 467 KiB  
Article
Hybrid Beamforming for MISO System via Convolutional Neural Network
by Teng Zhang, Anming Dong, Chuanting Zhang, Jiguo Yu, Jing Qiu, Sufang Li and You Zhou
Electronics 2022, 11(14), 2213; https://doi.org/10.3390/electronics11142213 - 15 Jul 2022
Cited by 3 | Viewed by 1748
Abstract
Hybrid beamforming (HBF) is a promising approach to obtain a better balance between hardware complexity and system performance in massive MIMO communication systems. However, the HBF optimization problem is a challenging task due to its nonconvex property in terms of design complexity and [...] Read more.
Hybrid beamforming (HBF) is a promising approach to obtain a better balance between hardware complexity and system performance in massive MIMO communication systems. However, the HBF optimization problem is a challenging task due to its nonconvex property in terms of design complexity and spectral efficiency (SE) performance. In this work, a low-complexity convolutional neural network (CNN)-based HBF algorithm is proposed to solve the SE maximization problem under the constant modulus constraint and transmit power constraint in a multiple-input single-output (MISO) system. The proposed CNN framework uses multiple convolutional blocks to extract more channel features. Considering that the solutions for the HBF are hard to obtain, we derive an unsupervised learning mechanism to avoid any labeled data when training the constructed CNN. We discuss the performance of the proposed algorithm in terms of both the generalization ability for multiple CSIs and the specific solving ability for an individual CSI, respectively. Simulations show its advantages in both SE and complexity over other related algorithms. Full article
(This article belongs to the Special Issue MIMO System Technology for Wireless Communications)
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14 pages, 589 KiB  
Article
Performance Analysis of Cell-Free Massive MIMO System with Network-Assisted Full-Duplex under Time-Shifting Pilot Scheme
by Tao Ma, Yanfeng Hu, Zhenqi Fan, Xinjiang Xia and Dongming Wang
Electronics 2022, 11(14), 2171; https://doi.org/10.3390/electronics11142171 - 11 Jul 2022
Cited by 1 | Viewed by 1213
Abstract
A network-assisted full-duplex (NAFD) system based on a cell-free (CF) massive multiple-input, multiple-output (MIMO) framework has been proposed to satisfy the demands of higher data transmission rates and efficient communication. However, pilot contamination may occur due to the reuse of pilot sequences in [...] Read more.
A network-assisted full-duplex (NAFD) system based on a cell-free (CF) massive multiple-input, multiple-output (MIMO) framework has been proposed to satisfy the demands of higher data transmission rates and efficient communication. However, pilot contamination may occur due to the reuse of pilot sequences in a massive MIMO. With this consideration, we raise an asynchronous channel estimation method based on an uplink and downlink time-shifting pilot-sending scheme, which is able to avoid pilot sequence reuse when obtaining channel state information (CSI), while the data signals could be transmitted simultaneously at the same frequency. The transmission processes of the proposed method above are divided into three phases, including pilot phase, estimation phase, and data phase, in chronological order. When the uplink is in pilot phase, the corresponding downlink is in data phase and vice versa. After the channel state information estimation, both uplinks and downlinks are in data phase. The maximum ratio combination (MRC) receiver and the maximum ratio transmission (MRT) precoding are adopted in the uplink and downlink. The closed-form expressions are derived based on large-scale random matrix theory. We compared our asymptotic results with practical results in simulation, and find that they are well matched. Moreover, the proposed method is superior to the normal time-division duplex (TDD) system. Full article
(This article belongs to the Special Issue MIMO System Technology for Wireless Communications)
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16 pages, 513 KiB  
Article
Joint User Scheduling and Resource Allocation in Distributed MIMO Systems with Multi-Carriers
by Yinglan Bu, Jiaying Zong, Xinjiang Xia, Yang Liu, Fengyi Yang and Dongming Wang
Electronics 2022, 11(12), 1836; https://doi.org/10.3390/electronics11121836 - 09 Jun 2022
Cited by 2 | Viewed by 1328
Abstract
Compared with the traditional collocated multi-input multi-output system (C-MIMO), distributed MIMO (D-MIMO) systems have the advantage of higher throughput and coverage, making them strong candidates for next-generation communication architecture. As a practical implementation of a D-MIMO cooperative network, the multi-TRP (multiple transmission/reception point) [...] Read more.
Compared with the traditional collocated multi-input multi-output system (C-MIMO), distributed MIMO (D-MIMO) systems have the advantage of higher throughput and coverage, making them strong candidates for next-generation communication architecture. As a practical implementation of a D-MIMO cooperative network, the multi-TRP (multiple transmission/reception point) system becomes a hotspot in the research of advanced 5G. Different from previous research on a cooperative D-MIMO network with single narrowband transmission, this paper proposes a joint optimization scheme to address the user scheduling problem along with carrier allocation to maximize the total spectral efficiency (SE) in the downlink of coherent multi-TRP systems with multi-carriers. We establish a joint optimization model of user scheduling and resource allocation to maximize the system spectral efficiency under the constraints of power consumption and the backhaul capacity limits at each RAU (remote antenna unit), as well as the QoS (quality of service) requirement at each user. Since the optimization model is both non-covex and non-smooth, a joint optimization algorithm is proposed to solve this non-convex combinatorial optimization problem. We first smooth the mixed-integer problem by employing penalty functions, and after decoupling the coupled variables by introducing auxiliary variables, the original problem is transformed into a series of tractable convex optimization problems by using successive convex approximation (SCA). Numerical results demonstrate that the proposed joint optimization algorithm for user scheduling and resource allocation can reliably converge and achieve a higher system SE than the general multi-TRP system without carrier allocation, and this advantage is more pronounced under a higher backhaul capacity or higher power consumption constraints. Full article
(This article belongs to the Special Issue MIMO System Technology for Wireless Communications)
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