Special Issue "Massive MIMO Systems for 5G and beyond Networks: Latest Advances and Prospects"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Electrical, Electronics and Communications Engineering".

Deadline for manuscript submissions: closed (15 September 2022) | Viewed by 13659

Special Issue Editor

Dr. Mario Marques Da Silva
E-Mail Website
Guest Editor
1. Institute of Telecommunications, 1049-001 Lisboa, Portugal
2. Department of Engineering and Computer Sciences, Autonoma University of Lisbon, 1150-293 Lisboa, Portugal
Interests: cellular communications; 6G and beyond; massive-MIMO; millimeter-wave communications; block transmission techniques; NOMA, LIS & RIS systems
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Special Issue Information

Dear Colleagues,

Transmission techniques, such as massive multiple-input multiple-output (MIMO), non-orthogonal multiple access (NOMA), block transmission techniques, or millimeter-wave communications (mm-Wave) are expected to be a crucial part of 5G (Fifth Generation) systems and beyond. Similar techniques are being adopted by IEEE 802.11 standards, such as in 802.11ad, where orthogonal frequency-division multiple access (OFDMA), mm-Wave, and massive MIMO (m-MIMO) is utilized. However, mm-Wave transmissions have significant problems, such as high free-space path losses, very small diffraction effects, huge losses due to obstacles and implementation difficulties, namely with power amplification. On the other hand, small wavelengths mean that we can have small antennas and small-sized antenna aggregates with a large number of elements, facilitating the deployment of m-MIMO schemes. The use of multiple antennas at both the transmitter and receiver aims to improve performance or to increase the symbol rate of systems, but it usually requires higher implementation complexity. m-MIMO schemes involving several tens or even hundreds of antenna elements are central technologies of 5G systems, where higher capacity and spectral efficiency are required, as compared to previous systems, but where low complexity is an important issue. Due to the existence of millions of devices, spectrum is becoming a scarce resource. NOMA is an alternative multiple access technique, which tends to present better spectral efficiency and cell capacity, but clustering is still a limitation, and coordination between users (coordinated NOMA) makes it more effective.

While 5G requirements are achieved based on mm-Wave and m-MIMO, 6G must incorporate new concepts and frequency bands not yet considered for cellular communications. This includes Visible Light Communications (VLC) and Terahertz bands (100 GHz – 10 THz), enabling data rates in the order of 1 Tbps (nomadic) or 1 Gbps (mobile), with improved energy and spectral efficiencies. VLC is a mature communication technique well suited for short range coverage, though susceptible to interferences, such as from the sun. On the other hand, flying vehicles, such as drones, alongside with a communications paradigm based on heterogenous networks (conventional cells, Vehicle-to-Everything communications [V2X], IoT, drones, balloons, satellites, etc.), will require a three-dimensional (3D) network architecture, with 3D coverage, instead of 2-dimensional, as considered by 5G. Mobility speeds of up to 1000 km/h are also expected to be a requirement of 6G.

This Special Issue aims to provide an overview of 5G communications and beyond, including the perspectives for 6G communications, in terms of network, services, and requirements, while describing advances in transmission techniques foreseen for future updates of 5G. All new ideas about how to improve performance, capacity, and/or spectrum efficiency of transmission techniques for 5G and beyond, while keeping computational cost at an acceptable level are most welcome. Contributions to this Special Issue should provide an overview of how the proposed transmission techniques bring added value to the advances of cellular communications, in terms of performance and/or advanced requirements.

Prof. Dr. Mario Marques Da Silva
Guest Editor

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Keywords

  • 5G and beyond
  • massive MIMO
  • millimeter-wave communications
  • block transmission techniques
  • non-orthogonal multiple access
  • 6G Communications
  • visible light communications and terahertz bands

Published Papers (9 papers)

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Research

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Article
Energy-Efficient User Pairing for Downlink NOMA in Massive MIMO Networks
Appl. Sci. 2022, 12(11), 5421; https://doi.org/10.3390/app12115421 - 27 May 2022
Cited by 1 | Viewed by 587
Abstract
The motivations for deploying energy and spectral-efficient network architectures are the high energy consumption and the need for more spectral resources in modern cellular networks. The key method to solve the energy efficiency EE maximization problem of the downlink non-orthogonal multiple access (NOMA)-based [...] Read more.
The motivations for deploying energy and spectral-efficient network architectures are the high energy consumption and the need for more spectral resources in modern cellular networks. The key method to solve the energy efficiency EE maximization problem of the downlink non-orthogonal multiple access (NOMA)-based massive MIMO system is to decouple it into user pairing and efficient power allocation problems. This work studies the performance of three main pairing methods in NOMA-based networks: Hungarian, Gale–Shapley, and correlation-based approaches. Firstly, we provide a mathematical analysis for EE of downlink NOMA in a massive MIMO system for the non-line of sight (NLoS) channel model with perfect successive interference cancellation (SIC). Finally, the sequential convex programming (SCP) approach is used to tackle the power allocation problem. Simulation results show that the Hungarian algorithm for pairing plus SCP for power allocation (Hungarian algorithm-SCP) achieves the highest energy efficiency among all the three pairing algorithms with an identical performance to joint user and resource block association with power allocation (joint user-RB PA) algorithm but with much lower computational complexity and outperforms the NOMA SCP greedy algorithm (NOMA-SCP-GA). Full article
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Article
A Wideband Bear-Shaped Compact Size Implantable Antenna for In-Body Communications
Appl. Sci. 2022, 12(6), 2859; https://doi.org/10.3390/app12062859 - 10 Mar 2022
Cited by 5 | Viewed by 1574
Abstract
Biomedical implantable antennas play a vital role in medical telemetry applications. These types of biomedical implantable devices are very helpful in improving and monitoring patients’ living situations on a daily basis. In the present paper, a miniaturized footprint, thin-profile bear-shaped in-body antenna operational [...] Read more.
Biomedical implantable antennas play a vital role in medical telemetry applications. These types of biomedical implantable devices are very helpful in improving and monitoring patients’ living situations on a daily basis. In the present paper, a miniaturized footprint, thin-profile bear-shaped in-body antenna operational at 915 MHz in the industrial, scientific, and medical (ISM) band is proposed. The design is a straightforward bear-shaped truncated patch excited by a 50-Ω coaxial probe. The radiator is made up of two circular slots and one rectangular slot at the feet of the patch, and the ground plane is sotted to achieve a broadsided directional radiation pattern, imprinted on a Duroid RT5880 roger substrate with a typical 0.254-mm thickness ( ϵr = 2.2, tan δ = 0.0009). The stated antenna has a complete size of 7 mm × 7 mm × 0.254 mm and, in terms of guided wavelength, of 0.027λg × 0.027λg × 0.0011λg. When operating inside skin tissues, the antenna covers a measured bandwidth from 0.86 GHz to 1.08 GHz (220 MHz). The simulations and experimental outcomes of the stated design are in proper contract. The obtained results show that the calculated specific absorption rate (SAR) values inside skin of over 1 g of mass tissue is 8.22 W/kg. The stated SAR values are lower than the limitations of the federal communications commission (FCC). Thus, the proposed miniaturized antenna is an ultimate applicant for in-body communications. Full article
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Article
System-Level Assessment of a C-RAN based on Generalized Space–Frequency Index Modulation for 5G New Radio and Beyond
Appl. Sci. 2022, 12(3), 1592; https://doi.org/10.3390/app12031592 - 02 Feb 2022
Cited by 1 | Viewed by 864
Abstract
Index modulation (IM) has been attracting considerable research efforts in recent years as it is considered a promising technology that can enhance spectral and energy efficiency and help cope with the rising demand of mobile traffic in future wireless networks. In this paper, [...] Read more.
Index modulation (IM) has been attracting considerable research efforts in recent years as it is considered a promising technology that can enhance spectral and energy efficiency and help cope with the rising demand of mobile traffic in future wireless networks. In this paper, we propose a cloud radio access network (C-RAN) suitable for fifth-generation (5G) and beyond systems, where the base stations (BSs) and access points (APs) transmit multidimensional IM symbols, which we refer to as precoding-aided transmitter-side generalized space–frequency IM (PT-GSFIM). The adopted PT-GSFIM approach is an alternative multiuser multiple-input multiple-output (MU-MIMO) scheme that avoids multiuser interference (MUI) while exploiting the inherent diversity in frequency-selective channels. To validate the potential gains of the proposed PT-GSFIM-based C-RAN, a thorough system-level assessment is presented for three different three-dimensional scenarios taken from standardized 5G New Radio (5G NR), using two different numerologies and frequency ranges. Throughput performance results indicate that the 28 GHz band in spite of its higher bandwidth and higher achieved throughput presents lower spectral efficiency (SE). The 3.5 GHz band having lower bandwidth and lower achieved throughput attains higher SE. Overall, the results indicate that a C-RAN based on the proposed PT-GSFIM scheme clearly outperforms both generalized spatial modulation (GSM) and conventional MU-MIMO, exploiting its additional inherent frequency diversity. Full article
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Article
Performance Analysis of Rate Splitting in Massive MIMO Systems with Low Resolution ADCs/DACs
Appl. Sci. 2021, 11(20), 9409; https://doi.org/10.3390/app11209409 - 11 Oct 2021
Viewed by 923
Abstract
In this paper, we propose rate-splitting (RS) multiple access to mitigate the effects of quantization noise (QN) inherent in low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). We consider the downlink (DL) of a multiuser massive multiple-input multiple-output (MIMO) system where the base [...] Read more.
In this paper, we propose rate-splitting (RS) multiple access to mitigate the effects of quantization noise (QN) inherent in low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). We consider the downlink (DL) of a multiuser massive multiple-input multiple-output (MIMO) system where the base station (BS) is equipped with low-resolution ADCs/DACs. The BS employs the RS scheme for data transmission. Under imperfect channel state information (CSI), we characterize the spectral efficiency (SE) and energy efficiency (EE) by deriving the asymptotic signal-to-interference-and-noise ratio (SINR). For 1-bit resolution, the QN is very high, and the RS scheme shows no rate gain over the non-RS scheme. As the ADC/DAC resolution increases (i.e., 2–3 bits), the RS scheme achieves higher SE in the high signal-to-noise ratio (SNR) regime compared to that of the non-RS scheme. For a 3-bit resolution, the number of antennas can be reduced by 27% in the RS scheme to achieve the same SE as the non-RS scheme. Low-resolution DACs degrades the system performance more than low-resolution ADCs. Hence, it is preferable to equip the system with low-resolution ADCs than low-resolution DACs. The system achieves the best SE/EE tradeoff for 4-bit resolution ADCs/DACs. Full article
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Article
On the Performance of LDPC-Coded Massive MIMO Schemes with Power-Ordered NOMA Techniques
Appl. Sci. 2021, 11(18), 8684; https://doi.org/10.3390/app11188684 - 17 Sep 2021
Cited by 5 | Viewed by 928
Abstract
This article studies the power-ordered Non-Orthogonal Multiple Access (NOMA) techniques associated with Low-Density Parity-Check (LDPC) codes, adopted for use in the fifth generation of cellular communications (5G). Both conventional and cooperative NOMA are studied, associated with Single Carrier with Frequency Domain Equalization (SC-FDE) [...] Read more.
This article studies the power-ordered Non-Orthogonal Multiple Access (NOMA) techniques associated with Low-Density Parity-Check (LDPC) codes, adopted for use in the fifth generation of cellular communications (5G). Both conventional and cooperative NOMA are studied, associated with Single Carrier with Frequency Domain Equalization (SC-FDE) and massive Multiple-Input Multiple-Output (MIMO). Billions of Internet of Things (IoT) devices are aimed to be incorporated by the Fourth Industrial Revolution, requiring more efficient use of the spectrum. NOMA techniques have the potential to support that goal and represent strong candidates for incorporation into future releases of 5G. This article shows that combined schemes associated with both conventional and cooperative LDPC-coded NOMA achieve good performance while keeping the computational complexity at an acceptable level. Full article
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Article
Performance Analysis of Two-Hop mmWave Relay Nodes over the 5G NR Uplink Signal
Appl. Sci. 2021, 11(13), 5828; https://doi.org/10.3390/app11135828 - 23 Jun 2021
Cited by 3 | Viewed by 1358
Abstract
In this paper, the uplink in a two-hop 5G new radio co-operative system using Relay Nodes (RNs) in millimeter bands has been simulated and studied. We focus on an uplink Amplify-and-Forward Relay Node (A&F RN) and Decode-and-Forward Relay Node (D&F RN) with an [...] Read more.
In this paper, the uplink in a two-hop 5G new radio co-operative system using Relay Nodes (RNs) in millimeter bands has been simulated and studied. We focus on an uplink Amplify-and-Forward Relay Node (A&F RN) and Decode-and-Forward Relay Node (D&F RN) with an mmWave-band transceiver chain (Tx/Rx). We study two uplink mmWave MIMO D&F relaying protocols assuming, firstly, the complete knowledge of the uplink channel and, secondly, the uplink channel estimation through a Least Square (LS) algorithm. To verify the benefits of the proposed uplink mmWave MIMO co-operative network, a link-level co-operative simulator has been developed using MatlabTM and SimulinkTM software, where an indoor-to-outdoor scenario and mmWave transceiver with off-the shelf components are considered. The main novelty of this link-level co-operative simulator and the implemented relay nodes is the usage of signals with 5G NR features, such as UL-SCH transport channel coding and PUSCH generation, which are the other main contributions of this article. Based on the numerical results in terms of the achievable Bit Error Rate (BER) and throughput, we show that the two-hop uplink co-operative network substantially improves the performance in the communications between the NR-User Equipment (NR-UE) and the logical 5G Radio Node (gNodeB). For example, the results from using uplink mmWave NR-D&F protocols far exceed those achieved with the uplink mmWave NR-A&F algorithm; in the case of the 64-QAM modulation scheme for the SISO technique, an improvement of 6.5 Mbps was achieved using the D&F PCE protocol, taking into account that the 256-QAM constellation is higher by 4.05 Mbps. On the other hand, an average throughput enhancement of 28.77 Mbps was achieved when an uplink mmWave (2 × 4 × 4) D&F PCE strategy was used versus an uplink mmWave SISO D&F LS protocol for a Signal-to-Noise Ratio (SNR) = 20 dB and 64-QAM signal. However, an improvement of 56.42 Mbps was reached when a 256-QAM modulation scheme was employed. Furthermore, this paper introduces the first study to develop an uplink mmWave MIMO 5G co-operative network platform through a Software Defined Radio (SDR) from a practical implementation point of view. Full article
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Article
Joint Channel Estimation and Synchronization Techniques for Time-Interleaved Block-Windowed Burst OFDM
Appl. Sci. 2021, 11(10), 4403; https://doi.org/10.3390/app11104403 - 12 May 2021
Viewed by 1011
Abstract
From a conceptual perspective, beyond-5G technologies promise to deliver very low latency, even higher data rates, and ultrareliable connections for future generations of communication systems. Modulation schemes based on orthogonal frequency-domain multiplexing (OFDM) can accommodate these requirements for wireless systems. Several hybrid OFDM-based [...] Read more.
From a conceptual perspective, beyond-5G technologies promise to deliver very low latency, even higher data rates, and ultrareliable connections for future generations of communication systems. Modulation schemes based on orthogonal frequency-domain multiplexing (OFDM) can accommodate these requirements for wireless systems. Several hybrid OFDM-based systems, such as the time-interleaved block-windowed burst–OFDM (TIBWB–OFDM), are capable of achieving even better spectral confinement and power efficiency. This paper addresses the implementation of the TIBWB–OFDM system in more realistic and practical wireless link scenarios by addressing the challenges of proper and reliable channel estimation and frame synchronization. We propose to incorporate a preamble formed by optimal correlation training sequences such as the Zadoff–Chu (ZC) sequences. The added ZC preamble sequence is used to jointly estimate the frame beginning through signal-correlation strategies and a threshold decision device, and acquire channel-state information (CSI) by employing estimators on the basis of the preamble sequence and transmitted data. The employed receiver estimators show that it is possible to detect the TIBWB–OFDM frame beginning and highlight the robustness of the TIBWB–OFDM technique to imperfect channel estimations by showing that it can provide comparatively close BER performance to the one where the CSI is perfectly known. Full article
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Article
Power-Ordered NOMA with Massive MIMO for 5G Systems
Appl. Sci. 2021, 11(8), 3541; https://doi.org/10.3390/app11083541 - 15 Apr 2021
Cited by 9 | Viewed by 1536
Abstract
The aim of this article is to study the conventional and cooperative power-order Non-Orthogonal Multiple Access (NOMA) using the Single Carrier with Frequency Domain Equalization (SC-FDE) block transmission technique, associated with massive Multiple-Input Multiple-Output (MIMO), evidencing its added value in terms of spectral [...] Read more.
The aim of this article is to study the conventional and cooperative power-order Non-Orthogonal Multiple Access (NOMA) using the Single Carrier with Frequency Domain Equalization (SC-FDE) block transmission technique, associated with massive Multiple-Input Multiple-Output (MIMO), evidencing its added value in terms of spectral efficiency of such combined scheme. The new services provided by Fifth Generation of Cellular Communications (5G) are supported by new techniques, such as millimeter waves (mm-wave), alongside the conventional centimeter waves and by massive MIMO (m-MIMO) technology. NOMA is expected to be incorporated in future releases of 5G, as it tends to achieve a capacity gain, highly required for the massive number of Internet of things (IoT) devices, namely to support an efficient reuse of limited spectrum. This article shows that the combination of conventional and cooperative NOMA with m-MIMO and SC-FDE, tends to achieve capacity gains, while the performance only suffers a moderate degradation, being an acceptable alternative for future evolutions of 5G. Moreover, it is shown that Cooperative NOMA tends to outperform Conventional NOMA. Moreover, this article shows that the Maximum Ratio Combiner (MRC) receiver is very well fitted to be combined with NOMA and m-MIMO, as it achieves a good performance while reducing the receiver complexity. Full article
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Review

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Review
Towards Enhanced Mobile Broadband Communications: A Tutorial on Enabling Technologies, Design Considerations, and Prospects of 5G and beyond Fixed Wireless Access Networks
Appl. Sci. 2021, 11(21), 10427; https://doi.org/10.3390/app112110427 - 05 Nov 2021
Cited by 7 | Viewed by 3660
Abstract
There has been a growing interconnection across the world owing to various multimedia applications and services. Fixed wireless access (FWA) is an attractive wireless solution for delivering multimedia services to different homes. With the fifth-generation (5G) and beyond mobile networks, the FWA performance [...] Read more.
There has been a growing interconnection across the world owing to various multimedia applications and services. Fixed wireless access (FWA) is an attractive wireless solution for delivering multimedia services to different homes. With the fifth-generation (5G) and beyond mobile networks, the FWA performance can be enhanced significantly. However, their implementation will present different challenges on the transport network due to the incessant increase in the number of required cell-sites and the subsequent increase in the per-site requirements. This paper presents a comprehensive tutorial on the enabling technologies, design considerations, requirements, and prospects of broadband schemes. Furthermore, the related technical challenges of FWA are reviewed, and we proffer potential solutions to address them. Besides, we review various transport network options that can be employed for FWA deployment. In this regard, we offer an in-depth discussion on their related requirements for different use cases. Moreover, we give an insight into the 3GPP RAN functional split implementations and implications on the 5G FWA transport network solutions. The concepts of virtualized RANs for attending flexibly to the dynamic nature of different use cases are also presented. Full article
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