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Next Generation Radio Communication Technologies

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Communications".

Deadline for manuscript submissions: closed (10 November 2022) | Viewed by 17475
Please feel free to contact Guest Editors or Special Issue Editor ([email protected]) for any queries.

Special Issue Editors


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Instituto de Telecomunicações, Departamento de Eletrónica, Telecomunicações e Informática, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
Interests: Software Defined Radio; Radio Access Networks; Embedded Systems
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Instituto de Telecomunicações, Departamento de Eletrónica, Telecomunicações e Informática, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
Interests: radio-frequency systems; antennas; wireless power transfer

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Guest Editor
Instituto de Telecomunicações, Departamento de Eletrónica, Telecomunicações e Informática, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
Interests: Digital Communications; Wireless Communications; Communication Theory

Special Issue Information

Dear Colleagues,

The fifth generation (5G) of wireless communications is currently being deployed to support three classes of services with heterogeneous requirements and a variety of innovative vertical uses cases: enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC). Simultaneously, a brand-new set of demanding use cases and technology innovations is leading to the development of the sixth generation (5G+/6G) of wireless communications. In 5G+/6G networks, added features such as support for intelligent connected devices, even higher user data rates, and service interconnectivity are expected, requiring the coexistence of the three aforementioned heterogeneous services. In these new scenarios, features such as extreme broadband, higher performance, lower end-to-end latency, greater autonomy, and near instant and reliable connectivity to enable massive data exchange are necessary. In other words, 5G+/6G technology for verticals and advanced applications, enabled by eMBB, mMTC and URLLC integration, is supposed to be faster and provide services of higher quality, greater agility and efficiency, and flexible spectrum management, enabling higher degrees of resource sharing and efficiency. However, this results in highly advanced challenges. Thus, in order to deal with the huge complexity and find an optimal solution to the demanding challenges, artificial intelligence (AI) can be a key technology in many applications, mainly due to its adaptive capabilities, and it has been considered in many analytical, simulation, and experimental works.

In this context, this Special Issue aims to gather innovative contributions concerning the next generation of radio communication technologies. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

- 5G open issues on mMTC and URLLC;

- Energy-efficient communications, including distributed backscatter and battery-less devices;

- Adaptive and highly efficient physical layer waveforms, including modulation, coding, and multiple access;

- Advances on (full-)duplex techniques;

- Cell-free and massive MIMO technology;

- Adaptive resource management and scheduling;

- Smart and/or dynamic spectrum assignment and sharing;

- Millimeter wave technology and terahertz bands;

- Novel antenna technologies;

- Comprehensive AI for planning, prediction, detection, and self-healing;

- Advanced signal processing techniques, devices, and tools;

- Software radios and smart radios;

- Next-generation radio access networks;

- Non-terrestrial networks;

- Open specifications, architectures, and interfaces.

Dr. Arnaldo Silva Rodrigues de Oliveira
Prof. Dr. Nuno Carvalho
Dr. Hugerles Sales Silva
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 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.

Published Papers (7 papers)

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Research

14 pages, 4751 KiB  
Article
User-Driven Relay Beamforming for mmWave Massive Analog-Relay MIMO
by Masashi Iwabuchi, Yoghitha Ramamoorthi and Kei Sakaguchi
Sensors 2023, 23(2), 1034; https://doi.org/10.3390/s23021034 - 16 Jan 2023
Cited by 3 | Viewed by 1480
Abstract
Sixth-generation mobile communication (6G) aims to further improve capacity and reliability by controlling the radio propagation environment. Millimeter wave (mmWave) high-frequency band communication offers large bandwidth at the cost of high attenuation, even for smaller distances. Due to this, fewer multiple input multiple [...] Read more.
Sixth-generation mobile communication (6G) aims to further improve capacity and reliability by controlling the radio propagation environment. Millimeter wave (mmWave) high-frequency band communication offers large bandwidth at the cost of high attenuation, even for smaller distances. Due to this, fewer multiple input multiple outputs (MIMO) multiplexing is possible at the base station (BS). Distributed analog relay nodes with beamforming capability improve the received power and MIMO multiplexing of mmWave communication. Due to limited signal processing, the analog relay node cannot perform beam search and tracking using these mmWave reference signals. The beam search and tracking are possible at BS or user equipment at the cost of increased control overhead. To reduce this overhead and provide relay-based 6G communication, we propose user-driven relay beamforming methods which can obtain the benefits of a massive analog relay MIMO. Assuming vehicular-to-everything (V2X) as a 6G application, we considered a relay-beam control method that uses the user information (location, velocity, acceleration, and direction of the terminal) contained in intelligent transport systems (ITS) messages called Cooperative Awareness Message (CAM). Simulation results show that the proposed method significantly reduces the overhead and the obtains benefits of the massive analog-relay MIMO. Furthermore, the accuracy of CAM’s location information, the control period, and the effects of UE mobility are evaluated and presented. The results also show that the proposed method can work effectively in future V2X applications. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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15 pages, 401 KiB  
Article
Genetic Approach for Joint Transmission Grouping in Next-Generation Cellular Networks
by Yu-Po Kuo, Ya-Ju Yu, Tzung-Pei Hong and Wei-Kuang Lai
Sensors 2022, 22(19), 7147; https://doi.org/10.3390/s22197147 - 21 Sep 2022
Viewed by 918
Abstract
Coordinated multipoint joint transmission (JT) is one of the critical downlink transmission technologies to improve network throughput. However, multiple cells in a JT group should have the same user data to transmit simultaneously, resulting in a considerable backhaul burden. Even when cells are [...] Read more.
Coordinated multipoint joint transmission (JT) is one of the critical downlink transmission technologies to improve network throughput. However, multiple cells in a JT group should have the same user data to transmit simultaneously, resulting in a considerable backhaul burden. Even when cells are already equipped with caches in fifth-generation networks, JT groups, without effectively utilizing the caching data, still cause unnecessary backhaul data traffic. In this article, we investigate the JT grouping problem with the consideration of caches at cells. Then, we propose a genetic approach to solve the above problem with the objective of minimizing the amount of backhaul data traffic subject to the data-rate requirement of each user. The simulation results show that our proposed generic algorithm can significantly decrease the backhaul bandwidth consumption compared to the two baselines. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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22 pages, 1665 KiB  
Article
Characteristics of Channel Eigenvalues and Mutual Coupling Effects for Holographic Reconfigurable Intelligent Surfaces
by Shu Sun and Meixia Tao
Sensors 2022, 22(14), 5297; https://doi.org/10.3390/s22145297 - 15 Jul 2022
Cited by 7 | Viewed by 2478
Abstract
As a prospective key technology for the next-generation wireless communications, reconfigurable intelligent surfaces (RISs) have gained tremendous research interest in both the academia and industry in recent years. Only limited knowledge, however, has been obtained about the channel eigenvalue characteristics and spatial degrees [...] Read more.
As a prospective key technology for the next-generation wireless communications, reconfigurable intelligent surfaces (RISs) have gained tremendous research interest in both the academia and industry in recent years. Only limited knowledge, however, has been obtained about the channel eigenvalue characteristics and spatial degrees of freedom (DoF) of systems containing RISs, especially when mutual coupling (MC) is present between the array elements. In this paper, we focus on the small-scale spatial correlation and eigenvalue properties excluding and including MC effects, for RISs with a quasi-continuous aperture (i.e., holographic RISs). Specifically, asymptotic behaviors of far-field and near-field eigenvalues of the spatial correlation matrix of holographic RISs without MC are first investigated, where the counter-intuitive observation of a lower DoF with more elements is explained by leveraging the power spectrum of the spatial correlation function. Second, a novel metric is proposed to quantify the inter-element correlation or coupling strength in RISs and ordinary antenna arrays. Furthermore, in-depth analysis is performed regarding the MC effects on array gain, effective spatial correlation, and eigenvalue architectures for a variety of element intervals when a holographic RIS works in the radiation and reception mode, respectively. The analysis and numerical results demonstrate that a considerable amount of the eigenvalues of the spatial correlation matrix correspond to evanescent waves that are promising for near-field communication and sensing. More importantly, holographic RISs can potentially reach an array gain conspicuously larger than conventional arrays by exploiting MC, and MC has discrepant impacts on the effective spatial correlation and eigenvalue structures at the transmitter and receiver. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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19 pages, 694 KiB  
Article
Enhanced Angle-of-Arrival and Polarization Parameter Estimation Using Localized Hybrid Dual-Polarized Arrays
by Xiaolu Yu, Hang Li, Jian Andrew Zhang, Xiaojing Huang and Zhiqun Cheng
Sensors 2022, 22(14), 5207; https://doi.org/10.3390/s22145207 - 12 Jul 2022
Viewed by 1177
Abstract
The millimeter wave (mmWave) channel is dominated by line-of-sight propagation. Therefore, the acquisition of angle-of-arrival (AoA) and polarization state of the wave is of great significance to the receiver. In this paper, we investigate AoA and polarization estimation in a mmWave system employing [...] Read more.
The millimeter wave (mmWave) channel is dominated by line-of-sight propagation. Therefore, the acquisition of angle-of-arrival (AoA) and polarization state of the wave is of great significance to the receiver. In this paper, we investigate AoA and polarization estimation in a mmWave system employing dual-polarized antenna arrays. We propose an enhanced AoA estimation method using a localized hybrid dual-polarized array for a polarized mmWave signal. The use of dual-polarized arrays greatly improves the calibration of differential signals and the signal-to-noise ratio (SNR) of the phase offset estimation between adjacent subarrays. Given the estimated phase offset, an initial AoA estimate can be obtained, and is then used to update the phase offset estimation. This leads to a recursive estimation with improved accuracy. We further propose an enhanced polarization estimation method, which uses the power of total received signals at dual-polarized antennas to compute the cross-correlation-to-power ratio instead of using only one axis dipole. Thus the accuracy of polarization parameter estimation is improved. We also derive a closed-form expression for mean square error lower bounds of AoA estimation and present an average SNR analysis for polarization estimation performance. Simulation results demonstrate the superiority of the enhanced AoA and polarization parameter estimation methods compared to the state of the art. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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12 pages, 1466 KiB  
Communication
Novel Receive Antenna Selection Scheme for Precoding-Aided Spatial Modulation with Lattice Reduction
by Sangchoon Kim
Sensors 2022, 22(9), 3575; https://doi.org/10.3390/s22093575 - 07 May 2022
Cited by 1 | Viewed by 1423
Abstract
In this paper, a new receive antenna subset (RAS) selection scheme is proposed for precoding-aided spatial modulation (PSM). First, a lattice reduction (LR)-based precoder is employed instead of a conventional zero-forcing (ZF) precoder. It is analytically shown that a full diversity gain can [...] Read more.
In this paper, a new receive antenna subset (RAS) selection scheme is proposed for precoding-aided spatial modulation (PSM). First, a lattice reduction (LR)-based precoder is employed instead of a conventional zero-forcing (ZF) precoder. It is analytically shown that a full diversity gain can be achieved by the LR-based ZF precoder without RAS selection. Then, an optimal LR-based RAS selection criterion is derived for the over-determined LR-based PSM systems, and a suboptimal selection algorithm is additionally presented. It is also shown that optimal and suboptimal RAS selection algorithms based on LR improve the BER performance of the LR-based PSM system. Further, the overall diversity order of the over-determined LR-based PSM systems with optimal LR-based RAS selection is analyzed. Finally, diversity analysis and simulation results show that the LR-ZF-based PSM system with optimal LR-based RAS selection outperforms the conventional ZF-based PSM system with conventional optimal RAS selection. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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17 pages, 846 KiB  
Article
Capacity Performance for Full-Duplex Multihop Wireless Networks Using Channel Interference Balancing Allocation Scheme
by Aung Thura Phyo Khun, Yuto Lim and Stepan Kucera
Sensors 2022, 22(9), 3554; https://doi.org/10.3390/s22093554 - 07 May 2022
Viewed by 1363
Abstract
Full-duplex (FD) communication has been attractive as one of the research interests related to spectrum utilization for wireless networks from the previous evolution of communication systems. Previous studies discuss the realization of the FD system by focusing on self-interference cancellation and transmit power [...] Read more.
Full-duplex (FD) communication has been attractive as one of the research interests related to spectrum utilization for wireless networks from the previous evolution of communication systems. Previous studies discuss the realization of the FD system by focusing on self-interference cancellation and transmit power control in low-power wireless network scenarios. Today, capacity maximization is a key challenge in FD multihop wireless networks, in which the multi-channel allocation may lead to imbalance interference power due to the different number of simultaneous transmissions and its group selection that occurred on the same sub-channels. In this paper, we focus on the capacity maximization of the FD system by considering the influence of total interference power on each sub-channel and how to balance by selecting the different number of simultaneous transmissions to form a group that leads to a minimum difference in the total interference power on those sub-channels. Therefore, a channel interference balancing allocation (CIBA) scheme for balancing the total interference power in the multi-channel multihop wireless networks is proposed and further investigated by the idea of cooperative transmission. We also adopt the concept of interference distance to overcome the interference balancing problem of the proposed CIBA scheme. Performance evaluation results reveal that the proposed CIBA scheme achieves lesser total interference power and higher achievable capacity than other fixed channel allocation schemes. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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14 pages, 1179 KiB  
Article
Toward Modular and Flexible Open RAN Implementations in 6G Networks: Traffic Steering Use Case and O-RAN xApps
by Marcin Dryjański, Łukasz Kułacz and Adrian Kliks
Sensors 2021, 21(24), 8173; https://doi.org/10.3390/s21248173 - 07 Dec 2021
Cited by 45 | Viewed by 6954
Abstract
The development of cellular wireless systems has entered the phase when 5G networks are being deployed and the foundations of 6G solutions are being identified. However, in parallel to this, another technological breakthrough is observed, as the concept of open radio access networks [...] Read more.
The development of cellular wireless systems has entered the phase when 5G networks are being deployed and the foundations of 6G solutions are being identified. However, in parallel to this, another technological breakthrough is observed, as the concept of open radio access networks is coming into play. Together with advancing network virtualization and programmability, this may reshape the way the functionalities and services related to radio access are designed, leading to modular and flexible implementations. This paper overviews the idea of open radio access networks and presents ongoing O-RAN Alliance standardization activities in this context. The whole analysis is supported by a study of the traffic steering use case implemented in a modular way, following the open networking approach. Full article
(This article belongs to the Special Issue Next Generation Radio Communication Technologies)
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