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Transmission Techniques for Future Global Mobile Systems

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

Deadline for manuscript submissions: closed (30 December 2021) | Viewed by 27024

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Special Issue Editors

Prof. Dr. Francisco Cercas

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Guest Editor

ISCTE-IUL and Instituto de Telecomunicações, 1649-026 Lisboa, Portugal
Interests: mobile and personal communications; channel coding; satellite communications; spread spectrum communications
Special Issues, Collections and Topics in MDPI journals

Dr. Rui Dinis

E-Mail Website
Guest Editor

1. Faculty of Sciences and Technology, Universidade Nova, 2829-516 Caparica, Portugal
2. Instituto de Telecomunicações, 1049-001 Lisboa, Portugal
Interests: wireless communications; wireless systems
Special Issues, Collections and Topics in MDPI journals

Dr. Nuno Souto

E-Mail Website
Guest Editor

1. ISCTE – Instituto Universitário de Lisboa, 1649-026 Lisboa, Portugal
2. Instituto de Telecomunicacoes, Lisbon, Portugal
Interests: signal processing for communications; communication signal transmission; reception and detection algorithms; channel estimation and modeling; MIMO communications; performance analysis of communication systems; optimization techniques in wireless communications; wireless, ad hoc and sensor networks

Special Issue Information

Dear Colleagues,

While 5G is progressively being implemented all around the world, it is time to develop better technologies for future communications. Requirements include ubiquitous and full connectivity anywhere in the globe, be it in places with good infrastructures, like great cities and smart cities, where a massive number of phones, sensors, drones, wearables, robots, cars, and all kinds of smart objects coexist, or in other places with little or no infrastructure, like rural places, or even at the sea, the poles or the desert, be it steady or moving at high speeds, such as on an airplane or a high-speed train.

Global coverage and high availability require a satellite component, so a distributed and decentralized infrastructure aided by artificial intelligence algorithms will decide, without the need for user intervention, the best possible resources to accomplish the required quality of service, such as high reliability, very low latency, high bandwidth, and/or other requirements. All of this must also work with high energy efficiency and minimum-security risks, so users can trust the system. Future networks and this connected way of life will become the so-called 4th utility.

For this dream to become true it is necessary to improve on the existing 5G system with new ideas and proposals, and that is the purpose of this Special Issue. We invite all the academic community, researchers, and leaders from the industry, and innovators, to contribute with great new ideas for our common and global connected world.

Prof. Francisco Cercas
Prof. Rui Dinis
Prof. Nuno Souto
Guest Editors

Manuscript Submission Information

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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.

Keywords

Beyond 5G
Reconfigurable intelligent surfaces
Radio stripes
THz communications
New waveforms and modulations
Channel coding, estimation, and tracking
Massive MIMO
Physical layer security
Simultaneous wireless information and power transference
Global mobile satellite communications

Published Papers (10 papers)

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Research

17 pages, 6770 KiB

Open AccessArticle

A Software Defined Radio Based Anti-UAV Mobile System with Jamming and Spoofing Capabilities

by Renato Ferreira, João Gaspar, Pedro Sebastião and Nuno Souto

Sensors 2022, 22(4), 1487; https://doi.org/10.3390/s22041487 - 15 Feb 2022

Cited by 17 | Viewed by 4786

Abstract

The number of incidents between unmanned aerial vehicles (UAVs) and aircrafts at airports and airfields has been increasing over the last years. To address the problem, in this paper we describe a portable system capable of protecting areas against unauthorized UAVs, which is based on the use of low-cost SDR (software defined radio) platforms. The proposed anti-UAV system supports target localization and integrates effective jamming techniques with the generation of global positioning system (GPS) spoofing signals aimed at the drone. Real-life tests of the implemented prototype have shown that the proposed approach is capable of stopping the reliable reception of radionavigation signals and can also divert or even take control of unauthorized UAVs, whose flight path depends on the information obtained by the GPS system. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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21 pages, 542 KiB

Open AccessArticle

Gibbs Sampling Detection for Large MIMO and MTC Uplinks with Adaptive Modulation

by Francisco Rosário and Francisco A. Monteiro

Sensors 2022, 22(4), 1309; https://doi.org/10.3390/s22041309 - 09 Feb 2022

Cited by 1 | Viewed by 1299

Abstract

Wireless networks beyond 5G will mostly be serving myriads of sensors and other machine-type communications (MTC), with each device having different requirements in respect to latency, error rate, energy consumption, spectral efficiency or other specifications. Multiple-input multiple-output (MIMO) systems remain a central technology towards 6G, and in cases where massive antenna arrays or cell-free networks are not possible to deploy and only moderately large antenna arrays are allowed, the detection problem at the base-station cannot rely on zero-forcing or matched filters and more complex detection schemes have to be used. The main challenge is to find low complexity, hardware feasible methods that are able to attain near optimal performance. Randomized algorithms based on Gibbs sampling (GS) were proven to perform very close to the optimal detection, even for moderately large antenna arrays, while yielding an acceptable number of operations. However, their performance is highly dependent on the chosen “temperature” parameter (TP). In this paper, we propose and study an optimized variant of the GS method, denoted by triple mixed GS, and where three distinct values for the TP are considered. The method exhibits faster convergence rates than the existing ones in the literature, hence requiring fewer iterations to achieve a target bit error rate. The proposed detector is suitable for symmetric large MIMO systems, however the proposed fixed complexity detector is highly suitable to spectrally efficient adaptively modulated MIMO (AM-MIMO) systems where different types of devices upload information at different bit rates or have different requirements regarding spectral efficiency. The proposed receiver is shown to attain quasi-optimal performance in both scenarios. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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19 pages, 7756 KiB

Open AccessArticle

A Crest Factor Reduction Technique for LTE Signals with Target Relaxation in Power Amplifier Linearization

by José Ricardo Cárdenas-Valdez, Jose Alejandro Galaviz-Aguilar, Cesar Vargas-Rosales, Everardo Inzunza-González and Leonardo Flores-Hernández

Sensors 2022, 22(3), 1176; https://doi.org/10.3390/s22031176 - 04 Feb 2022

Cited by 1 | Viewed by 4315

Abstract

The signal conditioning treatment to achieve good relation of power with radio-frequency (RF) conversion in conventional transceiver systems require precise baseband models. A developed framework is built to provide a demonstration of the modeling figures of merit with orthogonal frequency division multiplexing (OFDM) support under signal conditioning and transmission restrictions to waveforms with high peak to average power ratio (PAPR) in practical applications. Therefore, peak and average power levels have to be limited to correct high PAPR for a better suited correction power from the amplifier that can lead to compression or clipping in the signal of interest. This work presents an alternative joint crest factor reduction (CFR) algorithm to correct the performance of PAPR. A real-time field-programmable gate array (FPGA) testbed is developed to characterize and measure the behavior of an amplifier using a single-carrier 64–QAM OFDM based on long-term evolution (LTE) downlink at

2.40

GHz as stimulus, across wide modulation bandwidths. The results demonstrate that the CFR accuracy capabilities for the signal conditioning show a reliable clipping reduction to give a smooth version of the clipping signal and provide a factor of correction for the unwanted out-of-band emission validated according to the adjacent channel power ratio (ACPR), PAPR, peak power, complementary cumulative distribution function (CCDF), and error vector magnitude (EVM) figures of merit. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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19 pages, 2284 KiB

Open AccessArticle

Flow Sensing-Based Congestion Detection for D2D Streaming on a 5G gNB

by Chongdeuk Lee

Sensors 2022, 22(1), 258; https://doi.org/10.3390/s22010258 - 30 Dec 2021

Viewed by 1357

Abstract

To provide high-quality streaming services in device-to-device (D2D) communications, performance parameters such as encoding rate, decoding rate, and flow rate should be detected and monitored. The proposed algorithm provides a method to detect time streaming for traffic flows in D2D communications, and a sequence to detect rate imbalance. This paper proposes a new FS-CDA (flow sensing-based congestion detecting algorithm) to prevent high congestion rates and assist an optimized D2D streaming service in 5G-based wireless mobile networks. The proposed algorithm detects and controls flow imbalance for streaming segments during D2D communications, and it includes operations such as transmission rate monitoring, rate adjustment functions, and underflow and overflow sensing for these operations. The paper aims to effectively control traffic flow rates caused by adjacent channel bandwidth, high bit rate error, and heterogeneous radio interference, and to enhance the performance of D2D streaming services by performing such operations. The proposed algorithm for D2D streaming services is measured by deriving the individual weight of certain versions of a streaming flow. Based on the given operations, the simulation results indicated that the proposed algorithm has better performance with respect to average congestion control ratio, PSNR, and average throughput than other methods. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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15 pages, 1766 KiB

Open AccessArticle

Low-Complexity Channel Codes for Reliable Molecular Communication via Diffusion

by Sofia Figueiredo, Nuno Souto and Francisco Cercas

Sensors 2022, 22(1), 41; https://doi.org/10.3390/s22010041 - 22 Dec 2021

Cited by 1 | Viewed by 2640

Abstract

It is envisioned that healthcare systems of the future will be revolutionized with the development and integration of body-centric networks into future generations of communication systems, giving rise to the so-called “Internet of Bio-nano things”. Molecular communications (MC) emerge as the most promising way of transmitting information for in-body communications. One of the biggest challenges is how to minimize the effects of environmental noise and reduce the inter-symbol interference (ISI) which in an MC via diffusion scenario can be very high. To address this problem, channel coding is one of the most promising techniques. In this paper, we study the effects of different channel codes integrated into MC systems. We provide a study of Tomlinson, Cercas, Hughes (TCH) codes as a new attractive approach for the MC environment due to the codeword properties which enable simplified detection. Simulation results show that TCH codes are more effective for these scenarios when compared to other existing alternatives, without introducing too much complexity or processing power into the system. Furthermore, an experimental proof-of-concept macroscale test bed is described, which uses pH as the information carrier, and which demonstrates that the proposed TCH codes can improve the reliability in this type of communication channel. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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28 pages, 8957 KiB

Open AccessArticle

A Novel Signal Design and Performance Analysis in NavCom Based on LEO Constellation

by Jing Ji, Yuting Liu, Wei Chen, Di Wu, Hongyang Lu and Jiantong Zhang

Sensors 2021, 21(24), 8235; https://doi.org/10.3390/s21248235 - 09 Dec 2021

Cited by 6 | Viewed by 2519

Abstract

The mega-launch of low Earth orbit satellites (LEOs) represents a critical opportunity to integrate navigation and communication (NavCom), but first, challenges related to signal design must be overcome. This article proposes a novel signal scheme named CE-OFDM-PM. Via research on the in-band or adjacent band, it was found that the proposed signal scheme was suitable for S-band and had a wide normalized power spectrum density (PSD), high peak-to-side lobe ratio (PSR), and multiple peaks in autocorrelation. In an analysis of the simulation performance evaluation in navigation and communication, it is found that the proposed signal scheme has the potential for high accuracy, a code tracking accuracy of up to 0.85 m, a small mutual influence between the proposed signal scheme and other schemes, excellent anti-interference properties, and a better performance at both short and long distances in terms of its anti-multipath capability. Furthermore, the proposed signal scheme shows the ability to communicate between satellites and the ground and is outstanding in terms of its bit error rate (BER), CNR, and energy per bit to noise power spectral density ratio (Eb/N0). From the technical, theoretical, and application perspectives, our proposed signal scheme has potential as an alternative scheme in future BDS, PNTs, and even 5G/B5G. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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16 pages, 2491 KiB

Open AccessArticle

Performance Evaluation of GPS Auto-Surveying Techniques

by João Manito and José Sanguino

Sensors 2021, 21(21), 7374; https://doi.org/10.3390/s21217374 - 06 Nov 2021

Viewed by 2290

Abstract

With the increase in the widespread use of Global Navigation Satellite Systems (GNSS), increasing numbers of applications require precise position data. Of all the GNSS positioning methods, the most precise are those that are based in differential systems, such as Differential GNSS (DGNSS) and Real-Time Kinematics (RTK). However, for absolute positioning, the precision of these methods is tied to their reference position estimates. With the goal of quickly auto-surveying the position of a base station receiver, four positioning methods are analyzed and compared, namely Least Squares (LS), Weighted Least Squares (WLS), Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF), using only pseudorange measurements, as well as the Hatch Filter and position thresholding. The research results show that the EKF and UKF present much better mean errors than LS and WLS, with an attained precision below 1 m after about 4 h of auto-surveying. The methods that presented the best results are then tested against existing implementations, showing them to be very competitive, especially considering the differences between the used receivers. Finally, these results are used in a DGNSS test, which verifies a significant improvement in the position estimate as the base station position estimate improves. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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31 pages, 1029 KiB

Open AccessArticle

Secure Cognitive Radio-Enabled Vehicular Communications under Spectrum-Sharing Constraints

by Suneel Yadav, Anshul Pandey, Dinh-Thuan Do, Byung Moo Lee and Adão Silva

Sensors 2021, 21(21), 7160; https://doi.org/10.3390/s21217160 - 28 Oct 2021

Cited by 1 | Viewed by 1758

Abstract

Vehicular communication has been envisioned to support a myriad of essential fifth-generation and beyond use-cases. However, the increasing proliferation of smart and intelligent vehicles has generated a lot of design and infrastructure challenges. Of particular interest are the problems of spectrum scarcity and communication security. Consequently, we considered a cognitive radio-enabled vehicular network framework for accessing additional radio spectrum and exploit physical layer security for secure communications. In particular, we investigated the secrecy performance of a cognitive radio vehicular network, where all the nodes in the network are moving vehicles and the channels between them are modeled as double-Rayleigh fading. Furthermore, adopting an underlay approach, the communication between secondary nodes can be performed by employing two interference constraint strategies at the primary receiver; (1) Strategy I: the secondary transmitter power is constrained by the interference threshold of the primary receiver, and (2) Strategy II: the secondary transmitter power is constrained by both the interference threshold of the primary receiver and the maximum transmit power of the secondary network. Under the considered strategies, we derive the exact secrecy outage probability (SOP) and ergodic secrecy capacity (ESC) expressions over double-Rayleigh fading. Moreover, by analyzing the asymptotic SOP behavior, we show that a full secrecy diversity of 1 can be achieved, when the average channel gain of the main link goes to infinity with a fixed average wiretap channel gain. From the ESC analysis, it is revealed that the ESC follows a scaling law of

Θ (ln (\frac{Ω_{m}^{2}}{Ω_{e}^{2}}))

for large

Ω_{m}

and

Ω_{e}

, where

Ω_{m}

and

Ω_{e}

are the average channel gains of the main link and wiretap link. The numerical and simulation results verify our analytical findings. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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25 pages, 1513 KiB

Open AccessArticle

Dynamic Divide Grouping Non-Orthogonal Multiple Access in Terrestrial-Satellite Integrated Network

by Yanjun Yan, Huihui Xu, Ning Zhang, Guangjie Han and Mingliu Liu

Sensors 2021, 21(18), 6199; https://doi.org/10.3390/s21186199 - 16 Sep 2021

Cited by 3 | Viewed by 1860

Abstract

Non-orthogonal multiple access (NOMA) has been extensively studied to improve the performance of the Terrestrial-Satellite Integrated Network (TSIN) on account of the shortage of frequency band resources. In this paper, the terrestrial network and satellite network synergistically provide complete coverage for ground users, and based on the architecture, we first formulate a constrained optimization problem to maximize the sum rate of the TSIN under the limited spectrum resources. As the terrestrial networks and the satellite network will cause interference to each other, we first investigate the capacity performance of the terrestrial networks and the satellite networks separately, in which the optimal power control factor expression is derived. Then, by constructing the relationship model between user elevation angle, beam angle and distance, we develop a dynamic group pairing schemes to ensure the effective pairing of NOMA users. Based on the user pairing, to obtain the optimal resource allocation, a joint optimization algorithm of power allocation, beam channel and base station channel resource is proposed. Finally, simulation results are provided to evaluate the user paring scheme as well as the total system performance, in comparison with the existing works. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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26 pages, 2593 KiB

Open AccessArticle

Low Complexity Hybrid Precoding Designs for Multiuser mmWave/THz Ultra Massive MIMO Systems

by João Pedro Pavia, Vasco Velez, Renato Ferreira, Nuno Souto, Marco Ribeiro, João Silva and Rui Dinis

Sensors 2021, 21(18), 6054; https://doi.org/10.3390/s21186054 - 09 Sep 2021

Cited by 10 | Viewed by 2541

Abstract

Millimeter-wave and terahertz technologies have been attracting attention from the wireless research community since they can offer large underutilized bandwidths which can enable the support of ultra-high-speed connections in future wireless communication systems. While the high signal attenuation occurring at these frequencies requires the adoption of very large (or the so-called ultra-massive) antenna arrays, in order to accomplish low complexity and low power consumption, hybrid analog/digital designs must be adopted. In this paper we present a hybrid design algorithm suitable for both mmWave and THz multiuser multiple-input multiple-output (MIMO) systems, which comprises separate computation steps for the digital precoder, analog precoder and multiuser interference mitigation. The design can also incorporate different analog architectures such as phase shifters, switches and inverters, antenna selection and so on. Furthermore, it is also applicable for different structures, namely fully-connected structures, arrays of subarrays (AoSA) and dynamic arrays of subarrays (DAoSA), making it suitable for the support of ultra-massive MIMO (UM-MIMO) in severely hardware constrained THz systems. We will show that, by using the proposed approach, it is possible to achieve good trade-offs between spectral efficiency and simplified implementation, even as the number of users and data streams increases. Full article

(This article belongs to the Special Issue Transmission Techniques for Future Global Mobile Systems)

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