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Telecom, Volume 1, Issue 2 (September 2020) – 5 articles

Cover Story (view full-size image): A novel user pairing scheme is proposed so as to improve the performance of integrated satellite–terrestrial NOMA networks comprising of multiple ground users by enabling cooperative D2D communication among them. The objective is to identify the pairs of users that can benefit from the terrestrial cooperation combined with satellite NOMA. Power allocation for NOMA considers the achieved rates through OMA and guarantees that user pairing leads to higher rates for each pair and an overall rate increase. The impact of various system parameters has been evaluated, and guidelines are given to improve satellite–terrestrial cooperation and spectral efficiency, compared to standalone NOMA and OMA. View this paper
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24 pages, 1024 KiB  
Article
Enhanced Integrated Satellite-Terrestrial NOMA with Cooperative Device-to-Device Communication
by Michail Karavolos, Nikolaos Nomikos and Demosthenes Vouyioukas
Telecom 2020, 1(2), 126-149; https://0-doi-org.brum.beds.ac.uk/10.3390/telecom1020010 - 07 Sep 2020
Cited by 5 | Viewed by 3216
Abstract
The currently deployed terrestrial wireless networks experience difficulties while coping with the massive connectivity demands of coexisting users and devices. The addition of satellite segments has been proposed as a viable way of providing improved coverage and capacity, leading to the formation of [...] Read more.
The currently deployed terrestrial wireless networks experience difficulties while coping with the massive connectivity demands of coexisting users and devices. The addition of satellite segments has been proposed as a viable way of providing improved coverage and capacity, leading to the formation of integrated satellite-terrestrial networks. In such topologies, non-orthogonal multiple access (NOMA) can further enhance the efficient use of wireless resources by simultaneously serving multiple users. In this paper, an integrated satellite-terrestrial NOMA network is studied where cooperation between ground users is allowed, following the device-to-device (D2D) paradigm. More specifically, the proposed satellite NOMA cooperative (SANOCO) D2D scheme optimally selects pairs of users, by considering the channel conditions of the satellite and the terrestrial D2D links. In SANOCO-D2D users are served through NOMA in the satellite link, and then, if the weak user fails to decode its signal, terrestrial D2D communication is activated to maintain the total sum rate of the system. Comparisons with conventional orthogonal multiple access (OMA) and an alternative NOMA optimal user pairing scheme show that significant sum rate and spectral efficiency gains can be harvested through SANOCO-D2D under varying channel conditions and terrestrial D2D bandwidth. Full article
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12 pages, 2726 KiB  
Article
Feature Importances: A Tool to Explain Radio Propagation and Reduce Model Complexity
by Sotirios P. Sotiroudis, Sotirios K. Goudos and Katherine Siakavara
Telecom 2020, 1(2), 114-125; https://0-doi-org.brum.beds.ac.uk/10.3390/telecom1020009 - 21 Aug 2020
Cited by 12 | Viewed by 3383
Abstract
Machine learning models have been widely deployed to tackle the problem of radio propagation. In addition to helping in the estimation of path loss, they can also be used to better understand the details of various propagation scenarios. Our current work exploits the [...] Read more.
Machine learning models have been widely deployed to tackle the problem of radio propagation. In addition to helping in the estimation of path loss, they can also be used to better understand the details of various propagation scenarios. Our current work exploits the inherent ranking of feature importances provided by XGBoost and Random Forest as a means of indicating the contribution of the underlying propagation mechanisms. A comparison between two different transmitter antenna heights, revealing the associated propagation profiles, is made. Feature selection is then implemented, leading to models with reduced complexity, and consequently reduced training and response times, based on the previously calculated importances. Full article
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18 pages, 1549 KiB  
Article
Differential Evolution in Waveform Design for Wireless Power Transfer
by Pavlos Doanis, Achilles D. Boursianis, Julien Huillery, Arnaud Bréard, Yvan Duroc and Sotirios K. Goudos
Telecom 2020, 1(2), 96-113; https://0-doi-org.brum.beds.ac.uk/10.3390/telecom1020008 - 04 Aug 2020
Cited by 4 | Viewed by 2345
Abstract
The technique of transmitting multi-tone signals in a radiative Wireless Power Transfer (WPT) system can significantly increase its end-to-end power efficiency. The optimization problem in this system is to tune the transmission according to the receiver rectenna’s nonlinear behavior and the Channel State [...] Read more.
The technique of transmitting multi-tone signals in a radiative Wireless Power Transfer (WPT) system can significantly increase its end-to-end power efficiency. The optimization problem in this system is to tune the transmission according to the receiver rectenna’s nonlinear behavior and the Channel State Information (CSI). This is a non-convex problem that has been previously addressed by Sequential Convex Programming (SCP) algorithms. Nonetheless, SCP algorithms do not always attain globally optimal solutions. To this end, in this paper, we evaluate a set of Evolutionary Algorithms (EAs) with several characteristics. The performance of the optimized multi-tone transmission signals in a WPT system is assessed by means of numerical simulations, utilizing a simplified Single Input Single Output (SISO) model. From the model evaluation, we can deduce that EAs can be successfully applied to the waveform design optimization problem. Moreover, from the presented results, we can derive that EAs can obtain the optimal solutions in the tested cases. Full article
(This article belongs to the Special Issue Modern Circuits and Systems Technologies on Communications 2020)
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16 pages, 2102 KiB  
Article
Hybrid Multi-Antenna Techniques for V2X Communications—Prototyping and Experimentation
by Konstantinos Maliatsos, Leonidas Marantis, Petros S. Bithas and Athanasios G. Kanatas
Telecom 2020, 1(2), 80-95; https://0-doi-org.brum.beds.ac.uk/10.3390/telecom1020007 - 07 Jul 2020
Cited by 6 | Viewed by 4131
Abstract
The support of the connected vehicle-to-everything (V2X) vision in conjunction with intelligent transportation system applications and services constitute a major 5G objective for modern radio systems and networks. More particularly, 5G deployment will involve multiple radio access network (RAN) technologies and a massive [...] Read more.
The support of the connected vehicle-to-everything (V2X) vision in conjunction with intelligent transportation system applications and services constitute a major 5G objective for modern radio systems and networks. More particularly, 5G deployment will involve multiple radio access network (RAN) technologies and a massive machine-type communication environment, offering a simultaneously supported variety of broadcast, multicast, and unicast applications. In this article, we present an implementation of a diversity engine able to support the multi-objective, multi-RAN, multi-service V2X use cases. The engine is enhanced with the adoption of a hybrid diversity scheme that exploits the beamshaping capabilities of the reconfigurable electronically switched parasitic array radiator (ESPAR) antennas. The hybrid scheme combines conventional maximal ratio combining with beamspace diversity and it improves system performance in terms of reliability and throughput with increased signal-to-noise ratio. It was implemented and demonstrated with integration of novel printed antennas on connected, vehicle-to-vehicle (V2V)-enabled trucks in the context of the Horizon 2020 project ROADART. Full article
(This article belongs to the Special Issue Vehicular Communications)
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12 pages, 405 KiB  
Article
A LoRa-Based Linear Sensor Network for Location Data in Underground Mining
by Philip Branch, Binghao Li and Kai Zhao
Telecom 2020, 1(2), 68-79; https://0-doi-org.brum.beds.ac.uk/10.3390/telecom1020006 - 06 Jul 2020
Cited by 11 | Viewed by 3242
Abstract
In this paper, we describe a LoRa (from “Long Range”)-based, linear sensor network we have developed for transmitting location information of personnel and equipment in an underground mine. The system is intended to be used during emergencies when existing communications infrastructure has failed. [...] Read more.
In this paper, we describe a LoRa (from “Long Range”)-based, linear sensor network we have developed for transmitting location information of personnel and equipment in an underground mine. The system is intended to be used during emergencies when existing communications infrastructure has failed. Linear networks comprise a sequence of relays that forward data to a common destination, the headend. Relays forward location information transmitted from tags carried by personnel or equipment. Relays will usually be put in place as investigators or rescuers enter the mine. LoRa is used both by the tags to communicate to the relays and by the relays to forward messages to the headend. We have implemented and tested this system, and have carried out simulations and analyses to determine its scalability, reliability and fairness. The need for robustness and reliability has led us to use flooding rather than unicast communication. We also use message sequence numbers and time-to-live fields to prevent broadcast storms. Contention is managed using a simplified Carrier Sense Multiple Access (CSMA) scheme. We also address fairness. When the network is under load messages may be dropped by relays making messages generated more hops from the headend more likely to be dropped than messages nearer the headend. We explore the relationship between unfairness, traffic load and number of relays. We also observe that a network of larger numbers of lightly loaded relays performs more effectively than smaller numbers of heavily loaded relays. Full article
(This article belongs to the Special Issue Recent Advances in Smart and Pervasive Internet of Things)
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