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Advances in Wireless Communication Technologies
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Advances in Wireless Communication Technologies

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: 20 May 2024 | Viewed by 22267

Special Issue Editors

Prof. Dr. Paulo M. Mendes

E-Mail Website
Guest Editor
Dept. of Industrial Electronics, University of Minho, 4700-235 Braga, Portugal
Interests: microsystems; rf microelectronics; wireless sensor networks; biomedical devices; antennas; neural interfaces; wireless power
Special Issues, Collections and Topics in MDPI journals
Dr. Jose Cabral

E-Mail Website
Guest Editor
Dept. of Industrial Electronics, University of Minho, 4700-235 Braga, Portugal
Interests: broadband communications; IoT; underwater communications
Dr. Hugo Daniel da Costa Dinis

E-Mail Website
Guest Editor
CMEMS-UMinho, University of Minho, 4700-235 Braga, Portugal
Interests: RF and microwave devices; electromagnetic engineering

Special Issue Information

Dear Colleagues,

Wireless communications are unquestionably a cornerstone of modern society. Research in this field has been conducted for decades, and important advances are still being done nowadays. Advances in this field are constant, with upgrades being made on existing wireless standards (such as 4G, Bluetooth, Wi-Fi, Zigbee, LoRa,…) and with the constant push for new technologies (like 5G and now 6G). Despite the technological advances, the key success for wireless communications is its unquestionable enabling solution in countless key areas, such as environmental monitoring (oceans, forests, hydric resources, wildlife, agriculture, food, …), healthcare, aeronautics, space, surveillance, transportation, data sharing, communication, to mention just a few key applications.

Authors are invited to contribute to this special issue with their contributions to the advancement of wireless communication technologies, whether at the technological levels or as a novel application in any of the enumerated fields.

Prof. Dr. Paulo M. Mendes
Dr. Jose Cabral
Dr. Hugo Daniel da Costa Dinis
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. Applied Sciences 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 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

  • wireless communications
  • IoT
  • wireless sensor networks
  • environmental monitoring
  • healthcare monitoring
  • underwater communication
  • space
  • aeronautics
  • smart cities
  • autonomous vehicles

Published Papers (15 papers)

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Research

Jump to: Review

17 pages, 3016 KiB  
Article
Online Learning-Based Adaptive Device-Free Localization in Time-Varying Indoor Environment
by Jianqiang Xue, Xingcan Chen, Qingyun Chi and Wendong Xiao
Appl. Sci. 2024, 14(2), 643; https://doi.org/10.3390/app14020643 - 12 Jan 2024
Cited by 1 | Viewed by 710
Abstract
With the widespread use of WiFi devices and the availability of channel state information (CSI), CSI-based device-free localization (DFL) has attracted lots of attention. Fingerprint-based localization methods are the primary solutions for DFL, but they are faced with the fingerprint similarity problem due [...] Read more.
With the widespread use of WiFi devices and the availability of channel state information (CSI), CSI-based device-free localization (DFL) has attracted lots of attention. Fingerprint-based localization methods are the primary solutions for DFL, but they are faced with the fingerprint similarity problem due to the complex environment and low bandwidth of the commercial WiFi. Meanwhile, fingerprints may change unpredictably due to multipath WiFi signal propagation in time-varying environments. To tackle these problems, this paper proposes an adaptive online learning DFL method, which adaptively updates the localization model to ensure long-term accuracy and adaptability. Specifically, the CSI signals of the target located at different reference points are first collected and transformed to discriminable fingerprints using the weights of Multilayer Online Sequence Extreme Learning Machine (ML-OSELM). After that, an online learning DFL model is built to adapt to the changes of the environment. Experimental results in a time-varying indoor environment validate the adaptability of the proposed method against environmental changes and show that our method can achieve 10% improvement over other methods. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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12 pages, 4987 KiB  
Article
Fast Converging Gauss–Seidel Iterative Algorithm for Massive MIMO Systems
by Dong Shen, Li Chen and Hao Liang
Appl. Sci. 2023, 13(23), 12638; https://doi.org/10.3390/app132312638 - 24 Nov 2023
Viewed by 519
Abstract
Signal detection in massive MIMO systems faces many challenges. The minimum mean square error (MMSE) approach for massive multiple-input multiple-output (MIMO) communications offer near to optimal recognition but require inverting the high-dimensional matrix. To tackle this issue, a Gauss–Seidel (GS) detector based on [...] Read more.
Signal detection in massive MIMO systems faces many challenges. The minimum mean square error (MMSE) approach for massive multiple-input multiple-output (MIMO) communications offer near to optimal recognition but require inverting the high-dimensional matrix. To tackle this issue, a Gauss–Seidel (GS) detector based on conjugate gradient and Jacobi iteration (CJ) joint processing (CJGS) is presented. In order to accelerate algorithm convergence, the signal is first initialized using the optimal initialization regime among the three options. Second, the signal is processed via the CJ Joint Processor. The pre-processed result is then sent to the GS detector. According to simulation results, in channels with varying correlation values, the suggested iterative scheme’s BER is less than that of the GS and the improved iterative scheme based on GS. Furthermore, it can approach the BER performance of the MMSE detection algorithm with fewer iterations. The suggested technique has a computational complexity of O(U2), whereas the MMSE detection algorithm has a computational complexity of O(U3), where U is the number of users. For the same detection performance, the computational complexity of the proposed algorithm is an order of magnitude lower than that of MMSE. With fewer iterations, the proposed algorithm achieves a better balance between detection performance and computational complexity. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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19 pages, 15830 KiB  
Article
A Low-Cost Instrument for Multidimensional Characterization of Advanced Wireless Communication Technologies
by Rodrigo Gounella, Augusto Martins, Vinicius Pepino, Ben-Hur Viana Borges and João Paulo Carmo
Appl. Sci. 2023, 13(11), 6581; https://doi.org/10.3390/app13116581 - 29 May 2023
Viewed by 1480
Abstract
Exploring the potential of 3D printing in electromagnetic wave manipulation, this paper introduces a novel, cost-effective instrument for microwave metasurface characterization. Metasurfaces, designed to alter wave propagation, are promising tools for enhancing antenna efficiency in advanced telecommunication methods, such as 5G systems. However, [...] Read more.
Exploring the potential of 3D printing in electromagnetic wave manipulation, this paper introduces a novel, cost-effective instrument for microwave metasurface characterization. Metasurfaces, designed to alter wave propagation, are promising tools for enhancing antenna efficiency in advanced telecommunication methods, such as 5G systems. However, their complex profile characterization often poses significant challenges. Our proposed fully automated four-axis instrument, leveraging 3D printing capable of creating complex structures (such as metasurfaces), addresses these challenges by offering an efficient and precise solution. The instrument, costing approximately USD 1550, successfully characterized a metalens designed for modulating 30 GHz signals with a 20 cm focal distance, proving its utility. The 2D and 3D intensity distribution profiles and key parameters (including 8.05 dB gain, 11 cm 3 dB depth of focus, and 2.17 cm full width at half maximum) were extracted. Our measurements notably corresponded with the theoretical diffraction calculations, validating the instrument’s efficacy. This breakthrough significantly contributes to microwave metasurface characterization techniques which are vital for future millimeter-wave communication systems. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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17 pages, 2876 KiB  
Article
Automatic Clustering for Improved Radio Environment Maps in Distributed Applications
by Haithem Ben Chikha and Alaa Alaerjan
Appl. Sci. 2023, 13(10), 5902; https://doi.org/10.3390/app13105902 - 10 May 2023
Cited by 2 | Viewed by 1240
Abstract
Wireless communication greatly contributes to the evolution of new technologies, such as the Internet of Things (IoT) and edge computing. The new generation networks, including 5G and 6G, provide several connectivity advantages for multiple applications, such as smart health systems and smart cities. [...] Read more.
Wireless communication greatly contributes to the evolution of new technologies, such as the Internet of Things (IoT) and edge computing. The new generation networks, including 5G and 6G, provide several connectivity advantages for multiple applications, such as smart health systems and smart cities. Adopting wireless communication technologies in these applications is still challenging due to factors such as mobility and heterogeneity. Predicting accurate radio environment maps (REMs) is essential to facilitate connectivity and improve resource utilization. The construction of accurate REMs through the prediction of reference signal received power (RSRP) can be useful in densely distributed applications, such as smart cities. However, predicting an accurate RSRP in the applications can be complex due to intervention and mobility aspects. Given the fact that the propagation environments can be different in a specific area of interest, the estimation of a common path loss exponent for the entire area produces errors in the constructed REM. Hence, it is necessary to use automatic clustering to distinguish between different environments by grouping locations that exhibit similar propagation characteristics. This leads to better prediction of the propagation characteristics of other locations within the same cluster. Therefore, in this work, we propose using the Kriging technique, in conjunction with the automatic clustering approach, in order to improve the accuracy of RSRP prediction. In fact, we adopt K-means clustering (KMC) to enhance the path loss exponent estimation. We use a dataset to test the proposed model using a set of comparative studies. The results showed that the proposed approach provides significant RSRP prediction capabilities for constructing REM, with a gain of about 3.3 dB in terms of root mean square error compared to the case without clustering. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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17 pages, 1644 KiB  
Communication
Sum Rate Optimization Scheme of UAV-Assisted NOMA under Hardware Impairments
by Xiaoyu Wan, Xiongqing Yang, Zhengqiang Wang, Zifu Fan and Bin Duo
Appl. Sci. 2023, 13(5), 2971; https://doi.org/10.3390/app13052971 - 25 Feb 2023
Cited by 1 | Viewed by 1132
Abstract
In the unmanned aerial vehicle (UAV) assisted non-orthogonal multiple access (NOMA) networks, the practical hardware impairments (HIs) and resource allocation is still a challenging problem. Most existing research on resource allocation algorithms for UAV communication is considered with the ideal hardware condition. However, [...] Read more.
In the unmanned aerial vehicle (UAV) assisted non-orthogonal multiple access (NOMA) networks, the practical hardware impairments (HIs) and resource allocation is still a challenging problem. Most existing research on resource allocation algorithms for UAV communication is considered with the ideal hardware condition. However, the impact of HIs on system performance cannot be ignored, especially in the case of high bit rates. Considering the HIs, most studies are from the perspective of performance analysis. The resource allocation of UAV relay-assisted NOMA systems is investigated in this paper with HIs. We aim to maximize the sum rate by jointly optimizing the deployment of UAV and transmit power. To address this problem, we first transformed the mixed integer programming problem (MIPP) into a standard convex optimization problem based on successive convex approximation (SCA) technology. Then, we introduced the Lagrangian dual transformation and quadratic transform methods to solve the power allocation problem. Finally, we propose an effective iterative algorithm to achieve an approximate optimal solution. Numerical results demonstrate that the proposed algorithm achieved better performance in terms of the sum rate compared with other benchmark schemes. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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20 pages, 714 KiB  
Article
On the Performance of Coded Cooperative Communication with Multiple Energy-Harvesting Relays and Error-Prone Forwarding
by Slim Chaoui, Omar Alruwaili, Chafaa Hamrouni, Aarif Alutaybi and Afif Masmoudi
Appl. Sci. 2023, 13(5), 2910; https://doi.org/10.3390/app13052910 - 24 Feb 2023
Viewed by 933
Abstract
In this paper, we consider a coded cooperative communication network with multiple energy-harvesting (EH) relays. In order to adequately address the problem of error propagation due to the erroneous decoding at the relays, as in the case of conventional decode and forward (DF) [...] Read more.
In this paper, we consider a coded cooperative communication network with multiple energy-harvesting (EH) relays. In order to adequately address the problem of error propagation due to the erroneous decoding at the relays, as in the case of conventional decode and forward (DF) relaying protocol, we propose coded cooperative schemes with hard information relaying (HIR) and soft information relaying (SIR) strategies. The performance of the relayed communication with EH relay depends crucially on the channel decoding capability at the relay, channel gains at the source–relay and relay–destination links, and ultimately on the power-splitting ratio of the relay EH receiver. The exact closed-form expression for the outage probability performance of the coded cooperative scheme with HIR strategy and relay selection (CC-HIR-RS) is derived for both cases, namely for constant and optimal power-splitting ratios. Concerning the coded cooperative scheme with SIR strategy, a Rayleigh Gaussian log likelihood ratio-based model is used to describe the soft estimated symbols at the output of the relay soft encoder. Directives are provided to determine the model parameters, and, accordingly, the signal-to-noise ratio (SNR) of the equivalent one-hop relaying channel is derived. A closed-form expression for the outage probability performance of the proposed coded cooperative scheme with SIR and relay selection (CC-SIR-RS) is derived. In addition, a fuzzy logic-based power-splitting scheme in EH relay applying SIR is proposed. The fading coefficients of the source–relay and relay–destination links and distance between source and relay node are considered as input parameters of the fuzzy logic system to obtain an appropriate power-splitting ratio that leads to a quasi-optimal SNR of the equivalent end-to-end channel. Monte Carlo simulations are presented to demonstrate the validity of the analytical results, and a comparison between the performance of the CC-HIR-RS scheme with constant and optimized power-splitting ratios and that of the CC-SIR-RS scheme with constant and fuzzy logic-based power-splitting ratios is provided. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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13 pages, 1647 KiB  
Article
Power Allocation and User Grouping for NOMA Downlink Systems
by Jun Li, Tong Gao, Bo He, Wenjing Zheng and Fei Lin
Appl. Sci. 2023, 13(4), 2452; https://doi.org/10.3390/app13042452 - 14 Feb 2023
Cited by 5 | Viewed by 1958
Abstract
Non-orthogonal multiple access (NOMA) technology allows multiple users to use the same time-frequency resource to send signals, which can improve spectral efficiency and throughput. We study the problems of user grouping and power allocation in the downlink of a multi-carrier NOMA system. The [...] Read more.
Non-orthogonal multiple access (NOMA) technology allows multiple users to use the same time-frequency resource to send signals, which can improve spectral efficiency and throughput. We study the problems of user grouping and power allocation in the downlink of a multi-carrier NOMA system. The sum rate is the optimization goal. A step-by-step optimization is adopted. Users are grouped first and then power is allocated. For user grouping, the user grouping method based on the maximum channel gain difference is improved to prevent users with similar channel gains from being grouped together. For power allocation, the deep learning power allocation algorithm is used among subcarriers. Then, the closed-form expressions of power allocation between multiplexed users are derived according to the minimum transmission rate constraint. The simulation results show that compared with the fractional transmit power allocation method and fixed power allocation method, the deep learning power allocation method improves the system sum rate by about 2.2% and 19%, respectively. The power allocation methods we propose improve the system sum rate by about 10% compared to the fractional transmit power allocation method used among subcarriers and between multiplexed users. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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13 pages, 7025 KiB  
Article
Time Domain Analysis of NB-IoT Signals
by Andrea Barellini, Barbara Bracci, Gaetano Licitra and Alberto Maria Silvi
Appl. Sci. 2023, 13(4), 2242; https://doi.org/10.3390/app13042242 - 09 Feb 2023
Cited by 1 | Viewed by 1426
Abstract
The NB-IoT (NarrowBand-Internet of Things) radio technology is now widely implemented by mobile phone network operators to support the communication of IoT devices such as smart meters, insurance black boxes for cars, network connected waste bins, smart bicycles. In the present work, some [...] Read more.
The NB-IoT (NarrowBand-Internet of Things) radio technology is now widely implemented by mobile phone network operators to support the communication of IoT devices such as smart meters, insurance black boxes for cars, network connected waste bins, smart bicycles. In the present work, some LTE800 cells of different mobile phone network operators implementing the NB-IoT technology in the guard band mode have been investigated. The signals, consisting of a PRB (Physical Resource Block) 180 kHz wide, have been analyzed and characterized in the time domain by means of a narrow band instrumental chain equipped with a Rohde & Schwarz FSH8 spectrum analyzer. Time domain analysis allows us to identify, within the transmission frame, the position of the NB-IoT signaling channels such as the Narrowband Reference Signal (NRS), the primary (NPSS) and secondary (NSSS) synchronization signals and the broadcast channel (NPBCH), but, above all, to measure the power received during the transmission of the NRS. This value has been compared with that measured by the NB-IoT decoding module supplied on the same analyzer, in order to verify the equivalence of these measurement methods. This would allow use of a more diffuse and cheaper instrumentation rather than more expensive vector analyzers, currently required to assess electric fields due to the NB-IoT signals through the extrapolation techniques set by Italian CEI 211-7/E technical standard. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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20 pages, 6018 KiB  
Article
CPM-GFDM: A Novel Combination of Continuous Phase Modulation and Generalized Frequency Division Multiplexing for Wireless Communication
by Imran A. Tasadduq
Appl. Sci. 2023, 13(2), 854; https://doi.org/10.3390/app13020854 - 07 Jan 2023
Viewed by 1485
Abstract
In this paper, continuous phase modulation-generalized frequency division multiplexing (CPM-GFDM) is proposed. The performance of CPM-GFDM is evaluated over Gaussian and frequency selective fading channels. In the proposed technique, the mapper in the transmitter and the de-mapper in the receiver of traditional GFDM [...] Read more.
In this paper, continuous phase modulation-generalized frequency division multiplexing (CPM-GFDM) is proposed. The performance of CPM-GFDM is evaluated over Gaussian and frequency selective fading channels. In the proposed technique, the mapper in the transmitter and the de-mapper in the receiver of traditional GFDM are replaced by a CPM mapper and de-mapper, respectively. Using Monte-Carlo simulations, the bit error rate performance is evaluated for several rational values of the modulation index. We establish the superiority of CPM-GFDM over traditional GFDM using error performance plots through extensive simulations. We demonstrate that there are several values of the modulation index that give a performance superior to the conventional GFDM, with h=12,310,516,716 giving the best performance for additive white Gaussian noise (AWGN) channels, while for the frequency-selective channels the best performance is observed when h=310,516,716. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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19 pages, 2862 KiB  
Article
Mobile Anchor Route Scheduling with an Iterative Sensor Positioning Algorithm in Wireless Sensor Networks
by Shih-Chang Huang and Yi-Kai Wang
Appl. Sci. 2023, 13(1), 22; https://doi.org/10.3390/app13010022 - 20 Dec 2022
Cited by 1 | Viewed by 1208
Abstract
Locating deployed sensor nodes in wireless sensor networks is a crucial issue for general environmental monitoring applications. Most current positioning technologies use stationary anchors to compute the positions of sensor nodes. However, placing the static anchors in the monitoring area is not a [...] Read more.
Locating deployed sensor nodes in wireless sensor networks is a crucial issue for general environmental monitoring applications. Most current positioning technologies use stationary anchors to compute the positions of sensor nodes. However, placing the static anchors in the monitoring area is not a trivial job, especially in hazardous environments. Applying a mobile anchor is a good solution. This paper proposes an iterative sensor positioning (ISP) algorithm that uses the neighboring-positioned nodes to assist the mobile anchor in locating the unknown nodes. In addition, a mobile anchor route scheduling method, named MARS, is also proposed to shorten the traveling distance of the mobile anchor. MARS uses a projection mechanism and the ISP algorithm to reduce the traveling distance. Simulation results indicate that MARS can reduce the traveling distance of the mobile anchor by about 21–49% compared with the SCAN method. In the unfavorable scenario of the projection mechanism, MARS still provides the mobile anchor with a traveling distance that is 34% less than the SCAN method. The mobile anchor, when applying the MARS method, is able to locate all unknown nodes in only 45% to 70% of the traveling distance required by the one using the SCAN method in the scenario favorable to the ISP algorithm, while still reducing the traveling distance by 15% to 21% in the scenario unfavorable to the ISP algorithm. In the non-ideal signal scenario, the positioning size of the positioning area of the ISP algorithm when using the MARS method is about 53% to 74% less than when using the Triangulation algorithm. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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21 pages, 4987 KiB  
Article
Joint Optimization Algorithm for Small Base Station States Control and User Association in Wireless Caching Networks
by Weipeng Wang, Jihong Zhao, Hua Qu and Huijun Dai
Appl. Sci. 2022, 12(23), 12372; https://doi.org/10.3390/app122312372 - 02 Dec 2022
Viewed by 1015
Abstract
The energy consumption management of small base stations (SBSs) in wireless caching networks with dense deployment of SBSs is an urgent problem to be solved. This paper jointly optimizes the SBS state control and user association problems in caching networks to reduce network [...] Read more.
The energy consumption management of small base stations (SBSs) in wireless caching networks with dense deployment of SBSs is an urgent problem to be solved. This paper jointly optimizes the SBS state control and user association problems in caching networks to reduce network energy consumption while taking into account the average service latency of the network to ensure user experience. First, a new definition of three-state SBSs in caching networks is proposed based on their ability to keep content cache updated. Then, a relaxed threshold setting method is designed and the SBS traffic prediction is used to obtain the initial state information of SBSs in the next period. In order to eliminate the impact on the accessing users when the switched-off base station (BS) wakes up, a SBS state asynchronous switching mechanism is proposed to ensure that the users who switch to the waking SBS can carry out communication services normally, and a user association strategy is constructed with the SBS load as the optimization target. Finally, a joint optimization model of user association and SBS state control (SSC-UA) is constructed to admit and correct the initial state of SBSs to maximize the system gain and obtain the final state strategy for each SBS in the next period. The simulation results show that the proposed SSC-UA algorithm can effectively improve the energy efficiency and reduce the network service delay at the same time. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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18 pages, 498 KiB  
Article
Energy-Efficient Resource Allocation for Downlink Non-Orthogonal Multiple Access Systems
by Yue Cui, Peng Liu, Yalei Zhou and Wenli Duan
Appl. Sci. 2022, 12(19), 9740; https://doi.org/10.3390/app12199740 - 27 Sep 2022
Cited by 4 | Viewed by 1539
Abstract
With the rapid popularization of intelligent terminals and the explosive growth of wireless communication service demand, future mobile communication technology will face many challenges. Non-orthogonal multiple access (NOMA) technology for 5G can provide many connections and effectively improve the frequency spectrum and energy [...] Read more.
With the rapid popularization of intelligent terminals and the explosive growth of wireless communication service demand, future mobile communication technology will face many challenges. Non-orthogonal multiple access (NOMA) technology for 5G can provide many connections and effectively improve the frequency spectrum and energy efficiency compared to traditional orthogonal multiple access technologies. Therefore, in recent years, NOMA technology has become one of the research hotspots of numerous scholars. However, the resource allocation problem in the NOMA system, as a high-dimensional nonlinear programming problem, has not been well studied. In addition, the particle swarm optimization algorithm can also effectively find the optimal solution for complex and constrained problems. Still, at the same time, it is easy to fall into local optimal defects. In this context, we decouple the high-dimensional nonlinear programming problem to maximize system energy efficiency into sub-problems: subchannel and power allocation. Firstly, a low-complexity greedy algorithm based on the principle of worst-case subchannel priority matching is proposed to solve the subchannel assignment problem. In addition, we further apply the modified particle swarm optimization algorithm to allocate power to the NOMA downlink system, aiming to improve the energy efficiency of the communication system as much as possible under the premise of ensuring the quality of service (QoS). Simulation results show that our proposed scheme has low complexity and can significantly improve the energy efficiency of the NOMA system and achieve better user fairness. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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10 pages, 3555 KiB  
Article
A Novel Approach for Micro-Antenna Fabrication on ZrO2 Substrate Assisted by Laser Printing for Smart Implants
by C. G. Moura, H. Dinis, O. Carvalho, P. M. Mendes, R. M. Nascimento and F. S. Silva
Appl. Sci. 2022, 12(18), 9333; https://doi.org/10.3390/app12189333 - 17 Sep 2022
Cited by 1 | Viewed by 1687
Abstract
The use of Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) in medicine has rapidly expanded over the past decade, driven by its advantageous properties, showing potential to overcome titanium alloy in implant fabrication. The release of metal ions and the aesthetic problems of titanium alloy [...] Read more.
The use of Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) in medicine has rapidly expanded over the past decade, driven by its advantageous properties, showing potential to overcome titanium alloy in implant fabrication. The release of metal ions and the aesthetic problems of titanium alloy implants are the main reasons for this trend. In addition to meeting expectations regarding its properties, an implant must possess intrinsic capacities such as auto-diagnostic and auto-treatment. Thus, based on the concept of smart implants, this work proposes a hybrid approach for printing a part of the communication system of a zirconia implant by resorting to laser technology, aiming to endow the implant with intrinsic capacities. Therefore, the antenna was designed and then printed on the zirconia surface. The laser was applied as a versatile tool, whether for preparing the surface of the material in a subtractive way, by creating the micro-cavity, or for printing the silver-based antenna in an additive way through laser technology. The silver powder was used as the conductor material of the antenna. The results revealed that the antenna is capable of communicating from inside the body with the outside world without needing to have an exterior antenna attached to the skin. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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16 pages, 1440 KiB  
Article
CoMP-Aware BBU Placements for 5G Radio Access Networks over Optical Aggregation Networks
by Ahmed M. Awad, Mohamed Shehata, Safa M. Gasser and Hesham EL-Badawy
Appl. Sci. 2022, 12(17), 8586; https://doi.org/10.3390/app12178586 - 27 Aug 2022
Cited by 3 | Viewed by 1319
Abstract
The huge traffic demand envisioned in 5G requires radical changes in mobile network architecture. A Centralized Radio Access Network (C-RAN) was introduced as a novel mobile network architecture, designed to effectively support the challenging requirements of future 5G networks. Coordinated Multi-point (CoMP) is [...] Read more.
The huge traffic demand envisioned in 5G requires radical changes in mobile network architecture. A Centralized Radio Access Network (C-RAN) was introduced as a novel mobile network architecture, designed to effectively support the challenging requirements of future 5G networks. Coordinated Multi-point (CoMP) is one of the technologies aiming to increase user traffic by transforming inter-cell interference into useful signals to maximize cell-edge users throughput. Intra-CoMP means that cooperating RRHs are assigned to the same Base Band Unit (BBU). On the other hand, in inter-CoMP, the cooperating RRHs are assigned to different BBUs, which introduce overhead signalling over an X2 interface. This paper proposes a model for BBU placement in C-RAN deployment over a 5G optical aggregation network. The model aims to minimize the number of users undergoing inter-CoMP, therefore reducing X2 signalling overhead. First, we solve the BBU placement problem using Integer Linear Programming (ILP), which minimizes the number of BBUs and the number of used links. Second, given the output of the ILP model (i.e., BBU locations and routes), we propose a heuristic algorithm to reconfigure the BBUs (i.e., the assignment of the RRHs to their corresponding BBUs), which aims at minimizing the number of users undergoing inter-CoMP. The proposed heuristic algorithm considers minimizing end-to-end delay, the number of used wavelengths, and maximizing multiplexing gain. The results show that up to 97% of inter-CoMP users migrated to intra-CoMP users. This results in a decrease in the X2 traffic, which is mainly used for the coordination between the BBUs. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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Review

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12 pages, 1132 KiB  
Review
The Challenge of Long-Distance Over-the-Air Wireless Links in the Ocean: A Survey on Water-to-Water and Water-to-Land MIoT Communication
by Hugo Dinis, João Rocha, Tiago Matos, Luís M. Gonçalves and Marcos Martins
Appl. Sci. 2022, 12(13), 6439; https://doi.org/10.3390/app12136439 - 24 Jun 2022
Cited by 4 | Viewed by 2796
Abstract
Robust wireless communication networks are a cornerstone of the modern world, allowing data to be transferred quickly and reliably. Establishing such a network at sea, a Maritime Internet of Things (MIoT), would enhance services related to safety and security at sea, environmental protection, [...] Read more.
Robust wireless communication networks are a cornerstone of the modern world, allowing data to be transferred quickly and reliably. Establishing such a network at sea, a Maritime Internet of Things (MIoT), would enhance services related to safety and security at sea, environmental protection, and research. However, given the remote and harsh nature of the sea, installing robust wireless communication networks with adequate data rates and low cost is a difficult endeavor. This paper reviews recent MIoT systems developed and deployed by researchers and engineers over the past few years. It contains an analysis of short-range and long-range over-the-air radio-frequency wireless communication protocols and the synergy between these two in the pursuit of an MIoT. The goal of this paper is to serve as a go-to guide for engineers and researchers that need to implement a wireless sensor network at sea. The selection criterion for the papers included in this review was that the implemented wireless communication networks were tested in a real-world scenario. Full article
(This article belongs to the Special Issue Advances in Wireless Communication Technologies)
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