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Electronics, Volume 10, Issue 14 (July-2 2021) – 138 articles

Cover Story (view full-size image): To increase the effectiveness of virtual job training for people with intellectual disabilities in training situations in which they may experience difficulty and become unable to proceed further, the contents of the training program need to automatically identify such moments and provide support. To identify the moment of intervention, we conducted an experiment to collect the eye tracking data of people with intellectual disabilities while performing virtual-reality-based barista training and measured eye scanning patterns. We found that the information about the types of fixated objects did not help to identify any difference, but the information about eye transition was useful in identifying the difference. View this paper
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Article
Building Complete Heterogeneous Systems-on-Chip in C: From Hardware Accelerators to CPUs
Electronics 2021, 10(14), 1746; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141746 - 20 Jul 2021
Viewed by 390
Abstract
High-Level Synthesis (HLS) dramatically accelerates the design and verification of individual components within larger VLSI systems. With most complex Integrated Circuits (ICs) being now heterogeneous Systems-on-Chip (SoCs), HLS has been traditionally used to design the dedicated hardware accelerators such as encryption cores and [...] Read more.
High-Level Synthesis (HLS) dramatically accelerates the design and verification of individual components within larger VLSI systems. With most complex Integrated Circuits (ICs) being now heterogeneous Systems-on-Chip (SoCs), HLS has been traditionally used to design the dedicated hardware accelerators such as encryption cores and Digital Signal Processing (DSP) image processing accelerators. Unfortunately, HLS is a single process (component) synthesis method. Thus, the integration of these accelerators has to be performed at the RT level (Verilog or VHDL). This implies that the system-level verification needs to be performed at lower levels of abstraction, which significantly diminishes the benefits of using HLS. To address this, this work presents a methodology to generate entire heterogeneous SoCs in C. This work introduces two main contributions that enable this: first, an automatic bus generator that generates a synthesizable behavioral description of standard on-chip buses and, second, a library of synthesizable bus interfaces that allow any component in the system to send or receive data through the bus. Moreover, this work investigates the generation of processors and interfaces (peripherals) at the behavioral level as these are important parts of any SoCs, but have long been thought not to be efficiently synthesizable using HLS. Generating complete SoCs in C has significant advantages over traditional approaches. First, it enables the generation of fast cycle-accurate simulation models of the entire SoC, making the verification faster and easier. Second, it allows completely isolating the bus implementation details from the developers’ view, allowing the change between bus protocols with only minor changes in the designers’ code. Thirdly, it allows generating different SoC variants quickly by only changing the HLS synthesis options. Experimental results highlight these benefits. Full article
(This article belongs to the Special Issue Advances in System-on-Chip Design)
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Article
Experimental and Simulation-Based Performance Analysis of a Computed Torque Control (CTC) Method Running on a Double Rotor Aeromechanical Testbed
Electronics 2021, 10(14), 1745; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141745 - 20 Jul 2021
Cited by 1 | Viewed by 368
Abstract
Concept of closed loop control appears in many fields of engineering sciences, where the output quantity of some physical system must be forced to follow some prescribed function over time, e.g., when a robotic arm endpoint must track a desired trajectory or path [...] Read more.
Concept of closed loop control appears in many fields of engineering sciences, where the output quantity of some physical system must be forced to follow some prescribed function over time, e.g., when a robotic arm endpoint must track a desired trajectory or path given as timed series of spatial coordinates. The classic approach for solving this kind of problem involves a PID compensation block, and the necessary input signal for keeping the controlled process in the vicinity of the desired trajectory is calculated as the weighted sum of momentary deviation, deviation integral, and deviation derivative relative to the reference path. However, despite the obvious advantages, practical usability, and simplicity of the PID controllers, their performance is limited when they are utilized for controlling nonlinear systems. Even with linear systems, their proper operation requires an accurate system model and precise tuning process for finding the best weight values for the proportional, integral, and derivative effects, and the planned closed loop behavior might change significantly as the parameters of the controlled plant change over time. In this article, a computed torque-based controller is presented, which has only one adjustable parameter ensuring precise trajectory tracking even with significantly alternated model constants. The practical usability of the offered algorithm is evaluated and verified by simulations and experiments performed on a simple mechanical bi-rotor testbed playing the role of controlled plant. Full article
(This article belongs to the Special Issue Computational Cybernetics)
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Review
Secure Watermarking Schemes and Their Approaches in the IoT Technology: An Overview
Electronics 2021, 10(14), 1744; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141744 - 20 Jul 2021
Viewed by 431
Abstract
Information security is considered one of the most important issues in various infrastructures related to the field of data communication where most of the modern studies focus on finding effective and low-weight secure approaches. Digital watermarking is a trend in security techniques that [...] Read more.
Information security is considered one of the most important issues in various infrastructures related to the field of data communication where most of the modern studies focus on finding effective and low-weight secure approaches. Digital watermarking is a trend in security techniques that hides data by using data embedding and data extraction processes. Watermarking technology is integrated into different frames without adding an overheard as in the conventional encryption. Therefore, it is efficient to be used in data encryption for applications that run over limited resources such as the Internet of Things (IoT). In this paper, different digital watermarking algorithms and approaches are presented. Additionally, watermarking requirements and challenges are illustrated in detail. Moreover, the common architecture of the watermarking system is described. Furthermore, IoT technology and its challenges are highlighted. Finally, the paper provides the motivations, objectives and applications of the recent secure watermarking techniques in IoT and summarises them into one table. In addition, the paper highlights the potential to apply the modified watermark algorithms to secure IoT networks. Full article
(This article belongs to the Special Issue Intelligence/Security Embedded IoT Systems)
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Article
A 33 MHz Fast-Locking PLL with Programmable VCO and Automatic Band Selection for Clock Generator Application
Electronics 2021, 10(14), 1743; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141743 - 20 Jul 2021
Cited by 1 | Viewed by 435
Abstract
This paper presents a prototype of an auto-ranging phase-locked loop (PLL) with low jitter noise over a wide operating frequency range using the multiband programmable voltage-controlled oscillator (VCO) gain stage with automatic band selection. We successfully reduce the VCO gain (Kvco) and retain [...] Read more.
This paper presents a prototype of an auto-ranging phase-locked loop (PLL) with low jitter noise over a wide operating frequency range using the multiband programmable voltage-controlled oscillator (VCO) gain stage with automatic band selection. We successfully reduce the VCO gain (Kvco) and retain the desired frequency band. The proposed PLL comprises a prescaler, phase frequency detector (PFD), charge pump (CP), programmable VCO and automatic band selection circuit. The PLL prototype with all subblocks was implemented using the TSMC 0.18 μm 1P6M process. Contrary to conventional PLL architectures, the proposed architecture incorporates a real-time check and automatic band selection circuit in the secondary loop. A high-performance dual-loop PLL wide tuning range was realized using an ASIC digital control circuit. A suitable way to maintain the Kvco low is to use multiple discrete frequency bands to accommodate the required frequency range. To maintain a low Kvco and fast locking, the automatic frequency band selection circuit also has two indigenous, most probable voltage levels. The proposed architecture provides the flexibility of not only band hopping but also band twisting to obtain an optimized Kvco for the desired output range, with the minimum jitter and spurs. The proposed programmable VCO was designed using a voltage-to-current-converter circuit and current DAC followed by a four-stage differential ring oscillator with a cross-coupled pair. The VCO frequency output range is 150–400 MHz, while the input frequency is 25 MHz. A sequential phase detection loop with a negligible dead zone was designed to adjust fine phase errors between the reference and feedback clocks. All circuit blocks of the proposed PLL were simulated using the EDA tool HSPICE and layout generation by Laker. The simulation and measured results of the proposed PLL show high linearity, with a dead zone of less than 10 pV. The differential VCO was used to improve the linearity and phase noise of the PLL. The chip measured results show rms jitter of 19.10 ps. The PLL prototype also has an additional safety feature of a power down mode. The automatic band selection PLL has good immunity for possible frequency drifting due to temperature, process and supply voltage variations. The proposed PLL is designed for −40 to +85 °C, a wide temperature range. Full article
(This article belongs to the Special Issue Design of Mixed Analog/Digital Circuits)
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Article
A Novel Multifunctional Negative Group Delay Circuit for Realizing Band-Pass, High-Pass and Low-Pass
Electronics 2021, 10(14), 1742; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141742 - 20 Jul 2021
Viewed by 313
Abstract
A novel multifunctional negative group delay circuit is proposed. The circuit can realize three different negative group delay functions, including band-pass, high-pass and low-pass, which meet different conditions with capacitance, inductance and resistance. Analytical design equations are provided. The effects of different element [...] Read more.
A novel multifunctional negative group delay circuit is proposed. The circuit can realize three different negative group delay functions, including band-pass, high-pass and low-pass, which meet different conditions with capacitance, inductance and resistance. Analytical design equations are provided. The effects of different element values on the bandwidth, cut-off frequency and the minimum negative group delay of the circuit are analyzed. According to this design method, the negative group delay circuit is designed and fabricated. Simulation and measurement results are in agreement. It has good negative group delay characteristics. The feasibility of the design method is verified. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Article
Design of a 20 T Class REBCO Insert in a 15 T Low Temperature Superconducting Magnet
Electronics 2021, 10(14), 1741; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141741 - 20 Jul 2021
Viewed by 351
Abstract
A 20 T REBCO insert magnet has been designed considering a 15 T/150 mm background field generated by an LTS magnet. A two-nested-coil structure was chosen. The target of this project is to generate a 20 T/80 mm user field by inserting the [...] Read more.
A 20 T REBCO insert magnet has been designed considering a 15 T/150 mm background field generated by an LTS magnet. A two-nested-coil structure was chosen. The target of this project is to generate a 20 T/80 mm user field by inserting the outer MI-REBCO coil (Coil 2) first, then try to reach 35 T by inserting the inner NI-REBCO test coil (Coil 1). Coil 2 will be wound by copper packed, 185-μm thick REBCO tapes co-wound with 50-μm thick Hastelloy tapes. Coil 1 will be no-insulated wound by 65-μm thick REBCO tapes. Two mechanical models were built to estimate the stress distribution inside the HTS coils during operation. The influence of the screening current distribution on stress was discussed. The unbalanced force caused by the coil misalignment was also simulated. The 20 T HTS insert magnet is planned to be built and tested in 2021. The progress of coil winding and preliminary test results at 77 K were presented. Full article
(This article belongs to the Section Quantum Electronics)
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Article
GaborPDNet: Gabor Transformation and Deep Neural Network for Parkinson’s Disease Detection Using EEG Signals
Electronics 2021, 10(14), 1740; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141740 - 20 Jul 2021
Cited by 1 | Viewed by 480
Abstract
Parkinson’s disease (PD) is globally the most common neurodegenerative movement disorder. It is characterized by a loss of dopaminergic neurons in the substantia nigra of the brain. However, current methods to diagnose PD on the basis of clinical features of Parkinsonism may lead [...] Read more.
Parkinson’s disease (PD) is globally the most common neurodegenerative movement disorder. It is characterized by a loss of dopaminergic neurons in the substantia nigra of the brain. However, current methods to diagnose PD on the basis of clinical features of Parkinsonism may lead to misdiagnoses. Hence, noninvasive methods such as electroencephalographic (EEG) recordings of PD patients can be an alternative biomarker. In this study, a deep-learning model is proposed for automated PD diagnosis. EEG recordings of 16 healthy controls and 15 PD patients were used for analysis. Using Gabor transform, EEG recordings were converted into spectrograms, which were used to train the proposed two-dimensional convolutional neural network (2D-CNN) model. As a result, the proposed model achieved high classification accuracy of 99.46% (±0.73) for 3-class classification (healthy controls, and PD patients with and without medication) using tenfold cross-validation. This indicates the potential of proposed model to simultaneously automatically detect PD patients and their medication status. The proposed model is ready to be validated with a larger database before implementation as a computer-aided diagnostic (CAD) tool for clinical-decision support. Full article
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Article
Towards Hybrid Multimodal Manual and Non-Manual Arabic Sign Language Recognition: mArSL Database and Pilot Study
Electronics 2021, 10(14), 1739; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141739 - 20 Jul 2021
Viewed by 347
Abstract
Sign languages are the main visual communication medium between hard-hearing people and their societies. Similar to spoken languages, they are not universal and vary from region to region, but they are relatively under-resourced. Arabic sign language (ArSL) is one of these languages that [...] Read more.
Sign languages are the main visual communication medium between hard-hearing people and their societies. Similar to spoken languages, they are not universal and vary from region to region, but they are relatively under-resourced. Arabic sign language (ArSL) is one of these languages that has attracted increasing attention in the research community. However, most of the existing and available works on sign language recognition systems focus on manual gestures, ignoring other non-manual information needed for other language signals such as facial expressions. One of the main challenges of not considering these modalities is the lack of suitable datasets. In this paper, we propose a new multi-modality ArSL dataset that integrates various types of modalities. It consists of 6748 video samples of fifty signs performed by four signers and collected using Kinect V2 sensors. This dataset will be freely available for researchers to develop and benchmark their techniques for further advancement of the field. In addition, we evaluated the fusion of spatial and temporal features of different modalities, manual and non-manual, for sign language recognition using the state-of-the-art deep learning techniques. This fusion boosted the accuracy of the recognition system at the signer-independent mode by 3.6% compared with manual gestures. Full article
(This article belongs to the Special Issue Deep Learning for Computer Vision and Pattern Recognition)
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Article
Dirt Loss Estimator for Photovoltaic Modules Using Model Predictive Control
Electronics 2021, 10(14), 1738; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141738 - 19 Jul 2021
Viewed by 458
Abstract
The central problem tackled in this article is the susceptibility of the solar modules to dirt that culminates in losses in energy generation or even physical damage. In this context, a solution is presented to enable the estimates of dirt losses in photovoltaic [...] Read more.
The central problem tackled in this article is the susceptibility of the solar modules to dirt that culminates in losses in energy generation or even physical damage. In this context, a solution is presented to enable the estimates of dirt losses in photovoltaic generation units. The proposed solution is based on the mathematical modeling of the solar cells and predictive modeling concepts. A device was designed and developed to acquire data from the photovoltaic unit; process them based on a predictive model, and send loss estimates in the generation unit to a web server to help in decision-making support. The results demonstrated the real applicability of the system to estimate losses due to dirt or electrical mismatches in photovoltaic plants. Full article
(This article belongs to the Special Issue Predictive and Learning Control in Engineering Applications)
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Article
The Design of Preventive Automated Driving Systems Based on Convolutional Neural Network
Electronics 2021, 10(14), 1737; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141737 - 19 Jul 2021
Viewed by 395
Abstract
As automated vehicles have been considered one of the important trends in intelligent transportation systems, various research is being conducted to enhance their safety. In particular, the importance of technologies for the design of preventive automated driving systems, such as detection of surrounding [...] Read more.
As automated vehicles have been considered one of the important trends in intelligent transportation systems, various research is being conducted to enhance their safety. In particular, the importance of technologies for the design of preventive automated driving systems, such as detection of surrounding objects and estimation of distance between vehicles. Object detection is mainly performed through cameras and LiDAR, but due to the cost and limits of LiDAR’s recognition distance, the need to improve Camera recognition technique, which is relatively convenient for commercialization, is increasing. This study learned convolutional neural network (CNN)-based faster regions with CNN (Faster R-CNN) and You Only Look Once (YOLO) V2 to improve the recognition techniques of vehicle-mounted monocular cameras for the design of preventive automated driving systems, recognizing surrounding vehicles in black box highway driving videos and estimating distances from surrounding vehicles through more suitable models for automated driving systems. Moreover, we learned the PASCAL visual object classes (VOC) dataset for model comparison. Faster R-CNN showed similar accuracy, with a mean average precision (mAP) of 76.4 to YOLO with a mAP of 78.6, but with a Frame Per Second (FPS) of 5, showing slower processing speed than YOLO V2 with an FPS of 40, and a Faster R-CNN, which we had difficulty detecting. As a result, YOLO V2, which shows better performance in accuracy and processing speed, was determined to be a more suitable model for automated driving systems, further progressing in estimating the distance between vehicles. For distance estimation, we conducted coordinate value conversion through camera calibration and perspective transform, set the threshold to 0.7, and performed object detection and distance estimation, showing more than 80% accuracy for near-distance vehicles. Through this study, it is believed that it will be able to help prevent accidents in automated vehicles, and it is expected that additional research will provide various accident prevention alternatives such as calculating and securing appropriate safety distances, depending on the vehicle types. Full article
(This article belongs to the Special Issue AI-Based Transportation Planning and Operation, Volume II)
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Article
High Power Density, High-Voltage Parallel Resonant Converter Using Parasitic Capacitance on the Secondary Side of a Transformer
Electronics 2021, 10(14), 1736; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141736 - 19 Jul 2021
Cited by 1 | Viewed by 351
Abstract
High-voltage DC power supplies are used in several applications, including X-ray, plasma, electrostatic precipitator, and capacitor charging. However, such a high-voltage power supply has problems, such as a decrease in reliability, owing to an increase in output ripple voltage, and a decrease in [...] Read more.
High-voltage DC power supplies are used in several applications, including X-ray, plasma, electrostatic precipitator, and capacitor charging. However, such a high-voltage power supply has problems, such as a decrease in reliability, owing to an increase in output ripple voltage, and a decrease in power density, owing to an increase in volume. Therefore, this study proposes a method for improving the power density of a parallel resonant converter using the parasitic capacitor of the secondary side of the transformer. Due to the fact that high-voltage power supplies have many turns on the secondary side, a significant number of parasitic capacitors are generated. In addition, in the case of a parallel resonant converter, because the transformer and the primary resonant capacitor are connected in parallel, the parasitic capacitor component generated on the secondary side of the transformer can be equalized and used. A parallel cap-less resonant converter structure developed using the parasitic components of such transformers is proposed. Primary side and secondary side equivalent model analyses are conducted in order to derive new equations and gain waveforms. Finally, the validity of the proposed structure is verified experimentally. Full article
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Article
Adaptive Data Length Method for GPS Signal Acquisition in Weak to Strong Fading Conditions
Electronics 2021, 10(14), 1735; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141735 - 19 Jul 2021
Viewed by 328
Abstract
Satellite-based navigation is an essential part of all the technology-dependent applications, such as road transport, cell phones, the medical field, aviation or the shipping industry, etc. The performance of the navigation systems depends upon how quickly they can acquire and process the received [...] Read more.
Satellite-based navigation is an essential part of all the technology-dependent applications, such as road transport, cell phones, the medical field, aviation or the shipping industry, etc. The performance of the navigation systems depends upon how quickly they can acquire and process the received signals for positioning solutions. However, in dense urban or indoor environments, signal acquisition can be a challenging task due to fading as a result of multipath and/or interference. This paper presents post-processing acquisition results on Global Positioning System (GPS) signals to study the relationship between data lengths used for signal acquisition and the achieved signal power using a Fast Fourier Transform (FFT)-based circular correlation method. Based on this study, the detection performance of the FFT-based method has also been analyzed by intentionally degrading the signal power levels. A new Adaptive Data length (ADL) method for acquisition has been proposed in this paper, which can be used for speeding up the acquisition process and uses adaptive data lengths rather than fixed data lengths. The ADL method works by estimating the threshold level based on the noise present in the signal and then comparing it with the signal power levels. Less difference between the threshold level and signal power level means less data length will be used while more difference means that more data length will be used for acquisition. The proposed algorithm can be used in commercially available receivers for adopting to an adaptive acquisition process for increased efficiency. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Article
Single-Shunt Three-Phase Current Measurement for a Three-Level Inverter Using a Modified Space-Vector Modulation
Electronics 2021, 10(14), 1734; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141734 - 19 Jul 2021
Viewed by 353
Abstract
This article presents a single-shunt measurement of a three-level inverter using a modified space-vector modulation to reconstruct the three-phase load current. The proposed method was implemented on a digital signal processor (DSP), and the algorithm was verified in the laboratory experiment. Through the [...] Read more.
This article presents a single-shunt measurement of a three-level inverter using a modified space-vector modulation to reconstruct the three-phase load current. The proposed method was implemented on a digital signal processor (DSP), and the algorithm was verified in the laboratory experiment. Through the work, it was proven that the single-shunt three-phase current measurement could be performed using the space-vector modulation for three-level inverters in an analogous way to ordinary three-phase inverters. Three-phase current reconstruction for ordinary three-phase inverters was performed using the ordinary space-vector modulation with eight vectors, but for three-level inverters, 21 vectors were available. When the inverter was working on the edges between two vectors, the modulation disturbances appeared as current spikes. This problem was solved using the modified SVM performed by shifting the SVM signals. Carefully designed signal shifting (vector injection) demonstrated an excellent reconstruction of the three-phase load currents that were single-shunt measured. Full article
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Article
An Extended Semantic Interoperability Model for Distributed Electronic Health Record Based on Fuzzy Ontology Semantics
Electronics 2021, 10(14), 1733; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141733 - 19 Jul 2021
Viewed by 443
Abstract
Semantic interoperability of distributed electronic health record (EHR) systems is a crucial problem for querying EHR and machine learning projects. The main contribution of this paper is to propose and implement a fuzzy ontology-based semantic interoperability framework for distributed EHR systems. First, a [...] Read more.
Semantic interoperability of distributed electronic health record (EHR) systems is a crucial problem for querying EHR and machine learning projects. The main contribution of this paper is to propose and implement a fuzzy ontology-based semantic interoperability framework for distributed EHR systems. First, a separate standard ontology is created for each input source. Second, a unified ontology is created that merges the previously created ontologies. However, this crisp ontology is not able to answer vague or uncertain queries. We thirdly extend the integrated crisp ontology into a fuzzy ontology by using a standard methodology and fuzzy logic to handle this limitation. The used dataset includes identified data of 100 patients. The resulting fuzzy ontology includes 27 class, 58 properties, 43 fuzzy data types, 451 instances, 8376 axioms, 5232 logical axioms, 1216 declarative axioms, 113 annotation axioms, and 3204 data property assertions. The resulting ontology is tested using real data from the MIMIC-III intensive care unit dataset and real archetypes from openEHR. This fuzzy ontology-based system helps physicians accurately query any required data about patients from distributed locations using near-natural language queries. Domain specialists validated the accuracy and correctness of the obtained results. Full article
(This article belongs to the Special Issue Intelligent Systems for Healthcare and Biomedical Engineering)
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Review
Privacy Preservation in Resource-Constrained IoT Devices Using Blockchain—A Survey
Electronics 2021, 10(14), 1732; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141732 - 19 Jul 2021
Viewed by 530
Abstract
With opportunities brought by Internet of Things (IoT), it is quite a challenge to assure privacy preservation when a huge number of resource-constrained distributed devices is involved. Blockchain has become popular for its benefits, including decentralization, persistence, immutability, auditability and consensus. With the [...] Read more.
With opportunities brought by Internet of Things (IoT), it is quite a challenge to assure privacy preservation when a huge number of resource-constrained distributed devices is involved. Blockchain has become popular for its benefits, including decentralization, persistence, immutability, auditability and consensus. With the implementation of blockchain in IoT, the benefits provided by blockchain can be derived in order to make IoT more efficient and maintain trust. In this paper, we discuss some applications of IoT in different fields and privacy-related issues faced by IoT in resource-constrained devices. We discuss some applications of blockchain in vast majority of areas, and the opportunities it brings to resolve IoT privacy limitations. We, then, survey different researches based on the implementation of blockchain in IoT. The goal of this paper is to survey recent researches based on the implementation of blockchain in IoT for privacy preservation. After analyzing the recent solutions, we see that the blockchain is an optimal way for preventing identity disclosure, monitoring, and providing tracking in IoT. Full article
(This article belongs to the Special Issue Security and Privacy for IoT and Multimedia Services)
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Article
Normalized Partial Scattering Cross Section for Performance Evaluation of Low-Observability Scattering Structures
Electronics 2021, 10(14), 1731; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141731 - 19 Jul 2021
Viewed by 295
Abstract
The development of diffusion metasurfaces created new opportunities to elevate the stealthiness of combat aircraft. Despite the potential significance of metasurfaces, their rigorous design methodologies are still lacking, especially in the context of meticulous control over the scattering of electromagnetic (EM) waves through [...] Read more.
The development of diffusion metasurfaces created new opportunities to elevate the stealthiness of combat aircraft. Despite the potential significance of metasurfaces, their rigorous design methodologies are still lacking, especially in the context of meticulous control over the scattering of electromagnetic (EM) waves through geometry parameter tuning. Another practical issue is insufficiency of the existing performance metrics, specifically, monostatic and bistatic evaluation of the reflectivity, especially at the design stage of metasurfaces. Both provide limited insight into the RCS reduction properties, with the latter being dependent on the selection of the planes over which the evaluation takes place. This paper introduces a novel performance metric for evaluating scattering characteristics of a metasurface, referred to as Normalized Partial Scattering Cross Section (NPSCS). The metric involves integration of the scattered energy over a specific solid angle, which allows for a comprehensive assessment of the structure performance in a format largely independent of the particular arrangement of the scattering lobes. We demonstrate the utility of the introduced metric using two specific metasurface architectures. In particular, we show that the integral-based metric can be used to discriminate between the various surface configurations (e.g., checkerboard versus random), which cannot be conclusively compared using traditional methods. Consequently, the proposed approach can be a useful tool in benchmarking radar cross section reduction performance of metamaterial-based, and other types of scattering structures. Full article
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Article
Lightweight Physical Layer Aided Key Agreement and Authentication for the Internet of Things
Electronics 2021, 10(14), 1730; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141730 - 19 Jul 2021
Viewed by 323
Abstract
In this paper, we propose a lightweight physical layer aided authentication and key agreement (PL-AKA) protocol in the Internet of Things (IoT). The conventional evolved packet system AKA (EPS-AKA) used in long-term evolution (LTE) systems may suffer from congestion in core networks by [...] Read more.
In this paper, we propose a lightweight physical layer aided authentication and key agreement (PL-AKA) protocol in the Internet of Things (IoT). The conventional evolved packet system AKA (EPS-AKA) used in long-term evolution (LTE) systems may suffer from congestion in core networks by the large signaling overhead as the number of IoT devices increases. Thus, in order to alleviate the overhead, we consider cross-layer authentication by integrating physical layer approaches to cryptography-based schemes. To demonstrate the feasibility of the PL-AKA, universal software radio peripheral (USRP) based tests are conducted as well as numerical simulations. The proposed scheme shows a significant reduction in the signaling overhead, compared to the conventional EPS-AKA in both the simulation and experiment. Therefore, the proposed lightweight PL-AKA has the potential for practical and efficient implementation of large-scale IoT networks. Full article
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Article
Monitoring the Health and Residence Conditions of Elderly People, Using LoRa and the Things Network
Electronics 2021, 10(14), 1729; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141729 - 19 Jul 2021
Viewed by 361
Abstract
The rapid development and widespread use of information and telecommunication technologies do not mitigate, in many situations, information exclusion, nor the physical isolation of people—mainly that of the elderly living in remote locations, whose mobile network coverage is deficient or non-existent, preventing them [...] Read more.
The rapid development and widespread use of information and telecommunication technologies do not mitigate, in many situations, information exclusion, nor the physical isolation of people—mainly that of the elderly living in remote locations, whose mobile network coverage is deficient or non-existent, preventing them from accessing health care, be it routine follow-up procedures or emergencies. Addressing this, we raise the question that guides our study: how can we monitor the elderly’s residence and health conditions, detect falls, and track their movement in the vicinity of their homes in a non-intrusive manner? To answer this question, we present a system prototype that uses affordable, low-cost, and low-energy equipment with media and data processing, supported by LoRa (Long Range) and ESP32 microcontrollers, coupling several sensors. As a result, it is possible to monitor sensors that predict and detect falls or other risk events for the user, e.g., fire, with authorized persons and entities, family members, civil protection, and security forces accessing the gathered data, assuring their security. We conclude that the system could decisively improve people’s quality of life, particularly those of the elderly who live in remote places with greater vulnerability. Full article
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Article
The Impact of COVID-19 in Collaborative Programming. Understanding the Needs of Undergraduate Computer Science Students
Electronics 2021, 10(14), 1728; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141728 - 19 Jul 2021
Viewed by 437
Abstract
Collaborative learning activities have become a common practice in current university studies due to the implantation of the EHEA. However, the COVID-19 pandemic has led to a radical and abrupt change in the teaching–learning model used in most universities, and in the way [...] Read more.
Collaborative learning activities have become a common practice in current university studies due to the implantation of the EHEA. However, the COVID-19 pandemic has led to a radical and abrupt change in the teaching–learning model used in most universities, and in the way students’ group work is carried out. Given this new situation, our interest is focused on discovering how computer science students have approached group programming tasks. For this purpose, we have designed a cross-sectional pilot study to explore, from both social and technological points of view, how students carried out their group programming activities during the shutdown of universities, how they are doing them now, when social distance must be maintained, and what they have missed in both situations. The results of the study indicate that during the imposed confinement, the students adopted a programming model based on work division or distributed peer programming, and very few made use of synchronous distributed collaboration tools. After the lockdown, the students mostly opted for a model based on collaborative programming and there was an increased use of synchronous distributed collaboration tools. The specific communication, synchronization, and coordination functionalities they considered most useful or necessary were also analyzed. Among the desirable features included in a software for synchronous distributed programming, the students considered that having an audio-channel can be very useful and, possibly, the most agile method to communicate. The video signal is not considered as very necessary, being in many cases rather a source of distraction, while textual communication through a chat, to which they are very accustomed, is also well valued. In addition, version control and the possibility of recovering previous states of the practical projects were highly appreciated by the students, and they considered it necessary to record the individual contributions of each member of the team to the result. Full article
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Article
Design of Low Cross-Polarization Tri-Reflector CATR with Standard Quadric Surfaces Working in Terahertz
Electronics 2021, 10(14), 1727; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141727 - 18 Jul 2021
Viewed by 349
Abstract
In this paper, a tri-reflector compact antenna test range (CATR) consisting of a main parabolic reflector with a square aperture of 3 m in side length and two sub-reflectors of rotationally standard quadric surfaces working in terahertz is proposed. By using the equivalent [...] Read more.
In this paper, a tri-reflector compact antenna test range (CATR) consisting of a main parabolic reflector with a square aperture of 3 m in side length and two sub-reflectors of rotationally standard quadric surfaces working in terahertz is proposed. By using the equivalent paraboloid theory and cross-polarization elimination conditions and then combining with the appropriate shaped feed, the low cross-polarization and good quiet zone (QZ) performance of the system are achieved. The simulated results demonstrate that a cross-polarization isolation of >37 dB and a peak-to-peak amplitude (phase) ripple of <1.8 dB (13°) can be achieved on the principal cuts of the QZ at 100–500 GHz. At the same time, the QZ usage ratio of the CATR can reach 75%. The proposed tri-reflector CATR composed of standard quadric surfaces not only exhibits good quiet zone performance but also greatly reduces the manufacturing difficulty of the sub-reflectors and the construction cost of the system. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Article
Improved Droop Control Strategy of Multiple Energy Storage Applications in an AC Microgrid Based on the State of Charge
Electronics 2021, 10(14), 1726; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141726 - 18 Jul 2021
Viewed by 369
Abstract
Distributed energy storage technology is used to stabilize the frequency and voltage of the microgrid operating in islanded mode. However, due to the inconsistent state of charge (SoC) of the energy storage unit (ESU), the active power output of the ESU [...] Read more.
Distributed energy storage technology is used to stabilize the frequency and voltage of the microgrid operating in islanded mode. However, due to the inconsistent state of charge (SoC) of the energy storage unit (ESU), the active power output of the ESU cannot be shared reasonably. On the basis of stabilizing voltage and frequency, this paper presents a power exponential function droop control (PEFDC) strategy considering the SoC. In this control strategy, the ESU is allowed to adjust the output power adaptively according to its own SoC level during discharge and reaches SoC equilibrium. Simulation models are built to compare the PEFDC strategy with conventional droop control (CDC) and power function droop control (PFDC) approaches. The simulation results illustrate the superiority of the proposed control strategy over the other two methods. Finally, the hardware-in-the-loop experiment is conducted to verify the effectiveness of the PEFDC strategy. Full article
(This article belongs to the Section Power Electronics)
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Article
Office Room Channel Modeling and Object Attenuation at Sub-THz Frequencies
Electronics 2021, 10(14), 1725; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141725 - 18 Jul 2021
Viewed by 392
Abstract
Large bandwidths are needed to meet the high-throughput requirements of future wireless communication systems. These larger bandwidths are available at mmWave and sub-THz frequencies, such as the V-band ranging from 50 to 75 GHz and the D-band ranging from 110 to 170 GHz. [...] Read more.
Large bandwidths are needed to meet the high-throughput requirements of future wireless communication systems. These larger bandwidths are available at mmWave and sub-THz frequencies, such as the V-band ranging from 50 to 75 GHz and the D-band ranging from 110 to 170 GHz. In this paper, we present channel measurements in an office environment, covering the full D-band. Line-of-Sight (LOS) path loss (PL) is modeled as a function of frequency and distance. Both a single-frequency floating-intercept and multi-frequency alpha-beta-gamma model provide a good fit to the measured LOS PL data. Attenuation due to blockage of the LOS path by various desk objects, such as computer peripherals and cables, is determined, as well as attenuation due to plant obstructions. Attenuation due to an obstructed LOS path ranges from 3 dB for a single universal serial bus (USB) cable, and up to 25 dB for a laptop power supply, computer mouse, computer monitor, or plant. Because of a higher diffraction angle, the measured attenuation is higher when the distance between the antennas decreases. We measure diffraction around a computer monitor for dual polarization and verify whether communication via the reflected non Line-of-Sight path makes high-throughput wireless communication possible when the LOS path is blocked. Full article
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Article
Token-Based Authentication Framework for 5G MEC Mobile Networks
Electronics 2021, 10(14), 1724; https://doi.org/10.3390/electronics10141724 - 18 Jul 2021
Viewed by 587
Abstract
MEC technology provides a distributed computing environment in 5G mobile networks for application and service hosting. It allows customers with different requirements and professional competencies to use the services offered by external suppliers. We consider a service access control framework on 5G MEC [...] Read more.
MEC technology provides a distributed computing environment in 5G mobile networks for application and service hosting. It allows customers with different requirements and professional competencies to use the services offered by external suppliers. We consider a service access control framework on 5G MEC networks that is efficient, flexible, and user-friendly. Its central element is the MEC Enabler, which handles AAA requests for stakeholders accessing services hosted on the edge servers. The JSON Web Token (JWT) open standard is a suitable tool for the MEC Enabler to manage access control credentials and transfer them securely between parties. In this paper, in the context of access control, we propose the token reference pattern called JSON MEC Access Token (JMAT) and analyze the effectiveness of its available protection methods in compliance with the standard requirements of MEC-hosted services in 5G networks. Full article
(This article belongs to the Special Issue Cybersecurity and Mobility in 5G and Beyond)
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Article
Interference Mitigation and Power Minimization in 5G Heterogeneous Networks
Electronics 2021, 10(14), 1723; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141723 - 18 Jul 2021
Viewed by 365
Abstract
Macro cells’ (MCs) densification with small cells (SCs) is one of the promising solutions to cope with the increasing demand for higher data rates in 5G heterogeneous networks (HetNets). Unfortunately, the interference that arises between these densely deployed SCs and their elevated power [...] Read more.
Macro cells’ (MCs) densification with small cells (SCs) is one of the promising solutions to cope with the increasing demand for higher data rates in 5G heterogeneous networks (HetNets). Unfortunately, the interference that arises between these densely deployed SCs and their elevated power consumption have caused huge problems facing the 5G HetNets. In this paper, a new soft frequency reuse (SFR) scheme is proposed to minimize the interference and elevate the network throughput. The proposed scheme is based on on/off switching the SCs according to their interference contribution rate (ICR) values. It solves the interference problem of the densely deployed SCs by dividing the cell region into center and edge zones. Moreover, SCs on/off switching tackles the elevated power consumption problem and enhances the power efficiency of the 5G network. Furthermore, our paper tackles the irregular nature problem of 5G HetNets and compares between two different proposed shapes for the center zone of the SC: circular, and irregular shapes. Additionally, the optimum radius of the center zone, which maximizes the total system data rate, is obtained. The results show that the proposed scheme surpasses the traffic and the random on/off switching schemes, as it decreases the outage probability and enhances the total system data rate and power efficiency. Moreover, the results demonstrate the close performance of both the irregular and circular shapes for the center zone. Full article
(This article belongs to the Special Issue Spectrum and Energy Efficient 5G Wireless Communications)
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Article
Lumped Parameter Modeling Based Power Loop Analysis Technique of Power Circuit Board with Wide Conduction Area for WBG Semiconductors
Electronics 2021, 10(14), 1722; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141722 - 18 Jul 2021
Viewed by 592
Abstract
With the development of wide-bandgap (WBG) power semiconductor technology, such as silicon carbide (SiC) and gallium nitride (GaN), the technology of power converters with high efficiency and high-power density is rapidly developing. However, due to the high rate-of-rise of voltage (dv/dt) [...] Read more.
With the development of wide-bandgap (WBG) power semiconductor technology, such as silicon carbide (SiC) and gallium nitride (GaN), the technology of power converters with high efficiency and high-power density is rapidly developing. However, due to the high rate-of-rise of voltage (dv/dt) and of current (di/dt), compared to conventional Si-based power semiconductor devices, the reliability of the device is greatly affected by the parasitic inductance component in the switching loop. In this paper, we propose a power loop analysis method based on lumped parameter modeling of a power circuit board with a wide conduction area for WBG power semiconductors. The proposed analysis technique is modeled based on lumped parameters, so that power loops with various current paths can be analyzed; thus, the analysis is intuitive, easy to apply and realizes dynamic power loop analysis. Through the proposed analysis technique, it is possible to derive the effective parasitic inductance component for the main points in the power circuit board. The effectiveness of the lumped parameter model is verified through PSpice and Ansys Q3D simulation results. Full article
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Article
Multi-Objective Energy Management Strategy for PV/FC Hybrid Power Systems
Electronics 2021, 10(14), 1721; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141721 - 18 Jul 2021
Viewed by 427
Abstract
In this paper, a new control of the DC–DC power converter that interfaces the fuel cell (FC) system with the DC bus of the photovoltaic (PV) power system is proposed to increase the battery lifespan by its operating in charge-sustained mode. Thus, the [...] Read more.
In this paper, a new control of the DC–DC power converter that interfaces the fuel cell (FC) system with the DC bus of the photovoltaic (PV) power system is proposed to increase the battery lifespan by its operating in charge-sustained mode. Thus, the variability of the PV power and the load demand is compensated by the FC power generated considering the power flows balance on the DC bus. During peak PV power, if the PV power exceeds the load demand, then the excess power on the DC bus will power an electrolyzer. The FC system operation as a backup energy source is optimized using a new fuel economy strategy proposed for fueling regulators. The fuel optimization function considers the fuel efficiency and electrical efficiency of the FC system to maximize fuel economy. The fuel economy obtained in the scenarios considered in this study is compared with reference strategies reported in the literature. For example, under scenarios considered in this paper, the fuel economy is between 4.82–20.71% and 1.64–3.34% compared to a commercial strategy based on static feed-forward (sFF) control and an advanced strategy recently proposed in the literature, respectively. Full article
(This article belongs to the Special Issue Photovoltaic Energy Systems and Storage)
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Article
An Isolated Power Factor Corrected Cuk Converter with Integrated Magnetics for Brushless DC Ceiling Fan Applications
Electronics 2021, 10(14), 1720; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141720 - 17 Jul 2021
Viewed by 502
Abstract
The usage of BLDC motors in the low-power range is increasing rapidly in home appliances such as ceiling fans. This has necessitated the development of reliable, compact and efficient AC-DC power supplies for motor drive circuitry. This paper presents a power supply design [...] Read more.
The usage of BLDC motors in the low-power range is increasing rapidly in home appliances such as ceiling fans. This has necessitated the development of reliable, compact and efficient AC-DC power supplies for motor drive circuitry. This paper presents a power supply design consisting of an AC-DC isolated PFC Cuk converter with integrated magnetics that supplies a single-shunt voltage source inverter for the sensorless drive of the BLDC fan motor. The proposed power supply design is comprised of an integrated magnetics structure in which the two inductors and the transformer windings share the same core. The zero input and output ripple current conditions have been derived from the reluctance model of the magnetic assembly. Smooth operation of the motor by minimizing the motor torque ripples is evident from the results. The Cuk converter operates in continuous conduction mode (CCM), employing the current multiplier method. The CCM-based current multiplier control loop ensures a near-unity power factor as well as low total harmonic distortion in the supply current. The current loop also provides over-current protection, enhancing reliability of the system. Moreover, the speed of the BLDC motor is controlled by the field oriented control (FOC) algorithm, which enables direct operation with alternate energy sources such as batteries and solar photovoltaic panels. The performance of the proposed supply is validated: motor torque ripple is reduced to only 2.14% while maintaining 0.999 power factor and only 4.72% THD at full load. Failure modes analysis has also been performed through software simulations, using the PLECS simulation environment. Due to the reliable power supply design with low ripples, it is well suited for low-power BLDC motors in home appliances and small power tools, in addition to ceiling fans. Full article
(This article belongs to the Section Power Electronics)
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Article
Multi-Layer Latency Aware Workload Assignment of E-Transport IoT Applications in Mobile Sensors Cloudlet Cloud Networks
Electronics 2021, 10(14), 1719; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141719 - 17 Jul 2021
Cited by 5 | Viewed by 1043
Abstract
These days, with the emerging developments in wireless communication technologies, such as 6G and 5G and the Internet of Things (IoT) sensors, the usage of E-Transport applications has been increasing progressively. These applications are E-Bus, E-Taxi, self-autonomous car, E-Train and E-Ambulance, and latency-sensitive [...] Read more.
These days, with the emerging developments in wireless communication technologies, such as 6G and 5G and the Internet of Things (IoT) sensors, the usage of E-Transport applications has been increasing progressively. These applications are E-Bus, E-Taxi, self-autonomous car, E-Train and E-Ambulance, and latency-sensitive workloads executed in the distributed cloud network. Nonetheless, many delays present in cloudlet-based cloud networks, such as communication delay, round-trip delay and migration during the workload in the cloudlet-based cloud network. However, the distributed execution of workloads at different computing nodes during the assignment is a challenging task. This paper proposes a novel Multi-layer Latency (e.g., communication delay, round-trip delay and migration delay) Aware Workload Assignment Strategy (MLAWAS) to allocate the workload of E-Transport applications into optimal computing nodes. MLAWAS consists of different components, such as the Q-Learning aware assignment and the Iterative method, which distribute workload in a dynamic environment where runtime changes of overloading and overheating remain controlled. The migration of workload and VM migration are also part of MLAWAS. The goal is to minimize the average response time of applications. Simulation results demonstrate that MLAWAS earns the minimum average response time as compared with the two other existing strategies. Full article
(This article belongs to the Special Issue 10th Anniversary of Electronics: Advances in Networks)
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Article
Error-Tolerant Reconfigurable VDD 10T SRAM Architecture for IoT Applications
Electronics 2021, 10(14), 1718; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141718 - 17 Jul 2021
Viewed by 805
Abstract
This paper proposes an error-tolerant reconfigurable VDD (R-VDD) scaled SRAM architecture, which significantly reduces the read and hold power using the supply voltage scaling technique. The data-dependent low-power 10T (D2LP10T) SRAM cell is used for the R-VDD scaled architecture with the [...] Read more.
This paper proposes an error-tolerant reconfigurable VDD (R-VDD) scaled SRAM architecture, which significantly reduces the read and hold power using the supply voltage scaling technique. The data-dependent low-power 10T (D2LP10T) SRAM cell is used for the R-VDD scaled architecture with the improved stability and lower power consumption. The R-VDD scaled SRAM architecture is developed to avoid unessential read and hold power using VDD scaling. In this work, the cells are implemented and analyzed considering a technologically relevant 65 nm CMOS node. We analyze the failure probability during read, write, and hold mode, which shows that the proposed D2LP10T cell exhibits the lowest failure rate compared to other existing cells. Furthermore, the D2LP10T cell design offers 1.66×, 4.0×, and 1.15× higher write, read, and hold stability, respectively, as compared to the 6T cell. Moreover, leakage power, write power-delay-product (PDP), and read PDP has been reduced by 89.96%, 80.52%, and 59.80%, respectively, compared to the 6T SRAM cell at 0.4 V supply voltage. The functional improvement becomes even more apparent when the quality factor (QF) is evaluated, which is 458× higher for the proposed design than the 6T SRAM cell at 0.4 V supply voltage. A significant improvement of power dissipation, i.e., 46.07% and 74.55%, can also be observed for the R-VDD scaled architecture compared to the conventional array for the respective read and hold operation at 0.4 V supply voltage. Full article
(This article belongs to the Special Issue Test and Monitoring of Aging Effects in Electronics)
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Article
Multi-Kernel Polar Codes versus Classical Designs with Different Rate-Matching Approaches
Electronics 2021, 10(14), 1717; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10141717 - 17 Jul 2021
Viewed by 365
Abstract
Polar codes, which have been proposed as a family of linear block codes, has garnered a lot of attention from the scientific community, owing to their low-complexity implementation and provably capacity-achieving capability. Thus, they have been proposed to be used for encoding information [...] Read more.
Polar codes, which have been proposed as a family of linear block codes, has garnered a lot of attention from the scientific community, owing to their low-complexity implementation and provably capacity-achieving capability. Thus, they have been proposed to be used for encoding information on the control channels in the upcoming 5G wireless networks. The basic approach introduced by Arikan in his landmark paper to polarize bit channels of equal capacities to those of unequal capacities can be used to design only codewords of length N=2n, which is a major limitation when codewords of different lengths are required for the underlying applications. In the predecessor paper, this aspect was partially addressed by using a 3×3 kernel circuit (used to generate codewords of length M=3m), along with downsizing techniques such as puncturing and shortening to asses the optimal design and resizing techniques based on the underlying system parameters. In this article, we extend this research to include the assessment of multi-kernel rate-matched polar codes for applicability over a much wider range of codeword lengths. Full article
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