Wireless Systems Research Articles

2-D deployment of aerial base stations: A simulation model to provide voice communication

Unmanned aerial vehicles (UAVs) offer a potential alternative for providing voice services in areas where communication is disrupted due to natural disasters. These UAVs can be configured as aerial base stations (ABSs), enabling the deployment of a temporary communications network. However, communication networks based on ABSs pose several significant challenges. One of these challenges involves addressing interruptions or limitations in network coverage caused by natural disasters. In such situations, there is a high likelihood that users within the affected area may be unable to communicate due to a lack of coverage. This is a complex problem because it depends on factors, such as the mobile user locations, the characteristics of the air-to-ground channel, and geographical details of the area. In this work, we propose an optimization model to determine the placement of a set of ABSs within a limited disaster area that maximizes the probability of successful voice services (PSVSs). This optimization model integrates a network evaluation model that analyzes the wireless environment at a specific time. The network evaluation model utilizes two-ray and Rayleigh channel models, enabling the simulation of a worst-case scenario for wireless communication systems. We evaluate the proposed optimization model using the (1+1)-evolution strategy with a one-fifth success rule. We explore various parameter configurations to understand their impact on algorithm performance. This analysis helps identify the configuration of the optimization model that yields the maximum PSVSs. Simulation results indicate that by appropriately configuring the evolution strategy algorithm and comparing random ABS locations with those determined ABS locations by the evolution strategy algorithm, the PSVS can be enhanced by an average of 60%.

A real-time seed spacing wireless remote online measurement system: Investigating factors influencing measurement accuracy, determining the optimal installation position for seed sensors to improve measurement precision

A real-time seed spacing wireless remote online measurement system: Investigating factors influencing measurement accuracy, determining the optimal installation position for seed sensors to improve measurement precision

A study of the magnetic field emissions from a vehicle-mounted wireless power transfer system for safe operation when charging EV batteries

A study of the magnetic field emissions from a vehicle-mounted wireless power transfer system for safe operation when charging EV batteries

IoT-Based Metal Detector Robot with Wireless Surveillance

Abstract: This project presents the design and development of an IoT-based metal detector robot equipped with wireless surveillance capabilities. The robot is designed to autonomously navigate its environment while detecting metallic objects underground, with real-time monitoring provided through a wireless camera system. The core components of the system include a metal detector sensor, an ESP8266 NodeMCU for wireless communication, an L298 motor driver for controlling the robot’s movement, and a surveillance camera for live video streaming. The system is powered by 3.7V battery cells, ensuring mobility and operational autonomy.The metal detector sensor scans for metallic objects, and upon detection, an alert is generated. Simultaneously, a wireless camera transmits real-time footage, allowing remote monitoring and control via a web interface or mobile device. The robot's movement is controlled through a second ESP8266 module, enabling wireless command inputs for navigation.This robot is envisioned for use in security applications, such as detecting landmines or hazardous metallic objects in sensitive areas, as well as for archaeological and construction projects. The integration of IoT technology enhances the robot’s operational range and effectiveness, providing a scalable solution for remote metal detection and surveillance.The integration of IoT technology significantly enhances the system's operational efficiency and range, enabling seamless remote control and monitoring. This innovation not only improves safety in hazardous conditions but also increases the effectiveness of metal detection and surveillance tasks in diverse environments

Rate maximization based on soft actor-critic reset for RIS-assisted MU-MISO symbiotic radio systems

Rate maximization based on soft actor-critic reset for RIS-assisted MU-MISO symbiotic radio systems

Design of a Current-Mode Trapezoidal Waveform Generator in High-Voltage SOI Technology with Modifications Based on Safe Operating Area Limits

Integrated circuits are the core building components of virtually all communication systems. Wireless communication systems are becoming increasingly common. They require specialized transmission components to reduce electromagnetic interference. This paper presents the design of a trapezoidal waveform generator intended for generation of waveforms with limited level and spectrum of radiated interference This limitation is important because the discussed circuit is a high-voltage function block that can drive the output antenna with relatively high-power pulses. The introduced design is based on a mix of low- and high-voltage devices; however, most of them operate in low-voltage steady and near steady conditions. The implemented design flow includes safe operating area controls, which result in the implementation of a set of overvoltage devices. The designed generator provides means of frequency and slew rate control and can produce high-quality output waveforms. The results show that this type of design can be further optimized for generating waveforms with a limited range of slew rate values. Moreover, this paper presents some operational aspects and phenomena that must be addressed to provide a design that can be practically implemented in modern high-voltage integrated circuits.

Adaptive Strategies in Enhancing Physical Layer Security: A Comprehensive Survey

Adaptive schemes in physical layer security, designed to dynamically respond to the evolving conditions of wireless channels, play a crucial role in fortifying the security of wireless communication systems. We offer a thorough analysis of the current state of research on adaptive schemes in physical layer security, introducing a novel taxonomy to categorize and understand these schemes more effectively. A detailed comparison is drawn between the insights provided in this survey and those from the literature, highlighting the unique contributions of our work. We delve into the contributions and challenges associated with various adaptive schemes, providing valuable lessons and summaries to guide further research. The future research directions of the adaptive scheme are discussed in Part 2 of the Appendix, aiming to address the current and emerging demands of wireless communication systems. Through this survey, we aim to enrich the discourse on adaptive schemes in physical layer security, paving the way for advanced research and development in enhancing the security of wireless networks.

Review on the Applications of Intelligent Algorithm in Wireless Charging System for Electric Vehicles

This paper presents a comprehensive review of the intelligent algorithms (IAs) based optimization of electric vehicle (EV) wireless charging. First, a general overview of EV wireless charging system is introduced in terms of the compensation circuit, coupling coils, and control strategies, followed by the potential application of IAs. Then, the optimization target, parameter optimization, and structure design of the compensation topologies based on IAs are elaborately expounded by citing current research findings. Subsequently, the IAs are deeply explored for optimizing the systematic parameters, structural geometries, and coupling coils. Then, the IA-based research on the control strategies in the wireless charging system is discussed in detail from three aspects, including power controlling, efficiency optimizing, and parameter tracking. Finally, the prospects for the application of IAs to the EV wireless charging system are summarized and delineated. This paper will be highly beneficial to research entities as a ready reference for the wireless charging system of EVs, with information on IA-based system design.

Embedded Water-lubricated Bearing Temperature Wireless Monitoring System

For the ship lubrication system, different water temperatures not only affect the viscosity coefficient of the water, but also cause additional thermal deformation of the rubber bearing, and in serious cases, it also affects the normal operation of the ship lubrication system. However, the water film has a closed area, various bearing structures, complex operating conditions, and limited existing monitoring methods, resulting in accurate temperature data that is not easy to obtain. In order to solve the above problems, a thin-film temperature sensor was proposed to be embedded in the water-lubricated bearing and wireless communication technology was applied, and a monitoring system was developed to achieve real-time monitoring of the bearing temperature signal. Firstly, the temperature monitoring system and bearing system are described, then the temperature sensor is calibrated, and finally the system is designed and tested through software and hardware. The results show that the method of the wireless temperature monitoring system in this paper is feasible.

Golden Angle Modulation in Complex Dimension Two

In this paper, we propose a new geometric-shaping design for golden angle modulation (GAM) based on the complex geometric properties of open symmetrized bidisc, termed Bd-GAM, for future generation wireless communication systems. Inspired from the circular symmetric structure of the GAM, we construct the modulation schemes, Bd-GAM1 and Bd-GAM2. Specifically, we consider MI-optimized probabilistic modulation scheme with the geometrics properties of symmetric bidisc. With minimum SNR and entropy constraint, Bd-GAM1 and Bd-GAM2 can overcome the shaping-loss. Compared with the existed golden angle modulation introduced, the new design improves the mutual information, and the distance between adjacent constellation points.

Deep Learning Framework Using Spatial Attention Mechanisms for Adaptable Angle Estimation Across Diverse Array Configurations

Rapid advancement of wireless communication systems and the increasing need for accurate, real-time signal processing have driven innovations in direction-of-arrival (DoA) estimation techniques. This paper introduces a novel convolutional neural network (CNN) architecture that combines spatial attention mechanisms with a transfer learning framework to enhance both accuracy and versatility in DoA estimation. The model integrates spatial attention layers to dynamically prioritize signal regions with the highest information value, allowing it to isolate relevant signals and suppress interference in noisy or crowded signal environments. In addition, we utilize a transfer learning framework that enables the model to generalize across various antenna array configurations (i.e., planar, linear, and circular arrays) with minimal additional training. Extensive simulation results benchmark the proposed model against existing state-of-the-art methods for DoA estimation, achieving improved absolute error across diverse conditions. This hybrid approach not only enhances DoA estimation precision, but also significantly reduces retraining requirements when adapting to new array configurations, positioning it as a robust, scalable tool for next-generation wireless communication systems.

Changes in Cerebral Hemodynamic Among Patients With Schizophrenia or Bipolar Disorder Receiving Electroconvulsive Therapy: A Task-Related Functional Near-Infrared Spectroscopy Study.

There remains a scarcity of studies to evaluate the treatment effect of electroconvulsive therapy (ECT). Functional near-infrared spectroscopy (fNIRS) offers a cost-effective method to measure cerebral hemodynamics. This study used fNIRS to evaluate the effect of ECT in patients suffering from schizophrenia or bipolar disorder (manic phase). Thirty patients with mania and 31 with schizophrenia were recruited. Each participant received 6 sessions of ECT. This study utilized the Positive and Negative Syndrome Scale, Young Mania Rating Scale, and fNIRS-verbal fluency test paradigm at baseline and after each session of ECT. The prefrontal cortex hemodynamic response during the performance of verbal fluency test was recorded via a commercial wireless high-density continuous-wave fNIRS system device. The effect of categorical and continuous variables was determined using Pearson's chi-square test and Student's t test or 1-way analysis of variance with Bonferroni-corrected post hoc pairwise comparison, respectively. Comparing the Positive and Negative Syndrome Scale and Young Mania Rating Scale scores between baseline, sessions 3 and 6, the scores were significantly decreased (P < 0.001), with both patient groups achieving more than 50% reduction in scores from baseline to session 6. The fNIRS also showed significant increases in oxy-hemoglobin levels (session 6 vs baseline) in the right ventrolateral prefrontal cortex and left dorsolateral prefrontal cortex for both patient groups (P < 0.05). There were significant correlations in the reduction of symptom severity and increase in HbO2 levels in people with bipolar disorder (manic phase) and schizophrenia (P < 0.05). Monitoring the activation in the right ventrolateral prefrontal cortex and left dorsolateral prefrontal cortex is an objective ECT monitoring indicator for patients suffering from bipolar disorder (manic phase) or schizophrenia.

Two-dimensional integrated optical phased array with high fill-factor antennas.

A silicon photonics optical phased array with a two-dimensional matrix of antennas is experimentally demonstrated in which the unitary antennas are optimized such that light can be emitted over a high fraction of the overall array surface. This design strategy can be used to obtain a low divergence emitted beam containing a significant fraction of the total emitted power, at the expense of a reduced beam steering range. This type of device can be suited to phase front correction in optical wireless communications systems.

Innovative Capacitive Wireless Power System for Machines and Devices

This article deals with the design, development, and analysis of a wireless power transfer system prototype based on capacitive coupling. The system is intended for the continuous charging of a suspended mine drivetrain. It consists of a resonant inverter, primary and secondary matching circuits, a suitable capacitive coupler, and a rectifier with a load, ultimately serving as a battery charger for a mobile energy storage device. The system successfully achieved the target output voltage of 320 V and a charger output power of 2 kW at an operating frequency of 300 kHz. Additionally, the total system efficiency was at the level of 60%, ensuring that the RMS voltages on passive components remained below 3 kV.

Adapting the Formula for Planar Spiral Inductors’ Inductance Computation to the New Oval Geometric Shape, Ideal for Designing Wireless Power Transfer Systems for Smart Devices

The most used spiral inductors, in the available scientific literature and in our research activities, so far, have been those with square, hexagonal, octagonal, and circular geometric shapes. Geometry plays an important role in the efficiency of these inductors when used in wireless power transfer. In this article, a new geometric shape is designed by combining the square and the circle to create an oval shape of a planar spiral inductor. Inductors with this new shape are designed, numerically modelled, and practically constructed for experimental testing. The formula for inductance computation for planar spiral inductors is adapted for this new oval shape. New geometric coefficients, required for inductance computation formula, have been determined. The new formula for inductance computation is validated both analytically, by comparing the results with those from numerical modelling, and experimentally, by comparing with measurements, for a wide range of oval spiral inductors. Five sets of different oval spiral inductors are optimally designed, numerically modelled, practically constructed, and experimentally tested. By designing this new shape for planar spiral inductors, the inductance is increased 2.16 times compared to square, 1.84 times compared to hexagonal, 2.12 times compared to octagonal, and 2.52 times compared to circular shapes. The new oval spiral inductor design will be very useful for constructing wireless power transfer systems for pacemakers, smartphones, smartwatches, and/or any other type of smart device.

Machine learning-based spectrum occupancy prediction: a comprehensive survey

In cognitive radio (CR) systems, efficient spectrum utilization depends on the ability to predict spectrum opportunities. Traditional statistical methods for spectrum occupancy prediction (SOP) are insufficient for addressing the non-stationary nature of spectrum occupancy, especially with UEs’ increased mobility and diversity in the sixth-generation and beyond wireless networks. This survey provides a comprehensive overview of machine learning (ML)-based SOP methods that address these challenges. The paper begins with a brief discussion of problem definition and traditional statistical methods before delving into a detailed survey of ML-based methods. Various aspects of SOP are analyzed from a CR perspective, highlighting the multidimensional correlations in spectrum usage across time, frequency, space, etc. Key challenges and enabling methods for effective prediction are reviewed, focusing on deep learning methods that exploit these multidimensional correlations. The survey also covers dataset generation techniques for SOP. Additionally, the paper discusses CR threats that impair spectrum utilization and reviews ML methods for detecting these threats. The future directions for ML-based SOP are also given.

Electromagnetic properties of Ni–Zn–Cu ferrite as magnetic sheet in wireless charging system

AbstractTo obtain high‐performance magnetic sheet with high initial permeability and low magnetic loss for wireless charging system, Ni–Zn–Cu ferrite ceramics with a chemical formula of Ni0.6 − xZn0.4CuxFe2O4 (x = 0–0.30) were prepared by traditional solid reaction‐sintering method. As expected, the doped Cu2+ ions could effectively reduce the sintering temperature and increase the density of the ferrites. With increasing doping amount of Cu2+, the coercivity, saturation magnetization, and Curie temperature of the resultant ferrites decreased. With x = 0.15, the sample presented the maximum initial magnetic permeability and highest Q‐factor. On the basis of the measured magnetic parameters, the ferrites were examined as magnetic sheet in wireless charging system by digital simulation, while the structural parameters of the system were considered and the coefficients of hysteresis loss, eddy current loss, and excess loss were quantitatively separated under sinusoidal excitation. Specifically, because of its lower core loss, the optimal ferrite (x = 0.15) would perform better with much improved transmission efficiency than that without the doping of Cu2+, especially when the transmitting and receiving coils were settled more apart, which might be a good candidate for wireless charging system, and the proposed simple wireless charging system can be used as a general strategy for the evaluation of magnetic sheets.

Programmable beam steering and quasi-continuous phase shift on a 2-bit terahertz coding metasurface with HEMT-switched multimodal modulation.

Terahertz reconfigurable intelligent surfaces (RIS) stand out from conventional phased arrays thanks to their unique electromagnetic properties and intelligent interconnect paradigms. They are a vital technology for terahertz wireless communication and radar detection systems. Compared with 1-bit coding metasurfaces, 2-bit coding metasurfaces offer significant advantages such as single beam steering and reduced quantization errors. Electrically controlled switchable coding metasurfaces have been restricted by the switch performance and integration technology, limiting reported devices to 1-bit coding. Additionally, metasurfaces that offer quasi-continuous phase modulation across a 2π range have garnered extensive attention for their higher phase shift precision and regulation freedom. This paper proposes a 2-bit multimodal THz quasi-continuous phase shift coding metasurface based on asymmetrically configured high electron mobility transistor (HEMT)-dipoles. The meta-device consists of two asymmetrically combined HEMT-dipole resonant structures, wherein the versatile density variations of two-dimensional electron gas (2DEG) introduce subtly local-field modulation under different external voltage combinations, rendering the quasi-continuous phase shift of 0° to 350° at 0.376 THz with a minimum incremental step of 6°. Moreover, selecting optimal 2-bit coding states within the quasi-continuous phase shift loop constructed different array phase gradients based on Snell's law, enabling real-time beam steering from 21° to 48° within the 0.365-0.385 THz frequency range. The simulation results align closely with the experimental findings, marking the first achievement of real-time programmable phase shift control and 2-bit beam steering using electrically controlled switches in the terahertz domain. This research provides a practical approach for real-time quasi-optical continuous phase modulation control and programmable single-beam electronic steering, with promising applications in terahertz wireless communication, radar detecting, and computational imaging, among other fields.

Synchronous enhancement of safety protection and impact perception in intelligent leather

High protection performance and intelligence are gradually becoming indispensable key factors with the ever-improving personal protective equipment. However, protective material that can not only resist but also percept full type of impacts is an urgent need due to complex combat scenarios. This work reports an intelligent leather/shear stiffening gel (SSG)/Kevlar-shear thickening fluid (STF)/non-woven fabric (LSKSN) composite, which exhibits superior and comprehensive impact resistance performance in needle puncture, knife puncture, ballistic impact, and blunt impact. Especially, the LSKSN composite not only improves the puncture resistance performance by 71% but also still maintains a large resistance after being punctured. Moreover, the LSKSN composite possesses a high limit penetrated velocity of 159 m s−1 and can dissipate a high impact energy of 24.6 J, causing the bulletproof to be improved by 22%. Due to the excellent force-buffering performance and rate-dependent energy dissipation characteristics in wide-impact energy, the maximum energy dissipation rate of the LSKSN composite reaches 95%. Simultaneously, the further developed electronic LSKSN (E-LSKSN) composite shows outstanding perceptual capability, which is sensitive to various impacts and can accurately identify the impact types through different resistance changes (10–8000%) and response times (0.1–100 ms). Finally, based on the bending sensing and impact sensing properties of the E-LSKSN composite, a wireless signal transmission system is constructed to monitor the safety and movement status of the human body in real-time, which demonstrates this LSKSN composite possesses high potential in the next generation of intelligent protective equipment.Graphical

Wireless power transfer empowered by reconfigurable intelligent surfaces

ABSTRACT Reconfigurable Intelligent Surfaces (RIS) represent a significant advancement in hardware technology, enhancing both wireless energy and spectral efficiency within wireless communication systems. Comprising a programmable metasurface, RIS can adeptly manipulate the wavefronts of incident signals – encompassing parameters such as phase, amplitude, frequency, and polarisation – without necessitating complex signal processing techniques. The integration of RIS into wireless communication networks enables the strategic manipulation of radio waves, thereby mitigating the adverse effects associated with natural wireless propagation. This study examines a multi-user (MU) multiple-input multiple-output (MIMO) wireless power transfer (WPT) system augmented by multiple RISs, wherein the transmitter is equipped with a constant-envelope beamformer. The optimisation of the phase shifts of the RIS and the beamformer of the transmitter is conducted jointly to maximise the total power received by users. An alternating optimisation approach is proposed, utilising the semidefinite relaxation (SDR) method. Additionally, a problem is formulated to maximise the total received power while adhering to constraints on the minimum power received by users, thereby addressing issues of user fairness. To resolve this problem, an iterative algorithm based on the Alternating Direction Method of Multipliers (ADMM) is introduced. Analysis and simulation results indicate a significant enhancement in total received power when employing the proposed methodology compared to existing algorithms documented in the literature. Furthermore, in scenarios involving multiple users, a detailed analysis of the system’s transmission performance, facilitated by RIS, is conducted. The numerical results substantiate the validity of the analysis and demonstrate the efficacy of the proposed algorithms.