Advanced Communication Systems Research Articles

Enhanced polarization sensitivity and tunability in truncated pyramidal GaAs quantum dots for FIR applications

The far-infrared (FIR) spectrum, covering wavelengths from 20 to 1000 μm, presents significant challenges for the manipulation and detection of polarized light, especially in the short-wavelength FIR range of 20–100 μm. This study investigates the effectiveness of truncated pyramidal GaAs quantum dots in improving the absorption coefficient of polarized light within this range. Utilizing the finite difference method to obtain numerical solutions of the Schrödinger equation within the adiabatic approximation, we analyze the effects of various base shapes—equilateral hexagon, irregular hexagon, and equilateral triangle—on the optical absorption coefficients when subjected to an electric field with different directions and magnitudes. Our results reveal that triangular pyramidal quantum dots offer enhanced polarization sensitivity and greater tunability of absorption peaks compared to structures with other base shapes. Moreover, the direction of the applied electric field is crucial for tuning the absorption peaks in the desired range of FIR wavelength. These findings demonstrate the potential of truncated pyramidal GaAs quantum dots not only for improving sensing technologies but also for managing electromagnetic interference in advanced communication systems.

HCTC: Hybrid Convolutional Transformer Classifier for Automatic Modulation Recognition

Automatic modulation recognition (AMR) methods used in advanced wireless communications systems can identify unknown signals without requiring reference information. However, the acceptance of these methods depends on the accuracy, number of parameters, and computational complexity. This study proposes a hybrid convolutional transformer classifier (HCTC) for the classification of unknown signals. The proposed method utilizes a three-stage framework to extract features from in-phase/quadrature (I/Q) signals. In the first stage, spatial features are extracted using a convolutional layer. In the second stage, temporal features are extracted using a transformer encoder. In the final stage, the features are mapped using a deep-learning network. The proposed HCTC method is investigated using the benchmark RadioML database and compared with state-of-the-art methods. The experimental results demonstrate that the proposed method achieves a better performance in modulation signal classification. Additionally, the performance of the proposed method is evaluated when applied to different batch sizes and model configurations. Finally, open issues in modulation recognition research are addressed, and future research perspectives are discussed.

Investigation of optical soliton solutions for the cubic-quartic derivative nonlinear Schrödinger equation using advanced integration techniques

This paper aims to investigate optical soliton solutions in the context of the cubic-quartic derivative nonlinear Schrödinger equation with differential group delay, incorporating perturbation terms for the first time. Motivated by the need to better understand soliton dynamics in advanced optical communication systems, we employ three integration techniques: the direct algebraic approach, Kudryashov’s method with an addendum, and the unified Riccati equation expansion method. Our study reveals that, by appropriately selecting parameter values, the resulting solutions include Jacobi elliptic functions that describe straddle solitons, bright, dark, and singular solitons. We also identify the conditions under which these soliton pulses can exist. Furthermore, we provide numerical simulations to illustrate these solutions under specific parameter settings, highlighting their potential applications in optical fiber systems.

A Review on Millimeter-Wave Hybrid Beamforming for Wireless Intelligent Transport Systems

As the world braces for an era of ubiquitous and seamless connectivity, hybrid beamforming stands out as a beacon guiding the evolutionary path of wireless communication technologies. Several hybrid beamforming technologies are explored for millimeter-wave multiple-input multi-output (MIMO) communication. The aim is to provide a roadmap for hybrid beamforming that enhances wireless fidelity. In this systematic review, a detailed literature review of algorithms/techniques used in hybrid beamforming along with performance metrics, characteristics, limitations, as well as performance evaluations are provided to enable communication compatible with modern Wireless Intelligent Transport Systems (WITSs). Further, an in-depth analysis of the mmWave hybrid beamforming landscape is provided based on user, link, band, scattering, structure, duplex, carrier, network, applications, codebook, and reflecting intelligent surfaces to optimize system design and performance across diversified user scenarios. Furthermore, the current research trends for hybrid beamforming are provided to enable the development of advanced wireless communication systems with optimized performance and efficiency. Finally, challenges, solutions, and future research directions are provided so that this systematic review can serve as a touchstone for academics and industry professionals alike. The systematic review aims to equip researchers with a deep understanding of the current state of the art and thereby enable the development of next-generation communication in WITSs that are not only adept at coping with contemporary demands but are also future-proofed to assimilate upcoming trends and innovations.

A Survey on Maximum Ratio Combination: Applications, Evaluation and Future Directions

With the rapid development of wireless communications, the occupation of time and frequency resources becomes more crowded. The exploitation of space resources is necessary and the diversity combining techniques have substantial applications. Diversity combining achieves great diversity gains and improves the ability to combat multipath fading, among which the maximum ratio combining (MRC) performs as the optimal linear combining approach. However, MRC suffers from detrimental factors such as channel fading and no Gaussian noise in practical scenarios. In this paper, we focus on a comprehensive investigation of MRC. Starting from the MRC principle and system model, we summarize typical scenarios and analyze the channel fading statistics. For the influential factors, we further review related literature on channel correlation, cochannel interference (CCI) and impulsive noise. Major performance criteria and performance bounds are derived and compared. MRC confronts new developing challenges and the major development directions are reviewed. The paper finally discusses recent works and open problems for MRC applications and development. Emerging techniques such as artificial intelligence provide novel solutions for MRC performance improvements. The paper aims to present a summarized insight to assist readers in clarifying the analyzed methodology of MRC, so as to motivate new technology integration and extensive applications of advanced communication systems.

Ultralow-phase-noise and broadband frequency-hopping coupled optoelectronic oscillator under quiet point operation

Advancements in microwave photonics have yielded novel approaches for generating high-purity microwave sources. Among these, optoelectronic oscillators (OEOs) and coupled optoelectronic oscillators (COEOs) have demonstrated the capability to generate frequency-independent microwaves with exceptionally low phase noise. Nonetheless, the tunability of the oscillators is rather limited due to the necessity for narrowband electronic bandpass filters, presenting challenges in achieving both wide and rapid tuning capabilities. Here, we present a COEO featuring ultralow phase noise, flexible tuning capability, and high robustness. This is achieved through a quiet point (QP)-operated harmonic mode-locked fiber laser, which effectively mitigates optical amplifier noise and supermode competition, thus significantly diminishing the necessity for ultra-narrow electronic filters. Due to the liberated tuning ability, we present an oscillator that can be tuned from 2 GHz to 18 GHz, with phase noise as low as −140 dBc/Hz at 10 kHz under the QP operation. We then illustrate the practical application of the proposed oscillator in generating frequency-hopping signals with consistent spurious modes less than −85 dBc, absolute phase noise below −135 dBc/Hz at 10 kHz, hopping resolution of 1.25 MHz, and fractional frequency stability below 6.1×10−12 at 1 s averaging time when locked to a reference. The presented COEO structure emerges as a compelling solution for agile and low-noise microwave sources in advanced wireless communication and radar systems.

Improving cyber-physical-power system stability through hardware-in-loop co-simulation platform for real-time cyber attack analysis

With advancements in communication systems and measurement technologies, smart grids have become more observable and controllable, evolving into cyber-physical-power systems (CPPS). The impact of network security and secondary equipment on power system stability has become more evident. To support the existing grid toward a smart grid scenario, smart metering plays a vital role at the customer end side. Cyber-Physical systems are vulnerable to cyber-attacks and various techniques have been evolved to detect a cyber attack in the smart grid. Weighted trust-based models are suggested as one of the most effective security mechanisms. A hardware-in-loop CPPS co-simulation platform is established to facilitate the theoretical study of CPPS and the formulation of grid operation strategies. This paper examines current co-simulation platform schemes and highlights the necessity for a real-time hard-ware-in-the-loop platform to accurately simulate cyber-attack processes. This consideration takes into account the fundamental differences in modeling between power and communication systems. The architecture of the co-simulation platform based on RT-LAB and OPNET is described, including detailed modeling of the power system, communication system, and security and stability control devices. Additionally, an analysis of the latency of the co-simulation is provided. The paper focuses on modeling and implementing methods for addressing DDOS attacks and man-in-the-middle at-tacks in the communication network. The results from simulating a 7-bus system show the effectiveness and rationality of the co-simulation platform that has been designed.

Design and analysis of a microstrip antenna for superior 5G communication performance

The continuous advancement in communication systems is propelled by the growing demand for fifth-generation (5G) technology, aiming to meet the growing demands of systems that are small in size, operate at high speeds, and have a wide bandwidth. In order to address these requirements, innovative and highly efficient antenna configurations are of paramount importance. This article introduces a microstrip antenna that has been meticulously designed for optimal performance 5G systems. Optimized for 5G communication systems, the research focuses on the design and simulation of microstrip patch antennas which is shaped like butterfly, resonating at a frequency of 50.5 GHz. A Rogers RT5880 (lossy) substrate with a dielectric constant of 2.2 was employed in the antenna design. The dimensions of the proposed antennas were 6 × 6.5 × 0.787 mm³, which resulted in a geometric configuration resembling a butterfly. A comprehensive performance assessment involves exhaustive simulations using the CST Studio Suite application suite. In order to optimize critical parameters such as the Voltage Standing Wave Ratio (VSWR), reflected power, gain, frequency range (BW), and radiation pattern, the dimensions were meticulously adjusted. Significantly, the antenna operating at 50.5 GHz demonstrated a gain of 6.8 dB, in addition to a broad bandwidth of 5.364 GHz and an outstanding VSWR of 1.0131. The outcomes successfully underscore the outstanding performance exhibited by the butterfly-shaped design, thereby establishing its suitability for implementation in 5G networks.

Current Trends in Liquid Crystal Polymers and Their Applications: A Review

Liquid crystal polymers (LCPs) are now highly focused by researchers due to their improved thermal properties, mechanical strength, excellent dielectric strength, resistance to solvents, better dimensional stability, and gas barrier properties. LCPs can be used in valuable widespread applications such as energy storage, high-performance polymer fibers, actuators, information technologies, surface modification, shape memory materials, data storage, fiber optics, the medical field, electrical or electronics devices, aircraft, chemical, domestic equipment, ultra-high-strength fibers, biosensing, advanced communication systems, satellite systems, biosensing, bio-oscillators, and bioprocess monitoring. LCPs can self-assemble into different liquid crystalline phases like nematic, cholesteric, smectic, and columnar phases. The self-assembling structures of LCPs can be affected by the chemical and structural structures of the backbone of the polymeric material, nearby alkyl tails, mesogenic units, flexible spacers, etc. Depending on the mesogenic units in their molecular architecture, LCPs are basically classified into various categories, such as crosslinked, main chain, and sidechain. Again, they are also classified as cholesteric, nematic, and smectic mesophases. This paper provides a fundamental understanding, an informative overview, and details of structural aspects, properties, classification, commercial aspects, and applications of LCPs.

Next-Generation Dual Transceiver FSO Communication System for High-Speed Trains in Neom Smart City

Smart cities like Neom require efficient and reliable transportation systems to support their vision of sustainable and interconnected urban environments. High-speed trains (HSTs) play a crucial role in connecting different areas of the city and facilitating seamless mobility. However, to ensure uninterrupted communication along the rail lines, advanced communication systems are essential to expand the coverage range of each base station (BS) while reducing the handover frequency. This paper presents the dual transceiver free space optical (FSO) communication system as a solution to achieve these objectives in the operational environment of HSTs in Neom city. Our channel model incorporates log-normal (LN) and gamma–gamma (GG) distributions to represent channel impairments and atmospheric turbulence in the city. Furthermore, we integrated the siding loop model, providing valuable insights into the system in real-world scenarios. To assess the system’s performance, we formulated the received signal-to-noise ratio (SNR) of the network under assumed fading conditions. Additionally, we analyzed the system’s bit error rate (BER) analytically and through Monte Carlo simulation. A comparative analysis with reconfigurable intelligent surfaces (RIS) and relay-assisted FSO communications shows the superior coverage area and efficiency of the dual transceiver model. A significant reduction of up to 76% and 99% in the number of required BSs compared to RIS and relay, respectively, is observed. This reduction leads to fewer handovers and lower capital expenditure (CAPEX) costs.

V2V Communication in Smart Traffic Systems: Current status, challenges and future perspectives

Implementing V2V communication in intelligent traffic systems has been a topic of growing interest due to its potential to improve road safety and traffic flow. However, the widespread adoption of V2V communication in intelligent traffic systems could be enhanced by various challenges, such as infrastructure cost, security, and interoperability. These challenges must be addressed to improve the potential benefits of V2V communication. The problem statement of this study is to examine the potential benefits and challenges of V2V communication in intelligent traffic systems and provide insights into the current state of the art in V2V communication research. The proposed approach is to conduct a literature review of recent research on V2V communication in intelligent traffic systems to identify the potential benefits and challenges of V2V communication and the current state of the art in V2V communication research. The study aims to contribute to the field by comprehensively understanding the implementation of V2V communication in intelligent traffic systems and informing potential future research in this area. V2V communication can improve road safety and traffic flow in intelligent traffic systems. However, more research is needed to address the challenges and develop advanced and cost-effective V2V communication systems.

Coherent Chaotic Communication Using Generalized Runge–Kutta Method

Computer simulation of continuous chaotic systems is usually performed using numerical methods. The discretization may introduce new properties into finite-difference models compared to their continuous prototypes and can therefore lead to new types of dynamical behavior exhibited by discrete chaotic systems. It is known that one can control the dynamics of a discrete system using a special class of integration methods. One of the applications of such a phenomenon is chaos-based communication systems, which have recently attracted attention due to their high covertness and broadband transmission capability. Proper modulation of chaotic carrier signals is one of the key problems in chaos-based communication system design. It is challenging to modulate and demodulate a chaotic signal in the same way as a conventional signal due to its noise-like shape and broadband characteristics. Therefore, the development of new modulation–demodulation techniques is of great interest in the field. One possible approach here is to use adaptive numerical integration, which allows control of the properties of the finite-difference chaotic model. In this study, we describe a novel modulation technique for chaos-based communication systems based on generalized explicit second-order Runge–Kutta methods. We use a specially designed test bench to evaluate the efficiency of the proposed modulation method and compare it with state-of-the-art solutions. Experimental results show that the proposed modulation technique outperforms the conventional parametric modulation method in both coverage and noise immunity. The obtained results can be efficiently applied to the design of advanced chaos-based communication systems as well as being used to improve existing architectures.

Energy‐efficient hybrid beamforming for millimeter‐wave‐based massive multiple‐input multiple‐output system

SummaryThe advanced wireless communication system requires abridged energy consumption, enhanced data rate, and good signal coverage. The massive MIMO technology for 5G systems has been developed to accommodate several users simultaneously with superior throughput. The claim for high data rate wireless communication services is expanding quickly as time goes. Thus, the key difficulty is that as the number of users grows, the number of phase shifters grows as well, causing the system to consume more power; as a result, the system's energy efficiency decreases. Hybrid beamforming has recently emerged as an attractive technique for millimeter‐wave (mmWave) communication systems. The analog beamformer in the RF domain and digital beamformer in the baseband are coupled through a minimal number of RF chains in hybrid beamforming architecture. Hybrid beamforming utilizes fewer RF (radio frequency) chains than the total number of antennas to have a lower energy consumption design. The hybrid beamforming for a mmWave‐based massive MIMO system through different phase shifter selection mechanisms is proposed to achieve the highest energy efficiency for mmWave communications systems. The fully connected with phase shifter selection, sub‐connected with phase shifter selection (SPSS), and fully connected and sub‐connected with phase shifter selection with halved and doubled switches are considered for this research. The simulation results show the SPSS with halved switch outperforms on energy efficiency.

Effects of F− substitution on crystal structure, band characteristics and microwave dielectric properties of Li3Mg2NbO6 ceramics for high frequency applications

The structure–performance mechanism is essential to achieve comprehensive characteristics for advanced communication system. In the present work, F− ions were adopted to fabricated Li3Mg2NbO6-x/2Fx ceramics at a nitrogen atmosphere to modify dielectric characteristics. Correlation between bond characteristics, crystal structure and enhanced microwave dielectric characteristics was investigated through vibration analysis, P–V-L theory, Rietveld refinement, and First-principle calculations. Raman analysis and Rietveld refinement show that F− substitution led to a single phase. First-principle calculations indicates a high energy gap of 3.676 eV and p orbit contributed to Fermi energy. F− substitution led to the increase of Nb O bond ionicity and lattice energy, accounting for the variation in Q×f value and dielectric constant. The τf value was related to the expansion coefficient of the Li–O bond. Remarkably, the samples (x = 0.08) exhibited comprehensive dielectric characteristics with εr = 15.9, Q×f = 143,000 GHz and near-zero τf = −2.1 ppm/°C, proving an effective strategy for collaborative regulation. Based on structure simulation, 5G filter with ultra-low loss and high-suppression was designed through introducing transmission zeros from cross coupling. More specifically, a dielectric filter exhibited an interpolation loss of 0.2 dB at 3.3–3.6 GHz and high attenuations of 15 dB for 20 MHz outside the passband, verifying the feasibility for 5G applications.

Back-contact perovskite light-emitting diodes

Light-emitting diodes utilizing halide perovskites have experienced rapid advancements in recent years, demonstrating notable external quantum efficiencies. Despite these strides, the practical implementation of such devices remains constrained. In this contribution, we are dedicated to developing perovskite light-emitting diodes with a back-contact architecture using the MAPbBr3 active layer and SnO2 and Ni/NiOx back electrodes. The quantum efficiency of the fabricated devices stands at 0.015%. The operational voltage of the light-emitting diodes is characterized by its pronounced low values, attaining a maximum luminance of 70 cd/m2 at a mere 3.2 V. These results demonstrate the considerable promise of the developed back-contact perovskite light-emitting diodes for prospective applications in advanced display technologies and light communication systems.

Synthesis of CoFe2O4/mesoporous-carbon hybrid nanocomposite with enhanced microwave absorption in K and Ka-band

In the present investigation, CoFe2O4/mesoporous-carbon nanocomposites were synthesized using a facile hydrothermal method and demonstrate their dual band (K and Ka-band) microwave absorption properties, where radiation from high-resolution and close-range radars, space telescopes, and wireless point-to-point microwave communication systems populates. XRD results confirmed the pure phase formation of CoFe2O4 nanoparticles. Vibrating sample magnetometer shows a decrease in magnetization value for CoFe2O4/mesoporous-carbon nanocomposites that can be attributed to the increasing contents of non-magnetic mesoporous carbon. The reflection loss of the hybrid nanocomposite reached −31 dB at a matching thickness of 2.5 mm and effective absorption bandwidth was 4.4 GHz. The enhanced microwave absorption properties derive from the synergistic effect amid dielectric and magnetic loss of mesoporous-carbon and ferrite, respectively, and better impendence matching at their interface. In addition, the dielectric loss can be associated with polarization relaxation and mesoporous carbon conductivity and the magnetic loss arises from the natural resonance of ferrite materials. The high reflection loss and wide absorption bandwidth display that CoFe2O4/mesoporous-carbon nanocomposite having admirable microwave absorption performances can be a capable candidate for stealth technology and in advanced communication systems.

Some Properties of a Discrete Lorenz System Obtained by Variable Midpoint Method and Its Application to Chaotic Signal Modulation

Various discretization effects caused by applying numerical integration techniques to continuous chaotic systems are broadly studied in nonlinear science. Along with the negative impact on the precision of the various finite-difference schemes, such effects may have surprisingly fruitful practical applications, e.g. pseudo-random number generation, image encryption with improved diffusion and confusion properties, chaotic path planning, and many others. One such application is chaos-based communication systems which gained attention in recent decades due to their high covertness and broadband transmission capability. A crucial problem in the design of chaotic communication systems is the modulation of carrier signals. Due to the noise-like properties of chaotic signals, they can barely be modulated using the same methods as conventional harmonic signals. Thus, developing new modulation techniques is of great interest in the field of chaotic communications. In this study, we investigate the discrete model of the Lorenz oscillator obtained using controllable midpoint numerical integration and develop a novel modulation technique for chaos-based communication systems. We discover and analyze the multistability phenomenon in the dynamics of the investigated finite-difference Lorenz model through bifurcation, the basin of attraction, and Lyapunov spectrum analysis procedures. Using a specially designed testbench, we explicitly show that the proposed modulation method outperforms commonly used parametric modulation and is nearly equal to the state-of-the-art symmetry-based modulation in terms of covertness and noise resistivity. In addition, the proposed modulation technique is much easier to implement using computer arithmetics, especially in fixed-point hardware. The reported results may be efficiently applied to designing advanced chaos-based communications systems or improving the characteristics of existing communication system architectures.

Broadband wavelength conversion in Si-rich silicon nitride waveguides based on intermodal four-wave mixing

All-optical wavelength converters and frequency synthesizers represent essential components for the development of advanced and reconfigurable optical communications systems. In this respect, the exploitation of intermodal nonlinear processes in integrated multimode waveguides has received significant attention in recent years for all-optical processing applications. Here, we discuss our recent results on the realization of fully-integrated and broadband wavelength converters utilizing the Bragg scattering intermodal four-wave mixing nonlinear process in a silicon-rich silicon nitride platform.

Modeling smart electrical microgrid with demand response and storage systems for optimal operation in critical conditions

This study examines the issue in standard and operational scenarios of microgrids that arise during critical conditions. Initially, the ideal energy storage size and discharge depth are identified for optimal microgrid planning under operating conditions. Subsequently, by utilizing the energy storage system and load response, the microgrid’s vulnerability is reduced and the cost of load shedding is minimized when in critical conditions, leading to the microgrid being disconnected from the main network and operating in island mode. This model aims to analyze how the system performance is influenced by the presence of storage systems and load response programs in a numerical scenario, particularly during severe weather events. In addition, the study examines the role of advanced control algorithms and communication systems in optimizing the operation of the microgrid. By implementing smart grid technologies, the microgrid can better manage its energy resources, anticipate fluctuations in demand, and respond quickly to changing conditions. This proactive approach helps to ensure the stability and reliability of the microgrid, even in the face of unforeseen challenges. Overall, this research contributes valuable insights into the challenges and opportunities facing microgrids in both normal and emergency situations. By identifying the most effective energy storage solutions, load response strategies, renewable energy integration methods, and advanced control systems, the study aims to enhance the resilience, efficiency, and sustainability of microgrid systems in the future. The results of the proposed approach in critical operational mode represent the optimal condition of the electrical microgrid with minimum cost and load shedding considering storage systems and load response programs.

Design and analysis of a high-efficiency Tri-Band MIMO antenna for advanced communication systems

Design and analysis of a high-efficiency Tri-Band MIMO antenna for advanced communication systems