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With the development of super computation ability and invention of quantum computer, safeguarding network layer data confidentiality by computation based encryption method suffers great impact. As a result, people pay more attention to safeguarding data confidentiality in physical layer of wireless satellite communication system. In this paper, a groundbreaking method for enhancing physical layer security (PLS) by information hiding technology is proposed, that is, embedding secret information into chaotic frequency-hopping signal by multilevel frequency shift keying (MFSK) modulation. First, the secret information to be transmitted is encrypted with chaotic binary sequence. Secondly, according to frequency-hopping pattern and chaotic address sequence, select suitable modulation order and specific frequency point corresponding to each encrypted data block. Finally, the encrypted information is embedded into frequency-hopping Sine signal by MFSK modulation. Experimental results indicate that the proposed scheme is robust against various jamming attacks, such as power attenuation, noise adding, single-tone jamming, key exhaustive search, etc. [ABSTRACT FROM AUTHOR]

In this paper, a flexural Mikaelian lens in thin plate is designed by using conformation transformation. The propagation characteristics of flexural waves in the lens are investigated through rays trajectory equation, simulation analyses, and experimental tests, confirming the self-focusing properties of the Mikaelian lens. Additionally, the study explores the Talbot effect for flexural waves, revealing through simulation studies that the Talbot effect within the Mikaelian lens exhibits nearly diffraction-free properties. Building on the non-diffractive nature of the Talbot effect within the Mikaelian lens, we explore the potential for encoding flexural waves using active interference sources. The simulation and experiment results demonstrate the good performance of the designed active encoding system. This work opens up new avenues for the encoding of flexural waves, presenting promising implications for applications in communication such as structural health monitoring, wireless communication in solid media and data transmission in robotics and other areas related to flexural wave technology. [ABSTRACT FROM AUTHOR]

Summary In this article, a compact quad element coplanar waveguide (CPW) fed ultra‐wideband (UWB) multiple input multiple output (MIMO) antenna for future generation wireless communication system using a machine learning (ML) optimization approach is presented. The proposed antenna is used for 5G new radio (n46/n77/n47/n78/n48/n79), Wi‐Fi 5, Wi‐Fi 6, and dedicated short range communications (DSRC) services, vehicle to infrastructure (V2I), vehicle to vehicle (V2V), and vehicle to network (V2N) in the entire operating frequency band. It is operating from 3.2 to 11.85 GHz. The bandwidth is 8.65 GHz, and the percentage of impedance bandwidth is 115%. The comparative analysis between dual and quad elements are presented. It is optimized through the various ML model K‐nearest neighbor (KNN), extreme gradient boosting (XGB), artificial neural network (ANN), and random forest (RF). The KNN ML model achieved a higher accuracy of 93%, and it accurately predicted the S parameters of the suggested UWB antenna. The MIMO parameters are calculated and found within the acceptable limits. There is a strong correlation between the simulated and measured results. Hence, the suggested antenna is a suitable candidate for future wireless communication systems. [ABSTRACT FROM AUTHOR]

In this research, we present a 16-bit multi-mode digital-to-analog converter (DAC) with a time-interleaved (TI) structure operating at a frequency of 4 GHz over a bandwidth (BW) of 20 MHz, which is in compliance with the fifth generation (5G) wireless communications. The proposed architecture uses only one clock frequency to generate radio frequency (RF) signals and includes a second-order (2nd-order) delta-sigma modulator (DSM) with a reconfigurable low-pass (LP) mode, band-pass (BP) mode at Fs/4, and high-pass (HP) mode for signal synthesis. To increase the sampling frequency (Fs) of the TI structure, four channels are proposed, each working at a frequency of Fs/4. Since there are simple coefficients for all modes, the multiplication operation can be performed using a shifter block. This leads to design simplification, lower power consumption, smaller occupied area, and higher speed. A major challenge in designing this type of structure is the duty-cycle-error (DCE), especially in interleaved mode. In this research, we propose a new solution that solves DCE-related problems without adding digital circuits to the output of the DSM, by adjusting the analog filter circuit. Simulation results in MATLAB show that the value of signal-to-noise and distortion ratio (SNDR) in LP is equal to 106.14 dB, in BP is equal to 107.84 dB, and in HP is equal to 105.34 dB. Compensating for filters increases the spurious-free dynamic range (SFDR) to more than 118 dB. [ABSTRACT FROM AUTHOR]

Metasurface technology has attracted widespread attention, owing to its remarkable capability to control electromagnetic properties. In this paper, we design a reconfigurable reflective metasurface array operating at 5 GHz for beam generation and scanning based on coding metasurface. Field programmable gate array (FPGA) is equipped for switching the states of PIN (positive-intrinsic-negative) diodes loaded on the metasurface in real-time, resulting in a 180° phase difference. To obtain multi-beam radiation and high-accuracy beam steering, the coding sequence to produce the target radiation pattern is calculated by an algorithm program. We design the fitness function of a genetic algorithm (GA) to optimize the sequence corresponding to the target directions. The simulation result shows that with the accuracy of 1°, the proposed metasurface is capable of generating multi-beam and scanning two-dimensional beams within the 50° range. Further, we fabricate and measure a prototype sample of 15 × 15 elements, which is verified feasible by comparing the measured result and the simulation. This work demonstrates the great potential of applying this reflective metasurface to wireless communication or radar. [ABSTRACT FROM AUTHOR]

Recent applications like mmWave technologies require antenna characteristics such as high gain and wide bandwidth for smooth operation with high speed. Hence, this paper presents a novel pi‐shaped patch antenna framed within a square structure for mmWave applications at 28 GHz. In the process of designing a four‐element linear‐planar antenna array (LPAA), a thin single antenna element is designed on a 0.275 mm Rogers 5880 substrate with a dielectric constant of 2.2. The proposed single‐element antenna provides a gain of 3 dBi at 28 GHz and a wide impedance bandwidth ranging from 22.482 GHz to 40.511 GHz. Then, this proposed structure is transformed into a four‐element LPAA with a compact dimension of 0.263 mm × 18.55 mm × 23.99 mm. To enhance and predict the impedance bandwidth of the proposed LPAA, mathematical modeling using response surface methodology and constrained numerical optimization is applied. In the optimization process of the antenna, independent factors such as substrate height (Hs) and interelement spacing (d) that influence the antenna's responses such as impedance bandwidth (BW) and operating frequency (Fr) are considered. These factors are varied repeatedly and simulated using computer simulation technology (CST) suite 2019 for preparing the dataset, which is used as an input for mathematical modeling. Then, response surface methodology (RSM) is employed to relate the responses with independent factors. Models are validated using analysis of variance (ANOVA). The optimum parameters determined by applying constrained numerical optimization are substrate height (Hs) and interelement spacing (d) of values 0.263 mm and 5.61 mm, respectively. The optimized LPAA provides a wide bandwidth of 11 GHz and a peak gain of 9.25 dBi. The antenna also gives radiation efficiency of ≥98.5% and VSWR of less than 2 in its operating frequency range. The results included here are simulated using the CST EM solver and validated using the Ansys High‐Frequency Simulation Software (HFSS). The proposed antenna provides high gain and wide bandwidth, which makes it a good candidate for 5G wireless communication applications. [ABSTRACT FROM AUTHOR]

Summary: It is well known that hardware impairments (HWIs) can worthy reduce the wireless system performance at high carrier frequencies by showing random effects. Most current researches for 5 GB systems assume that transmitters and receivers (transceivers) are perfectly equipped. But wireless transceivers (TxRx) are affected by HWIs in practice. Considering the previous studies in the literature, it is reported that HWIs have devastating effects on the performance of OFDM and OFDM‐index modulation (IM) systems with fading channels. In this paper, in‐phase and quadrature phase imbalance (IQI), which is the one of most HWIs between transmitter and receiver in wireless communication systems, is examined on OFDM‐IM system over Rayleigh and Nakagami‐ m fading channels. Two well‐known detectors, the maximum likelihood (ML) detector and the log‐likelihood ratio (LLR) detector are used under the effect of the IQI at TxRx. Error performance analyzes over fading channels of the IQI effect on OFDM‐IM system are realized first theoretically and then by computer simulations. Results obtained for the presence of IQI at TxRx show that a performance evaluation based only on the presence of IQI in the receiver would be optimistic and misleading in terms of the performance of real‐life OFDM‐IM systems. [ABSTRACT FROM AUTHOR]

Summary: Developing wireless communication systems depends on reconfigurable microwave filters (MF) and dielectric resonator antenna (DRA) because the functionality of the various filters and antennas available for a wireless communication system is limited, and reconfigurable DRA and MF are utilized to overcome these limitations. The throughput of a multiantenna system can be achieved with reconfigurable DRA and filter. Various switching strategies and classifications of reconfigurable DRA and MF are presented. The electrical reconfiguration technique is most suitable for developing a reconfigurable DRA and filter among all the switching techniques. In this approach, reconfigurability may be accomplished by utilizing a PIN diode, a varactor diode, and a radio‐frequency microelectromechanical switch (RF‐MEMS). These switches are more reliable, highly efficient, and easily integrated with the microwave circuit. Reconfigurable DRA with machine learning is demonstrated. The application of reconfigurable DRA and filters in cognitive radio (CR) is also demonstrated. Also, the review article focused on the performance parameters, design, and challenges of reconfigurable antenna and MF. [ABSTRACT FROM AUTHOR]

Underwater wireless optical communication (UWOC) systems face challenges due to the significant temporal dispersion caused by the combined effects of scattering, absorption, refractive index variations, optical turbulence, and bio-optical properties. This collective impairment leads to signal distortion and degrades the optical receiver's bit error rate (BER). Optimising the receiver filter and equaliser design is crucial to enhance receiver performance. However, having an optimal design may not be sufficient to ensure that the receiver decision unit can estimate BER quickly and accurately. This study introduces a novel BER estimation strategy based on a Convolutional Neural Network (CNN) to improve the accuracy and speed of BER estimation performed by the decision unit's computational processor compared to traditional methods. Our new CNN algorithm utilises the eye diagram (ED) image processing technique. Despite the incomplete definition of the UWOC channel impulse response (CIR), the CNN model is trained to address the nonlinearity of seawater channels under varying noise conditions and increase the reliability of a given UWOC system. The results demonstrate that our CNN-based BER estimation strategy accurately predicts the corresponding signal-to-noise ratio (SNR) and enables reliable BER estimation. [ABSTRACT FROM AUTHOR]

The rapid expansion of the Industrial Internet-of-Things (IIoT) has spurred significant research interest due to the growth of security-aware, vehicular, and time-sensitive applications. Unmanned aerial vehicles (UAVs) are widely deployed within wireless communication systems to establish rapid and reliable links between users and devices, attributed to their high flexibility and maneuverability. Leveraging UAVs provides a promising solution to enhance communication system performance and effectiveness while overcoming the unprecedented challenges of stringent spectrum limitations and demanding data traffic. However, due to the dramatic increase in the number of vehicles and devices in the industrial wireless networks and limitations on UAVs' battery storage and computing resources, the adoption of energy-efficient techniques is essential to ensure sustainable system implementation and to prolong the lifetime of the network. This paper provides a comprehensive review of various disruptive methodologies for addressing energy-efficient issues in UAV-assisted industrial wireless networks. We begin by introducing the background of recent research areas from different aspects, including security-enhanced industrial networks, industrial vehicular networks, machine learning for industrial communications, and time-sensitive networks. Our review identifies key challenges from an energy efficiency perspective and evaluates relevant techniques, including resource allocation, UAV trajectory design and wireless power transfer (WPT), across various applications and scenarios. This paper thoroughly discusses the features, strengths, weaknesses, and potential of existing works. Finally, we highlight open research issues and gaps and present promising potential directions for future investigation. [ABSTRACT FROM AUTHOR]

Advancements in wireless communication and automation have revolutionized mobility systems, notably through autonomous vehicles and unmanned aerial vehicles (UAVs). UAV spatial coordinates, determined via Global Positioning System (GPS) signals, are susceptible to cyberattacks due to unencrypted and unauthenticated transmissions with GPS spoofing being a significant threat. To mitigate these vulnerabilities, intrusion detection systems (IDSs) for UAVs have been developed and enhanced using machine learning (ML) algorithms. However, Adversarial Machine Learning (AML) has introduced new risks by exploiting ML models. This study presents a UAV-IDS employing AML methodology to enhance the detection and classification of GPS spoofing attacks. The key contribution is the development of an AML detection model that significantly improves UAV system robustness and security. Our findings indicate that the model achieves a detection accuracy of 98%, demonstrating its effectiveness in managing large-scale datasets and complex tasks. This study emphasizes the importance of physical layer security for enhancing IDSs in UAVs by introducing a novel detection model centered on an adversarial training defense method and advanced deep learning techniques. [ABSTRACT FROM AUTHOR]

For the future of sixth-generation (6G) wireless communication, simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) technology is emerging as a promising solution to achieve lower power transmission and flawless coverage. To facilitate the performance analysis of RIS-assisted networks, the statistics of the sum of double random variables, i.e., the sum of the products of two random variables of the same distribution type, become vitally necessary. This paper applies the statistics of the sum of double random variables in the performance analysis of an integrated power beacon (PB) energy-harvesting (EH)-based NOMA-assisted STAR-RIS network to improve its outage probability (OP), ergodic rate, and average symbol error rate. Furthermore, the impact of imperfect successive interference cancellation (ipSIC) on system performance is also analyzed. The analysis provides the closed-form expressions of the OP and ergodic rate derived for both imperfect and perfect SIC (pSIC) cases. All analyses are supported by extensive simulation results, which help recommend optimized system parameters, including the time-switching factor, the number of reflecting elements, and the power allocation coefficients, to minimize the OP. Finally, the results demonstrate the superiority of the proposed framework compared to conventional NOMA and OMA systems. [ABSTRACT FROM AUTHOR]

In this letter, we address the problem of designing the joint waveform of radar detection, wireless communication and jamming. In the current most powerful filter‐bank multi‐carrier comb spectrum framework, a parameter‐agile time–frequency structure between symbols is elaborated to improve the uncertainty of waveform generation architecture. Furthermore, a novel composite modulation strategy that combines intra‐symbol chaos‐based radar frequency modulation and inter‐symbol chaos‐based phase modulation is proposed for a substantial jamming performance improvement. Simulation results verify that the proposed joint waveform produces a superior jamming performance while satisfying the requirements of radar detection and wireless communication. [ABSTRACT FROM AUTHOR]

Accurate jamming detection is a prerequisite and important support for efficient anti‐jamming communication in integrated sensing and communications. In recent years, the reactive follower jamming, characterized by the high jamming efficiency and the difficulty of detection, is seen as the main opponent for frequency hopping spread spectrum communication, which poses a threat to the reliability of wireless communication. Based on the background, a multiple‐nodes based cooperative jamming detection scheme is proposed for accurately detecting the reactive follower jamming. Specifically, the secondary nodes send the average energy of the suspected attacked symbols to the primary user as the uplink data in each detection period, and then the detection result is provided by the detection threshold. The optimal detection threshold is derived for the primary user according to the uplink data and channel conditions. In addition, the theoretical probability of detection under the optimal threshold is derived, and the complexity of the scheme is analysed. Simulation results show that the proposed multiple‐nodes based cooperative jamming detection scheme for reactive follower jamming can effectively improve the probability of detection. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV)-assisted communication based on automatic modulation classification (AMC) technology is considered an effective solution to improve the transmission efficiency of wireless communication systems, as it can adaptively select the most suitable modulation method according to the current communication environment. However, many existing deep learning (DL)-based AMC methods cannot be directly applied to UAV platform with limited computing power and storage space, because of the contradiction between accuracy and efficiency. This paper mainly studies the lightweight of DL-based AMC networks to improve adaptability in resource-constrained scenarios. To address this challenge, we propose an ultra-lightweight neural network (ULNN). This network incorporates a lightweight convolutional structure, attention mechanism, and cross-channel feature fusion technique. Additionally, we introduce data augmentation (DA) based on signal phase offsets during the model training process, aimed at improving the model's generalization ability and preventing overfitting. Through experimental validation on the public dataset RML2016.10 A, the ULNN we proposed achieves an average precision of 62.83% with only 8815 parameters and reaches a peak classification accuracy of 92.11% at SNR = 10 dB. The experimental results show that ULNN can achieve high recognition accuracy while keeping the model lightweight, and is suitable for UAV platform with limited resources. [ABSTRACT FROM AUTHOR]

In this paper, a complementary split ring resonator (CSRR) loaded compact CPW-fed circular shaped monopole UWB antenna with dual band notch characteristics is designed on an FR-4 substrate. The propounded band-notched UWB antenna is integrated with two frequency selective surface layers referred as bandpass frequency selective surface (FSS-1) and reflector (FSS-2) to offer enhanced radiation performance. Bandpass FSS-1 enhances the gain of the antenna by improving directivity and reflector FSS-2 reflects back the backside radiation of the proposed antenna towards the forward direction thereby increasing gain and directivity of the proposed antenna. Furthermore, a two-element orthogonal MIMO antenna is proposed with improved gain using two FSS layers. The complete configuration of the proposed two-element MIMO antenna consists of CSRR-based radiating patches, monopole ground planes and two integrated FSS layers. The proposed MIMO antenna operates in UWB range from 3.46 GHz to 16.02 GHz with dual notches at 3.9 GHz and 7.2 GHz. Isolation between MIMO elements is greater than 23 dB. Both antennas are fabricated and investigated at 5.9 GHz for vehicular communications. Maximum gain improvements of 8 dB and 6.4 dB are observed in case of the presented single element and MIMO antenna within the entire operating band due to the integration of dual FSS layers. The diversity performance of the suggested MIMO antenna is investigated by analyzing mean effective gain, envelope correlation coefficient, channel capacity loss and diversity gain parameters. The proposed MIMO antenna is a suitable candidate for vehicular and UWB wireless communication applications. [ABSTRACT FROM AUTHOR]

Data transmission is one of the critical factors in the future of the Internet of Things (IoT). The techniques of a reconfigurable intelligent surface (RIS) and backscatter communication (BackCom) are in need of a solution of realizing low-power sustainable transmission, which shows great potential in wireless communication. Hence, this paper introduces an RIS-based BackCom system, where the RIS receives energy from a base station (BS) and sends information by backscattering the signals from the BS. To maximize the sum rate of all IoT devices (IoTDs), we jointly optimized the time allocation, the RIS-reflecting phase shifts and the transmit power of the BS by exploiting an alternative optimization algorithm. The simulation results illustrate the effectiveness and the feasibility of the proposed wireless communication scheme and the proposed algorithm in IoT networks. [ABSTRACT FROM AUTHOR]

One of the significant advantages of technological evolution is the greater ease of collecting and analyzing data. Miniaturization, wireless communication protocols and IoT allow the use of sensors to collect data, with all the potential to support decision making in real time. In this paper, we describe the design and implementation of a digital solution to guide the intensity of training or physical activity, based on heart rate wearable sensors applied to participants in group sessions. Our system, featuring a unified engine that simplifies sensor management and minimizes user disruption, has been proven effective for real-time monitoring. It includes custom alerts during variable-intensity workouts, and ensures data preservation for subsequent analysis by physiologists or clinicians. This solution has been used in sessions of up to six participants and sensors up to 12 m away from the gateway device. We describe some challenges and constraints we face in collecting data from multiple and possibly different sensors simultaneously via Bluetooth Low Energy, and the approaches we follow to overcome them. We conduct an in-depth questionnaire to identify potential obstacles and drivers for system acceptance. We also discuss some possibilities for extension and improvement of our system. [ABSTRACT FROM AUTHOR]

In response to the challenge of existing wireless communication anti-jamming methods in effectively handling unknown jamming, this paper proposes a multi-parameter control anti-jamming algorithm for wireless communication systems based on the Linear–Quadratic Regulator (LQR). First, the proposed algorithm models the wireless communication system as a linear switched system based on the modulation and coding scheme. Subsequently, a feedback controller design method based on the LQR is introduced. By utilizing the multiple Lyapunov function method combined with linear matrix inequalities, sufficient criteria for the asymptotic stability of the system under unknown jamming conditions are provided. Finally, theoretical analysis and simulation results indicate that the proposed algorithm can rapidly adjust modulation and coding schemes as well as transmission power in complex jamming environments, thereby maintaining bit error rate (BER) stability and enhancing the reliability of the communication system. [ABSTRACT FROM AUTHOR]

A novel compact quad-band multiple-input-multiple-output antenna (MIMO) with high isolation is presented for universal mobile telecommunications systems (UMTS), wireless local area network (WLAN), and 5G: sub-6 GHz wireless communication applications. The proposed antenna is simulated, fabricated on low cost FR4-epoxy substrate of overall size 25 × 50 × 0.8 mm3. The proposed antenna comprises of two orthogonally placed radiators on top of substrate and ISI-shaped defected ground structure (DGS) on the bottom side. High isolation of above 20 dB is achieved with DGS and orthogonal arrangement of antenna elements. The proposed antenna is fabricated and results are tested. The measured results are well matched with simulated results. The antenna resonates at 1.98 GHz (UTMS), 2.75 GHz (WLAN), 3.37 GHz (5G/n78) and 4 GHz (5G/n77) bands with high gain and radiation efficiency. The simulated and measured results demonstrate that the proposed structure is well suitable for wireless communication applications. [ABSTRACT FROM AUTHOR]

As the demand for high-speed communication in 5G increases, this article presents a development breakthrough in millimeter-wave spectrum solutions. The focus is on designing an ultra-wideband (UWB) circular patch antenna for 5G millimeter-wave applications. To address the problem of limited bandwidth and efficiency in existing designs, a UWB antenna operating in the 20–45 GHz range with a compact form factor of 4 × 4.8 × 0.508 mm 3 has been developed. A radial basis function neural network (RBFNN) was employed to analyze and optimize the antenna's bandwidth characteristics. The resulting antenna exhibits a wide bandwidth of 25 GHz, a gain of 5.75 dB, and an impressive efficiency of 99%. To extend the capabilities of the design, a 4 × 4 MIMO antenna system was developed, incorporating four copies of the proposed UWB single antenna, achieving an extended bandwidth of 25 GHz. The MIMO system, with dimensions of 17.5 × 17.5 × 0.508 mm 3 , demonstrates excellent performance with isolation exceeding 30 dB, a gain of 6 dB, and high efficiency. Rigorous measurements validate the designs, affirming their practical viability for future 5G mmWave applications. In conclusion, the proposed UWB antenna and MIMO system offer significant advancements in 5G mmWave communication, providing high performance in bandwidth, gain, and efficiency, supported by comprehensive simulations and measurements. [ABSTRACT FROM AUTHOR]

The Non-orthogonal multiple access (NOMA) technique has drawn considerable attention as a promising solution for advanced wireless communication systems due to its higher data rates, lower latency, and high bandwidth efficiency. The decoding of NOMA signals requires standard successive interference cancellation (SIC) approaches. Due to the propagation delay and fading channels, multipath fading significantly impacts the SIC process and correct signal detection. This article proposes a hybrid approach using deep convolutional neural network-gated recurrent unit-support vector machine (CNN-GRU (CGRU)-SVM) to detect the uplink NOMA users' signals. The proposed deep learning (DL) CGRU-SVM-based receiver executes simultaneous channel estimation, equalization, and demodulation, performing perfect end-to-end operations. The simulation results discuss the bit error rate performance of the proposed CGRU-SVM-based receiver with the conventional least square and minimum mean-square error signal detection methods, along with other DL-based GRU, CNN, and CGRU approaches in uplink NOMA schemes. It provides the efficient extraction of spatiotemporal features with an SVM classifier. Moreover, the proposed model outperforms the other DL-based techniques concerning the accuracy, F1 score, and receiver operating characteristic with the area under the curve. [ABSTRACT FROM AUTHOR]

The miniaturization of antennas is crucial as it improves the integration of wireless communication system. In order to achieve miniaturization of antennas, a performance-constrained multi-objective optimization method (PCMOM) considering the size and return loss is proposed. In the PCMOM method, an optimization strategy based on a multi-port network model is introduced, enabling the formation of antennas with various structures. Furthermore, we integrate the constraint of return loss performance into the non-dominated sorting genetic algorithm II (NSGA-II), eliminating solutions that do not meet performance requirements. Three pixel antennas are designed using the PCMOM method and two of them are fabricated. Experimental results demonstrate that the proposed PCMOM method can effectively address the complex trade-off issues in antenna miniaturization design. [ABSTRACT FROM AUTHOR]

Harmonic generation and utilization are significant topics in nonlinear science. Although the progress in the microwave region has been expedited by the development of time‐modulated metasurfaces, one major issue of these devices is the strong entanglement of multiple harmonics, leading to criticism of their use in frequency‐division multiplexing (FDM) applications. Previous studies have attempted to overcome this limitation, but they suffer from designing complexity or insufficient controlling capability. Here a new space‐time‐coding metasurface (STCM) is proposed to independently and precisely synthesize not only the phases but also the amplitudes of various harmonics. This promising feature is successfully demonstrated in wireless space‐ and frequency‐division multiplexing experiments, where modulated and unmodulated signals are simultaneously transmitted via different harmonics using a shared STCM. To illustrate the advantages, binary frequency shift keying (BFSK) and quadrature phase shift keying (QPSK) modulation schemes are respectively implemented. Behind the intriguing functionality, the mechanism of the space‐time coding strategy and the analytical designing method are elaborated, which are validated numerically and experimentally. It is believed that the achievements can potentially propel the time‐vary metasurfaces in the next‐generation wireless applications. [ABSTRACT FROM AUTHOR]

The 5G communication network is a promising technology that offers user-centric connectivity to customers, enabling quick, high-capacity, and latency-free access to many applications. Software Defined Networking Controller (SDNC) is an emerging technology that is used for increasing the security and maintaining the dynamic nature of mobile devices in latency and energy-assured 5G wireless communication. Different SDN topology open flow controllers are used in the literature for increasing the throughput and security of the network but they possess some drawbacks such as frequent location update (LU) overhead, high latency, and high energy consumption. This paper proposes a hexagonal software defined network (H-SDN) controller to overcome these challenges. The proposed H-SDN topology is used to preserve Intermediate Message Layer (IML) location during multimedia data transmission. A Core Switch (CS) updates an IML's location within clusters of cells, as long as it remains within the cluster. However, in the proposed method, there will be a location update on the server if the IML departs the cluster. Experiment results show that the proposed method can increase security, which in turn increases throughput, while reduces the location update costs, energy consumption, and transmission latency. [ABSTRACT FROM AUTHOR]

Summary: A novel single‐layer ultra‐miniaturized multi‐band Frequency Selective Surface (FSS) with a circular vent is designed for shielding LTE and ISM bands. The top layer of the proposed FSS unit cell incorporates a circular patch along with convoluted arms. The designed FSS unit cell exhibits band‐rejection characteristics with a resonance of 800 MHz, 2.45 GHz, and 5 GHz and bandwidths of 523 MHz, 687 MHz, and 725 MHz, respectively. The periodicity of an ultra‐miniaturized FSS unit cell is 0.024λօ x 0.024λօ, encompassing a spatial vent hole of 0.01λօ, where λօ corresponds to the lowest operating frequency. Moreover, the proposed FSS unit cell remains unaltered angular stability up to 75° with less than 1% frequency deviation in TE and TM modes. Good polarization insensitivity for the designed four‐fold symmetrical FSS unit cell is achieved. Further, an Equivalent Circuit Model (ECM) analysis is developed to infer the physical insight of the proposed FSS unit cell. The FSS prototype is measured for the assertion, and the good agreement between the findings from simulation and measurement is validated. For real‐time assertion, the FSS prototype is verified using the Amitech SDR04. Thus, FSS is a promising candidate with good ventilation for shielding the LTE, Bluetooth, and Wi‐Fi application bands. [ABSTRACT FROM AUTHOR]

In this paper, Neodymium-doped Bismuth pyrochlore and its hybridized mixed phases (NdxBi2-xSn2O7 and Bi2O3–SnO2) were synthesized using the sol–gel autocombustion method. The synthesized material was annealed at 600 °C for three hours in a muffle furnace to ensure its crystalline structure, and X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis were conducted. Fourier Transform Infrared (FTIR) spectroscopy was employed to predict the phases and absorption frequencies. Subsequent to a comprehensive structural analysis, the dielectric properties, encompassing the real and imaginary components of Impedance, Electric modulus, dielectric constant, and tangent loss, were analyzed. This analysis spanned a frequency range from 1 MHz to 3 GHz, covering different doping concentrations. Notably, the maximum dielectric constant was attained for a doping concentration of x = 1.0 at 2.7 GHz. Conclusively, the obtained dielectric data suggest that the synthesized material holds promise for various applications, including high-frequency electronics, telecommunications, and wireless communication systems. [ABSTRACT FROM AUTHOR]

Recent advancements in optical, terahertz, and microwave systems have unveiled non-transverse optical toroidal pulses characterized by skyrmionic topologies, fractal-like singularities, space-time nonseparability, and anapole-exciting ability. Despite this, the longitudinally polarized fields of canonical toroidal pulses notably lag behind their transverse counterparts in magnitude. Interestingly, although mushroom-cloud-like toroidal vortices with strong longitudinal fields are common in nature, they remain unexplored in the realm of electromagnetics. Here, we present strongly longitudinally polarized toroidal pulses (SLPTPs), which boast a longitudinal component amplitude exceeding that of the transverse component by over tenfold. This unique polarization property endows SLPTPs with robust propagation characteristics, showcasing nondiffracting behavior. The propagation-invariant strongly longitudinally polarized field holds promise for pioneering light–matter interactions, far-field superresolution microscopy, and high-capacity wireless communication utilizing three polarizations. [ABSTRACT FROM AUTHOR]

Summary The performance of millimeter‐wave (mmWave) multiple‐input multiple‐output (MIMO) systems has been significantly enhanced by the incorporation of dynamic reconfigurable intelligent surfaces (RIS). This paper proposes a novel dynamic channel estimation technique that combines dynamic atomic norm minimization with dynamic RIS to optimize RIS‐aided mmWave MIMO systems. Leveraging the dynamic nature of both atomic norm minimization and RIS, the proposed approach efficiently adapts to changing environmental conditions, providing robust and accurate channel estimation. By dynamically optimizing the RIS configuration, the system achieves improved spectral and energy efficiency, enabling high‐speed and reliable communication in challenging mmWave environments. Theoretical analysis and simulation results demonstrate the effectiveness of the proposed dynamic channel estimation technique, highlighting its potential for enhancing the performance of future wireless communication systems. [ABSTRACT FROM AUTHOR]

Summary On‐demand manufacturing in Industry 4.0 requires flexibility of the networks which can be provided with the fifth generation (5G) of mobile communications wireless connectivity. A key component in the efficient utilization of the radio resources in a manufacturing scenario is network resource management (NRM). We show how NRM can be automated with artificial intelligence (AI). We introduce several futuristic industrial use cases that require AI in various parts of the process. We analyze the AI components' benefits and disadvantages in several deployment scenarios. The findings can be used by business stakeholders interested in deploying the 5G cellular wireless network to choose the best NRM and AI implementation strategy for a particular use case. We show that there are many viable options for the AI component in the process automation, but the cost of AI has to be considered in all cases. Also, we point out that an essential component, the standardized information flow on the status of the productivity key performance indicators (KPIs), is needed for the successful deployment and application of the 5G AI. [ABSTRACT FROM AUTHOR]

This manuscript suggests a modulation scheme for exploiting transmission diversity by integrating Alamouti coding and controlling the transmission by intelligent reflecting surface (IRS) in code division multiple access filter bank multicarrier offset quadrature amplitude modulation (CDMA-FBMC-OQAM) system, a promising technique for future-generation wireless communication. To neutralize the impact of channel phases, the IRS elements are in charge of intelligently adjusting the incident signal phases. By maximizing the signal-to-noise-ratio (SNR) of the received signal, the bit-error-rate (BER) performance is improved. By changing the number of IRS elements, taking into account various channel scenarios and modulation schemes, we compare the BER performance of the proposed system with that of the conventional Alamouti coded CDMA-FBMC-OQAM system in simulation results. The findings demonstrate that the IRS-assisted Alamouti coded CDMA-FBMC-OQAM transmission is a feasible choice for future-generation wireless communication systems. [ABSTRACT FROM AUTHOR]

Optical wireless communication (OWC) stands out as one of the most promising technologies in the sixth-generation (6G) mobile networks. The establishment of high-quality optical links between transmitters and receivers plays a crucial role in OWC performances. Here, by a compact beam splitter composed of a metasurface and a fiber array, we proposed a wide-angle (~120°) OWC optical link scheme that can parallelly support up to 144 communication users. Utilizing high-speed optical module sources and wavelength division multiplexing technique, we demonstrated each user can achieve a communication speed of 200 Gbps which enables the entire system to support ultra-high communication capacity exceeding 28 Tbps. Furthermore, utilizing the metasurface polarization multiplexing, we implemented a full range wide-angle OWC without blind area nor crosstalk among users. Our OWC scheme simultaneously possesses the advantages of high-speed, wide communication area and multi-user parallel communications, paving the way for revolutionary high-performance OWC in the future. In this work, the authors present a metasurface-based wide-angle beam splitter designed for future applications in optical wireless communication. By leveraging the metasurface polarization multiplexing and wavelength division multiplexing properties, they achieved a high-performance optical wireless communication system, possessing a Tbps communication rate, more than 120° coverage range, and up to 144 users parallel communication capabilities. [ABSTRACT FROM AUTHOR]

Integrating sweat biosensors into daily wear has the potential to effectively monitor personal lactate levels, offering the advantages of convenience, precision, and multi‐point detection. However, existing wearable fabric sweat biosensors have limitations in terms of long‐term repeatable detection and washability due to the difficulty of building a stable layer of recognition materials on the highly curved fiber surface. Here, a long‐term repeatable and washable electrochemical fabric biosensor is reported based on a fiber electrode with multi‐scaled aligned channels for efficient and reliable lactate detection. Through the functionalization of a molecularly imprinted polymer with redox‐sensitive nano reporters, the fabric biosensor exhibits impressive in situ long‐term repeatable detection for more than 400 times, washability, and stability under deformations. The multi‐scaled channels contribute to a desired electric field distribution and thus a reliable interface between the polymer and the fiber. Employing industrial sewing technology, a 20 m (L) × 0.5 m (W) sensing fabric is further produced. Ultimately, combined with a wireless communication element, the fabric biosensing system can immediately track lactate levels. [ABSTRACT FROM AUTHOR]

Integrated sensing and communications (ISAC) based on radio frequency (RF), merging the sensing and communication functionalities into a single platform, can effectively address the increasing demand for spectrums due to the proliferation of wireless devices. However, the ISAC commonly suffers from spectrum scarcity, high power consumption, and limited sensing capabilities. Here flexible self‐powered optical ISAC (O‐ISAC) is proposed and fabricated by preparing a high‐speed near‐infrared organic photodetector (NIR OPD) that exhibits a broad photodetection ranging from 300 to 1100 nm, specific detectivity over 1013 Jones, and −3 dB cutoff frequency over 1 MHz (λ = 1050 nm) in self‐powered mode, ranking as the fastest among self‐powered NIR OPDs in the region above 1000 nm. The device is fabricated by incorporating a narrow‐bandgap non‐fullerene acceptor BTPSV‐4Cl into the PCE‐10:BTPSV‐4F system to finely tune the film morphology and reduce trap states and energetic disorder. The semitransparent and regular NIR OPDs are integrated on one substrate to fabricate flexible O‐ISAC, realizing simultaneous accurate vital signs monitoring and high‐speed data transmission under ambient, sunlight, and NIR lighting conditions. It is envisioned that the proposed O‐ISAC will inspire a new generation of wireless technology to address RF limitations for emerging applications, such as intelligent healthcare, autonomous vehicles, and security. [ABSTRACT FROM AUTHOR]

Due to signal shielding caused by building structures, conventional mature positioning technologies such as the Global Positioning System (GPS) are only suitable for outdoor navigation and detection. However, there are many scenarios that urgently require high-precision indoor positioning technologies, such as indoor wireless optical communications (OWCs), navigation in large buildings, and warehouse management. Here, we proposed a millimeter-precision indoor positioning technology based on metalens-integrated camera, which determines the position of the device through imaging of beacon LEDs. Thanks to the wide-angle imaging design of our metalens, the camera can accurately capture images of beacon LEDs even when it is situated in distant corner locations. Consequently, our localization scheme achieves millimeter-level positioning accuracy across majority of wide-angle (∼120°) indoor area. Compared to traditional positioning schemes by photodiode (PD), our imaging-based approach demonstrates superior resistance to interference, thereby safeguarding positioning precision from the external signals influence. Furthermore, the compact dimensions and high performances of the positioning device make it suitable for integration into highly portable devices, such as smartphones and drones, revealing its broad potential applications in the future. [ABSTRACT FROM AUTHOR]

Threats to physical layer security from jamming attacks make wireless cognitive communication systems vulnerable. Global Positioning System signal is vulnerable to these attacks. Over the last decade, several types of jamming detection techniques have been proposed, antijamming‐based classical and machine learning (ML) techniques. Most of these techniques are inefficient in detecting jammers. Thus, there is a great need for efficient and quickest jamming detection technique‐based classifier using receiver operating characteristic (ROC) curve for different threshold values with high accuracy. In this work, we compare the efficiency of the proposed orthogonal distance (OD) and score distance (SD) method‐based robust principal component analysis (PCA) in ML classification in detecting jamming signals. Two hypotheses are proposed to distinguish between the presence and absence attack problem. Using this compressed data matrix obtained from modulated wideband converter (MWC) structure via centralized cooperation directly as input of the proposed classifier combined‐based ROC curve for real‐time detection scenarios. The performance of this proposed algorithm‐based robust PCA was evaluated and compared using the detection anomaly rate (DAR%), and false alarm rate (FAR%), area under curve (AUC), and accuracy. The performance of obtained results is good. [ABSTRACT FROM AUTHOR]

Low-density parity check (LDPC) is a channel coding technique widely utilized in the 5G New Radio standard, it is of utmost importance in facilitating proficient and secure communication in noisy environments by effectively minimizing errors during data transmission. It is primarily used in the 5G New Radio (NR) standard for encoding user information on the physical downlink shared channel (PDSCH). The necessity to satisfy the increasing expectations for throughput, latency, and dependability led to the decision to deploy LDPC codes for user data, especially in the enhanced mobile broadband (eMBB) and ultra-reliable and low-latency communications (URLLC) scenarios of 5G networks. The present system proposes the use of NR-LDPC codes to transmit data across a lognormal multipath fading channel model in the presence of AWGN. Wireless communication channels often use a lognormal multipath fading channel model, where the received signal experiences both multipath fading and lognormal shadowing. The research investigates the effectiveness of NR-LDPC coding in improving QAM-OFDM system performance by analyzing two rate-compatible base graphs and comparing their effectiveness with an uncoded system. This analysis is crucial for optimizing communication network design, especially in scenarios where the integrity of data is of utmost importance. We introduce a new method to improve the 5G NR LDPC code capability under lognormal fading conditions. This approach develops a layered min-sum (LMS) algorithm to provide enhanced error-correcting capabilities. The developed and implemented decoding algorithm represents a significant advancement over traditional detection methods. The outcomes of the simulation provide evidence of the effectiveness of the proposed NR-LDPC coding techniques in terms of their error correction and identification capabilities. In addition, the developed LMS decoding algorithm was shown to significantly decrease the BER of the system. [ABSTRACT FROM AUTHOR]

This research presents a solution in Multiple Input Multiple Output (MIMO) wireless systems to meet the growing demand for high data rates in cellular networks. Although MIMO systems offer greater capacity, the higher frequencies used have caused interference problems, especially for mobile User Equipment (UE). This research aims to reduce interference problems in the downlink of Multi-user MIMO (MU-MIMO) systems, with a specific focus on improving Quality of Service (QoS) metrics, such as outage probability and Signal-to-Interference plus Noise Ratio (SINR). Existing solutions to these challenges are complex due to the dynamic nature of the factors involved in modelling real-world scenarios. As such, an Improved Downlink MU-MIMO (ID-MU-MIMO) algorithm is developed as a solution to these problems. The ID-MU-MIMO method employs both single antenna users and multiple transmitter antennas. The performance of the suggested algorithm is compared to the IEEE 802.11ax standard specification and a previous research work for validation and evaluation. Performance measures considered to aid validation included outage probability, spectrum efficiency, and communication connection reliability. On this premise, the outcomes showed that the proposed ID-MU-MIMO scheme outperforms both the IEEE 802.11ax standard and current MD-MU-MIMO systems. In particular, compared to IEEE 802.11ax, the IDMU-MIMO technique achieved a 7.71% reduction in interference. When compared to the performance of the random and uniform MD-MU-MIMO algorithms, the proposed ID-MUMIMO scheme showed a reduction in interference in percentages of 8.90% and 2.28%, respectively. The ID-MU-MIMO scheme outpermed the random and uniform MD-MU-MIMO algorithms in terms of Signal-to-Interference Noise Ratio (SINR), outperforming them by 4.27% and 2.75%, respectively, and resource block use, outperforming them by 20.05% and 3.89%, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we analyzed Non-Orthogonal Multiple Access (NOMA) performance in the context of modern wireless cellular communications under various channel conditions. We examined different path loss models and multipath fading effects to evaluate the Bit Error Rate (BER) of NOMA. Additionally, this study was tailored for wireless communications involving multiple users in Rayleigh, Rician, AWGN, and Nakagami fading channels, all of which were considered within the framework of NOMA. To establish connections, ensure equitable user treatment, and achieve efficient spectrum utilization for multiple users across diverse channel scenarios, the Base Station (BS) adopted the NOMA technique. Furthermore, the BS employed a power allocation strategy to distribute available power among users based on their respective Power Allocation Factors (PAFs). This approach allowed users to simultaneously communicate with the BS within the same frequency range in the power domain. For users with lower PAFs, we utilized sequential interference cancellation to mitigate strong signals from other users. We validated our performance analysis using Monte-Carlo simulations, which closely aligned with the theoretical analysis. Our simulated results demonstrated that NOMA outperformed traditional Orthogonal Multiple Access (OMA) in most cases, especially in channels with various multipath fading conditions. Moreover, we observed that the effectiveness of NOMA hinged on the selection of power allocation and user pairing schemes. According to our study, NOMA exhibits significant potential to enhance the Spectral Efficiency (SE) and capacity of wireless networks in the future. We evaluated the accuracy of predicting received signal strength using various path loss models, including free space path loss, Log-normal path loss distribution, Shadowing path loss distribution, and Logdistance path loss model. In contrast to 4G networks, which are primarily affected by distancedependent path loss, 5G and beyond networks experience more significant fading effects due to their reliance on higher frequencies and wider bandwidths. [ABSTRACT FROM AUTHOR]

The terahertz spectral region, which bridges between electronics and optics, is poised to play an important role in the development of transformative wireless communication and imaging systems with unprecedented functionality. Currently, a major challenge in terahertz technology is to develop high‐performance terahertz beam‐forming devices that can dynamically shape the terahertz radiation in a flexible manner. Existing terahertz beam‐forming devices have limited coding bits, field‐of‐view, and beam gain. Here, a reconfigurable liquid crystal‐integrated terahertz metasurface is experimentally demonstrated, with each metasurface unit cell being independently addressable. The metasurface has a 260° continuous phase tuning range with a liquid crystal layer thickness of only 1% of the free‐space wavelength. The terahertz wave diffracted from the metasurface can be steered toward a wide range of directions is shown, covering a record‐large 110° field‐of‐view with a peak gain of 25 dBi. The metasurface also features a low power consumption and sub‐second switching time. Furthermore, the formation of multiple terahertz beams is demonstrated, with the direction of each beam and the power ratio between beams adjustable on demand. The proposed liquid crystal metasurface possesses compelling prospects for future terahertz communication and imaging applications. [ABSTRACT FROM AUTHOR]

Optical wireless communication (OWC) is recognized as a promising technology for future fifth generation (5G) networks. However, limited research efforts have been dedicated to the development of symmetric and bidirectional OWC systems using vertical cavity surface emitting lasers (VCSELs). In this study, we design and investigate a bidirectional 4 × 10 Gbps VCSEL-incorporated OWC system with an extensive reach, taking into account channel impairments. VCSELs offer high operating power and high reliability, making them suitable for this application. Simulation analyses have been conducted to evaluate the system performance in both the downlink and uplink directions, considering various factors such as noise, geometric losses, and attenuation losses. The results indicate that a maximum OWC range of over 130 km in the downlink direction and 128 km in the uplink direction can be achieved with a link loss of 0.001 dB. The system can tolerate a maximum link attenuation of 2.25 dB/km in the downlink direction and 2.2 dB/km in the uplink direction while maintaining a bit error rate (BER) within the acceptable limit of 10^-9. Additionally, the system demonstrates robust performance at a maximum operating temperature of 348 K for VCSELs over a 10 km range at a data rate of 40/40 Gbps. The results further indicate that the maximum values of signal, noise, gain, noise figure, and optical signal-to-noise ratio (OSNR) are − 69.68 dBm, − 87.65 dBm, − 21.14 dB, 21.14 dB, and 82.13 dB, respectively, at a total input power of − 69.61 dBm. Comparative analysis with existing studies highlights the superiority of this work over previous efforts, demonstrating significant improvements in system performance and range. This research underscores the potential of bidirectional OWC systems using VCSELs for enhancing future 5G networks. [ABSTRACT FROM AUTHOR]

The study examines how generalized Ince–Gaussian beams (gIGBs) propagate through oceanic turbulence (OT) by decomposing them into a set of Laguerre–Gaussian beams. The Huygens–Fresnel diffraction integral is utilized to derive an analytical formula representing the average intensity distribution of these beams at the output surface of the OT medium. Detailed numerical results and discussions regarding both beam and medium parameters effects on gIGBs propagation in OT are provided. These findings showcase an examination of gIGBs for underwater wireless optical communication and imaging systems, employing laser light as conduit for transmitting signals. [ABSTRACT FROM AUTHOR]

Currently, Underwater Optical Wireless Communication (UWOC) systems employing Light-Emitting Diodes (LEDs) as transmitters face significant challenges due to the absorption and scattering properties of underwater environments. This paper addresses these challenges by optimizing communication performance through a detailed link budget analysis for LED-based UWOCs. Specifically, this study focuses on selecting the optimum Lambertian order (OLO) for LED beam shaping to maximize the received optical power and minimize signal attenuation and lost light energy. The methodology involves theoretical modeling and simulation to explore various Lambertian orders within a Diffuse Line-of-Sight (D-LoS) scenario. The key parameters include the LED characteristics, underwater channel properties, and receiver parameters. This study investigated the influence of underwater channel scatterings and absorption, as well as the impact of different water types on the communication range. Additionally, various transmitter parameters (beam divergence angle, optical power) and receiver parameters (incident angle, field of view angle, PD active area) were examined. The results demonstrate the critical role of Lambertian order selection in enhancing the communication range of UWOCs. A more realistic power link budget is developed, demonstrating the impact of the optimized OLO on the received optical power. By comparing the received power with the required receiver sensitivity, this study determines the feasible communication range, providing valuable insights into improving UWOC systems. This research significantly contributes to the field by identifying the optimal Lambertian order that maximizes the received optical power while minimizing energy loss, thereby enhancing the efficiency and range of underwater optical wireless communication. [ABSTRACT FROM AUTHOR]

Optical Wireless Communication (OWC) technology, owing to its numerous merits including high-speed transmission, large modulation-bandwidth, security, and cost-effectiveness, has been considered for many applications including terrestrial links, indoor wireless transmission, underwater transmission, hybrid radio-frequency/free space optics links, and space applications. Inter-satellite OWC links are one of the most crucial applications of OWC technology, which can be used to transmit data from one part of the globe to other to achieve global connectivity. On the other hand, Orbital Angular Momentum (OAM) multiplexing is an emerging data-transmission technology used to increase the throughput and spectral-efficiency of optical links. In this work, we report, the integration of OAM multiplexing with inter-satellite OWC link to achieve high-speed information transmission for space applications. 4 OAM beams ( LG 0 0 , LG 13 0 , LG 40 0 , and LG 80 0) are used to transmit independent 20 Gbps binary data over an OWC channel between two satellites. A net transmission speed of 80 Gbps is achieved. The performance of the proposed inter-satellite WC link based on OAM transmission is evaluated through range, misalignment pointing errors, additional losses due to solar radiations, and laser transmission power using numerical simulations. The proposed system demonstrates a reliable 80 Gbps transmission over 10000 km inter-satellite link distance at 30 dBm laser power under the influence of 1.6 µrad pointing error and 5 dB additional losses with log(BER) ≤ − 5. Furthermore, as the pointing error is reduced to 1 µrad, the transmission range is increased from 10000 to 12000 km with log(BER) ≤ − 5. [ABSTRACT FROM AUTHOR]

The demand for faster and more reliable wireless communication has led to the emergence of 6G technology. One of the key features of 6G is the utilization of terahertz (THz) frequencies for data transmission, which can provide significantly higher data rates compared to previous generations. By extending the near-field sensing range, the communication distance can be increased, leading to improved coverage and performance in 6G systems. The proposed solution is achieved through the integration of metamaterials, which are artificially designed structures with unique electromagnetic properties. By incorporating metamaterials into the design of THz antennas, we can manipulate the near-field region and enhance its sensing capabilities. Near field enhancement can also be achieved through the use of reflectors, non-uniform spacing, and dielectric lenses. Plasmonic structures and chiral metamaterials are also effective. It is achieved by tailoring the electric and magnetic response of the metamaterials, which can effectively concentrate the THz radiation within the near-field region of the antenna. The proposed model reached 98.23% resolution, 92.51% sensitivity, 93.78% range, 88.58% frequency response, 94.02% directivity, 94.62% cross talk reduction. The enhanced near-field sensing range for THz antennas will have a significant impact on the performance of 6G communication systems. It will not only extend the communication distance but also improve signal quality and reduce power consumption. It will pave the way for the realization of ultra-high-speed and reliable 6G wireless communication, making it a potential game-changer in the future of telecommunications. [ABSTRACT FROM AUTHOR]

Single‐input single‐output (SISO) three‐dimensional (3D) wideband indoor directional measurements collected in a factory environment and an office environment at 38 and 70 GHz are presented. 3D single‐input multiple‐output (SIMO) dual polarised measurements with 1 × 2 antenna configurations were also carried out in a meeting room, a conference room, and an office room at the 60 GHz band. The measurements cover both azimuth and elevation by rotating the directional antenna (RDA) at the receiver side. Different statistical channel parameters such as power delay profile, power angle profile, root‐mean‐square delay spread, angular spread, and path loss were estimated for different possible antenna orientations between the transmitter and the receiver, which include line‐of‐sight, obstructed line‐of‐sight, and non‐line‐of‐sight. The polarisation effects on path loss models and the delay and angular spread models based on the surface area of the environment are studied. The results will be valuable for the design of indoor millimetre wave cellular networks. [ABSTRACT FROM AUTHOR]

The ability to distribute entanglement between quantum nodes may unlock new capabilities in the future that include teleporting information across multinode networks, higher resolution detection via entangled sensor arrays, and measurements beyond the quantum limit enabled by networked atomic clocks. These new quantum networks also hold promise for the Aerospace community in areas such as deep space exploration, improved satellite communication, and synchronizing drone swarms. Although exciting, these applications are a long way off from providing a "real-world" benefit, as they have only been theoretically explored or demonstrated in small-scale experiments. An outstanding challenge is to identify near-term use cases for quantum networks; this may be an intriguing new area of interest for the aerospace community, as the quantum networking field would benefit from more multidisciplinary collaborations. This paper introduces quantum networking, discusses the difficulties in distributing entanglement within these networks, highlights recent progress toward this endeavor, and features two current case studies on mobile quantum nodes and an entangled clock network, both of which are relevant to the aerospace community. [ABSTRACT FROM AUTHOR]

Leveraging the ultra‐wideband advantages of the terahertz band, Integrated sensing and communication (ISAC) facilitates high‐precision sensing demands in human smart home applications. ISAC channel characteristics are the basis for ISAC system design. Currently, the ISAC channel is divided into target and background channels. Existing researches primarily focus on the attributes of human target itself, e.g. radar cross‐section and micro‐Doppler effect. However, the impact of human target on neither the pathloss characteristic of background channel nor the multipath propagation characteristic of target channel is considered. To address the gap, we conduct indoor channel measurements at 105 GHz to investigate the ISAC channel characteristics with the impact of human target. Firstly, by analysing the power angular delay profiles with and without human target, the changes in quantity and power of multipath components (MPCs) are observed. Then, a parameter called power control factor is proposed to evaluate the human target impact on pathloss, thereby modifying the existing pathloss model of background channel. Eventually, the MPCs belonging to target channel are extracted within target‐oriented power delay profile to count the power proportion of each bounce MPCs of the target‐Rx link, which supports the necessity of multi‐bounce (indirect) paths modelling in target channel. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RISs) have attracted a great deal of interest due to the potential contributions to the next‐generation wireless networks. This letter proposes an enhancement to the physical layer security (PLS) of a multi‐hop RIS‐assisted underwater optical wireless communication (UOWC) system. Owing to the complexity of the underwater environment, a security‐based adaptive RIS (SA‐RIS) clustering strategy, which aims to reflect optical signals among clusters to improve the performance of the overall system, is evaluated. By combining the underwater channel model, the closed‐form expressions of probability density function (PDF) and cumulative distribution function (CDF) are derived. Moreover, by increasing the numbers of RIS clusters, the performance metrics such as secrecy outage probability (SOP) and average secrecy capacity (ASC) are evaluated under different scenarios. The obtained results demonstrated that, in contrast to the case without preventing the eavesdropper, the proposed strategy in evasion scenarios could improve the SOP significantly. It can be concluded that the system secrecy performances are further improved by assigning different RIS clusters with proper channel quality. [ABSTRACT FROM AUTHOR]

The Strauss point process is a very popular model for describing the random cellular networks, yet several key statistical properties such as intensity, empty space function, and probability generating functional have remained elusive. This article addresses these issues by first leveraging the Poisson saddle point method to approximate the distance‐conditioned intensity for Strauss point processes. Subsequently, the author derives an analytically tractable expression for the distribution of empty space distance based on a conditional thinning mechanism. Additionally, the author establishes an upper bound for the probability generating functional in Strauss point processes, which is crucial for evaluating the Laplace transform of cumulative interference in relevant cellular networks. These findings facilitate the systematic derivation of spatially averaged probability of coverage, and the accuracy of analytic results is validated through simulations. [ABSTRACT FROM AUTHOR]