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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]

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]

This paper proposes a scheme that adds XOR bit operations into the encoding and decoding process of the conventional non-orthogonal multiple access (NOMA) system to alleviate performance degradation caused by the power distribution of the original signal. Because the conventional NOMA combines and sends multiple data within limited resources, it has a higher data rate than orthogonal multiple access (OMA), at the expense of error performance. However, by using the proposed scheme, both error performance and sum rate can be improved. In the proposed scheme, the transmitter sends the original data and the redundancy data in which the exclusive OR (XOR) values of the data are compressed using the superposition coding (SC) technique. After this process, the data rate of users decreases due to redundancy data, but since the original data are sent without power allocation, the data rate of users with poor channel conditions increases compared to the conventional NOMA. As a result, the error performance and sum rate of the proposed scheme are better than those of the conventional NOMA. Additionally, we derive an exact closed-form bit error rate (BER) expression for the proposed downlink NOMA design over Rayleigh fading channels. [ABSTRACT FROM AUTHOR]

The authentication of wireless devices through physical layer attributes has attracted a fair amount of attention recently. Recent work in this area has examined various features extracted from the wireless signal to either identify a uniqueness in the channel between the transmitter–receiver pair or more robustly identify certain transmitter behaviors unique to certain devices originating from imperfect hardware manufacturing processes. In particular, the carrier frequency offset (CFO), induced due to the local oscillator mismatch between the transmitter and receiver pair, has exhibited good detection capabilities in stationary and low-mobility transmission scenarios. It is still unclear, however, how the CFO detection capability would hold up in more dynamic time-varying channels where there is a higher mobility. This paper experimentally demonstrates the identification accuracy of CFO for wireless devices in time-varying channels. To this end, a software-defined radio (SDR) testbed is deployed to collect CFO values in real environments, where real transmission and reception are conducted in a vehicular setup. The collected CFO values are used to train machine-learning (ML) classifiers to be used for device identification. While CFO exhibits good detection performance (97% accuracy) for low-mobility scenarios, it is found that higher mobility (35 miles/h) degrades (72% accuracy) the effectiveness of CFO in distinguishing between legitimate and non-legitimate transmitters. This is due to the impact of the time-varying channel on the quality of the exchanged pilot signals used for CFO detection at the receivers. [ABSTRACT FROM AUTHOR]

• The spillover transmission among sectors in China fluctuates between 55% and 90%. • Real estate acts as a net transmitter of shocks to other sectors until April 2006. • Real estate acts as a net receiver of shocks from May 2006 onwards. • Real estate transmitted shocks to the telecom services, financial, and energy sectors. • Real estate predominantly received shocks from the remaining sectors. The real estate sector in China has strong connections with other sectors. By employing forecast error variance decompositions from least absolute shrinkage and selection operator vector autoregression (LASSO-VAR) model, this study explores the real estate sector's role in China's sectoral network between January 1, 2000, and June 30, 2023. Our analysis reveals that the total sectoral connectedness ranged between 80% and 90% before 2016, but fluctuated between 55% and 90% from 2016 to June 2023. We also identify that shocks primarily spread from the real estate sector to the financial sector from 2014 to 2019. However, this pattern was reversed, with shocks spreading from the financial sector to the real estate sector from early 2020 to June 2023. Furthermore, we observe that the government's long-term mechanisms for the real estate sector have a significant impact on the connection between the real estate sector and the other sectors. [ABSTRACT FROM AUTHOR]

In this paper, we investigate interdependencies between cryptocurrencies and investor sentiment by introducing the asymmetric TVP-VAR frequency connectedness approach. Our empirical results provide evidence of pronounced and time-varying interconnectedness between sentiment and cryptocurrency. In addition, we find that negative short-term interconnectedness dominates positive short-term interconnectedness until mid-2020 when this effect was reversed, persisting until the end of the sample period. While Ripple and Bitcoin are both found to be the main net transmitters of shocks, Stellar, Ethereum, and NEM are considered net receivers of shocks. Overall, our findings suggest that market sentiment is mainly driven by cryptocurrency volatility in both the short and the long run. [ABSTRACT FROM AUTHOR]

The performance of the cognitive non-orthogonal multiple access (NOMA) systems with random locations is examined in the present paper. More precisely, the positions of the secondary receivers (SRs) are randomly distributed inside a disk with the centre at the secondary transmitter (ST). The primary networks (PNs), on the other hand, are not necessarily inside the transmission range of the ST. Two user selection schemes namely, path-loss-based and channel-gain-based approaches, are adopted to serve two SRs according to the power domain NOMA technique. Additionally, the impact of the imperfect hardware impairments (HIs) on both transmitters and receivers is also taken into consideration. Furthermore, a recently proposed transmit power allocation at the ST is employed to concurrently maximize the system performance of the secondary networks (SNs) and to strictly protect the quality-of-service (QoS) of the PNs. The correctness of the developed mathematical frameworks is corroborated by simulation results based on the Monte Carlo method. Finally, we unveil that there is no scheme that always outperforms another. Thus, an adaptive scheme can be proposed to optimize the networks' performance. Our findings also reveal that the outage probability (OP) under the harmful effect of HI can be effectively mitigated by increasing the transmit power of the ST. Additionally, increasing the transmit power of the PT is also beneficial for the SNs with the adopted transmit power allocation at the ST. [ABSTRACT FROM AUTHOR]

Cyclic interleaved frequency division multiplexing (CIFDM) stands out as a promising solution for enhancing diversity reception over frequency-selective channels. Within the CIFDM framework, cyclic interleaving at the transmitter, followed by multipath detection at the receiver, collaboratively contributes to performance improvement. A recent advancement in this domain is the introduction of CIFDM-successive interference cancellation (CIFDM-SIC) (Anuthirsha and Stuwart in ETRI J, 1--11, 2024), a multipath multistage detection method. However, CIFDM-SIC leaves room for improvement, as it only partially mitigates multipath interference resulting from the semi-orthogonality of codes in CIFDM. To address this limitation, our current approach introduces a CIFDM-decorrelative successive interference cancellation (CIFDM-dSIC) method. In the proposed CIFDM-dSIC, a decorrelation process is employed to effectively eliminate non-orthogonal interference components arising from the cross-correlation of codes in the SIC output stages. Specifically, after the completion of the entire SIC operation, interference at each output stage, except the last one, is eliminated through path-specific decorrelation of the effective spreading codes. We have conducted a comprehensive evaluation of the performance of CIFDM-dSIC under various scenarios, comparing it with both existing CIFDM and traditional interleaved frequency division multiplexing methods. Simulation results unequivocally establish the dominance of the proposed CIFDM-dSIC, affirming its reliability in terms of bit error rate and diversity reception. [ABSTRACT FROM AUTHOR]

Multiple independent outputs are highly desirable to power the different ports in some power distribution wireless power transfer (WPT) systems. This paper develops a WPT system with one transmitter coil and one multi‐tap‐receiver coil to generate multiple independent output voltages. The systems with dual‐tap‐receiver, three‐tap‐receiver, and multiple‐tap‐receiver are analyzed in theory. Because the sub‐windings of the multi‐tap‐receiver can be reused in positive series, the wire length of the receiver (WLR) is reduced compared to the system with multi‐independent receivers. For instance, a multiple outputs system needs N voltage levels (v1, v2, …, vN) while the receiver has N sub‐windings (LS1, LS2, …, LSN), then the voltage level vi (1 ≤ i ≤ N) is powered by sub‐windings LS1, LS2, …, LSi. Hence, the highest voltage level is fed with the entire charge included in the whole receiver, and a part of the sub‐windings supplies low‐voltage levels. The proposed system reduces WLR by more than 32.77% while v2/v1 is 2:1, and under the condition that v3/v2/v1 is 3:2:1, the saved WLR is higher than 75.73%. Besides, an 880‐W prototype with a dual‐tap receiver is built. The experimental results verify that the dual output voltages are load‐independent and non‐interfering. The efficiency is higher than 93.259%. [ABSTRACT FROM AUTHOR]

The purpose of this research is to investigate the differences in specific GPS variables related to the running performance of amateur football players, comparing data over 15 min periods of time throughout the match, as well as examining differences between players of different positions. The participants are adult male amateur football players from the same team. The analysis of the players' performance was carried out using GPS transmitters over twelve league matches (Amateur Division A) for all starting players (except the goalkeeper) who completed the match without being substituted. The formation was 1-4-3-3, and the players were divided into five categories: Central Defenders (CDs), Full Backs (FBs), Central Midfielders (CMs), Wingers (Ws), and Center Forwards (FWs). Each match was divided into two halves and into periods of fifteen minutes. The analysis concerns the total distance covered within these time periods and in different speed zones. The results showed that CDs covered the shortest distance (p < 0.05), while CMs and Ws covered the longest (p < 0.05) in the most of the 15 min time periods. In both halves, it was observed that players covered greater distances at low intensity in the last 15-min periods. Finally, the total distance covered at low intensity was greater in the last 15-min period of the 2nd half compared to that of the 1st half. As footballers' loads vary based on their playing position, the data from this study warrant extensive consideration for better training planning. [ABSTRACT FROM AUTHOR]

Objective Analyzing the applicability of pipeline simulation technology in energy measurement, and examine the deviation between simulation calculation results and actual pipeline measurement values. Methods Using a closed natural gas pipeline network with multiple gas sources will be as an example, a simulation model with functions for natural gas heat generation, pressure, and flow calculation was established. This model is based on the theoretical foundation of pipeline network simulation for energy measurement. Results The deviation between the simulation results of heat generation and the calculated values of the on-site chromatographic analyzer is within 0.3%, which meets the requirements of the maximum allowable error of assigned heat generation in GB/T 18603—2023 Technical requirement of measuring systems for natural gas. The deviation between the pressure simulation calculation result and the recorded value of the on-site pressure transmitter is within 1.0%, and the deviation between the flow simulation calculation result and the measured value of the on-site flow meter is within 2.0%. Conclusions The energy measurement technology based on pipeline simulation is a feasible method for assigning heat generation values to complex multi-gas source pipelines. This method can also be used for real-time tracking or verification of pipeline pressure, flow rate, and natural gas pipeline inventory. [ABSTRACT FROM AUTHOR]

Summary In this paper, a non‐orthogonal multiple access (NOMA)‐based precoded quadrature spatial modulation (PQSM) technique (NOMA‐PQSM) has been proposed for the downlink scenario. In NOMA‐PQSM, two intended receiving antennas are activated at any time instant. One antenna is activated for the in‐phase component of the transmitted signal, and another one is activated for the quadrature phase component, on the basis of data bits. NOMA‐PQSM provides benefits like improved spatial diversity and spectral efficiency in comparison with spatial modulation. This work uses zero forcing (ZF) precoding over downlink flat fading Rayleigh multiple input multiple output (MIMO) channels, to limit the channel's deteriorating effect on transmitted signal, assuming perfect channel state information (CSI) at the transmitter. A low complexity receiver based on the successive interference cancellation is used. An expression for the upper bound of average bit error probability is derived. Moreover, the expressions for the sum mutual information of users and its lower bound are also derived. The proposed scheme is compared with the preprocessing aided spatial modulation (PSM)‐based counterpart. Monte Carlo simulations reveal that the NOMA‐PQSM scheme outperforms its orthogonal counterpart and the PSM scheme. [ABSTRACT FROM AUTHOR]

Summary: Frequency‐domain detection stands as a critical method in remote geophysical exploration; however, its practical application is constrained by the considerable size of the requisite instrumentation. In this paper, we present a compact frequency domain electromagnetic detection system. The integration of intelligent power devices and a novel hardware architecture substantially diminishes the system's dimensions, thereby enhancing its portability. Furthermore, the system design incorporates sinusoidal pulse width modulation and digital phase‐locked amplification to ensure the efficacy of the proposed system. Both the transmitter and receiver system are constrained to dimensions smaller than 1.5 m. Subsequent experimental validation attests to the exemplary hardware performance of the proposed system, with the transmitting voltage of the transmitter circuit attaining 500 V, and the receiver circuit exhibiting a sensitivity as low as 10−8 V. Significantly, this design paradigm not only facilitates the integration of transmitter and receiver systems for frequency‐domain electromagnetic detection but also introduces novel prospects for the application of frequency‐domain electromagnetic detection methods across diverse fields. [ABSTRACT FROM AUTHOR]

The anti-sorting transmission is one of the primary RF stealth signals, as well as radio frequency (RF) stealth is one of the greatest significant study areas in radar stealth technology. This study first examines the anti-sorting signal's design basis. Next, it is suggested to use a quadratic stochastic appropriate algorithm on the cosine exponent. Furthermore, utilizing the suggested nonlinear chaotic mapping, a more unpredictable wide-interval PRI signals is created while taking the sorting individual's allowable limits into account. Finally, evaluations of intricacy, equilibrium, and unpredictability confirm the effectiveness of the suggested chaotic mapping. The transmitter capacity for anti-sorting is then modeled. The outcomes demonstrate the intended signal's strong anti-sorting capabilities. [ABSTRACT FROM AUTHOR]

Light‐emitting diodes and photodiodes, often acting as transmitters and receivers, are two key optical components for constructing an optical communication system. Recently, solar‐blind optical wireless communication (SB‐OWC) has emerged as a promising free‐space communication platform due to its unique advantages, including low background noise, high security, and non‐line‐of‐sight ability. However, the development of deep ultraviolet (DUV) emitters and detectors is still in its early stages with relatively low efficiency and poor detection capability, which hampers the further progress of SB‐OWC. Herein, a triangular‐shaped micro‐sized diode (T‐μ‐diode) is reported that can significantly boost its DUV emission and detection performance compared with a regular circular‐shaped micro‐diode (C‐μ‐diode) due to improved current injection and enhanced light extraction/absorption behavior. Specifically, the T‐μ‐diodes demonstrate superior light output power with a −3 dB modulation bandwidth over 566 MHz operating at an extremely high current density of 2 kA cm−2 while possessing a higher photo‐responsivity of ≈160 mA W−1 with a faster response speed of 5.1 ns, surpassing the traditional C‐μ‐diodes in both light emitting and detecting modes. Importantly, a bidirectional on‐chip data transmission system is realized by simply switching the operation mode of two T‐μ‐diodes monolithically fabricated on the same platform with boosted emission and detection functionalities. [ABSTRACT FROM AUTHOR]

The bit error rate (BER) in relation to the signal-to-noise ratio (SNR) serves as a widely recognized metric for assessing the performance of communication systems. The concept of SNR is so integral that many existing studies presume its definition to be understood, often omitting the specifics of its calculation in their simulations. Notably, the computation of SNR from the perspective of the transmitter yields distinct behaviors and outcomes compared to that from the receiver's side, particularly when the channel encompasses more than mere noise. Typically, research papers utilize the transmitter-side (or ensemble-average) SNR to benchmark the BER performance across various methodologies. Conversely, the receiver-side (or short-term) SNR becomes pertinent when prioritizing the receiver's performance. In the context of simulating the long-term evolution (LTE) downlink, applying both SNR calculation approaches reveals that the receiver-side SNR not only produces a significantly lower BER compared to the transmitter-side SNR but also alters the relative BER performance rankings among the channel models tested. It is deduced that while the transmitter-side SNR is apt for broad performance comparisons, it falls short in thoroughly examining the BER behavior of a receiver across varying SNR scenarios. Therefore, the transmitter-side SNR is useful when comparing the performance of the simulated system with other studies. Conversely, if the primary concern is the actual BER performance of the receiver, the receiver-side SNR could provide a more accurate performance assessment. [ABSTRACT FROM AUTHOR]

Background: Depression is known as the "mental cold" and is also considered a major cause of disability worldwide. It is estimated that over 300 million people worldwide suffer from severe depression, equivalent to 4.4% of the world's population. The monoamine hypothesis of depression predicts the underlying pathophysiological mechanisms of depression, but in‐depth research has failed to find convincing evidence. Method: In this study, we will dynamically and strictly quantitatively monitor the concentration changes of monoamine transmitters in the cerebrospinal fluid (CSF) of macaques, based on our previous work. In the experiment, timed and quantitative collection of CSF samples from macaques was performed and the concentration of monoamine transmitters was determined. Result: The results showed that after 2 months of chronic stress, the concentrations of high vanillin acid (HVA) and 3,4‐dihydroxy‐phenylacetic acid were significantly higher in the maternal separation (MS) group, whereas there was no significant difference in dopamine and 5‐hydroxyindoleacetic acid. Conclusion: This study is the first to observe the long‐term dynamic relationship between early adversity, chronic stress, adolescent depression, and CSF monoamine concentrations. The research suggests that MS and chronic stress play an undeniable role in the pathogenesis of depression and that concentrations of HVA and dihydroxyphenylacetic acid are likely to serve as early markers of depressive‐like symptoms in macaques. [ABSTRACT FROM AUTHOR]

Intelligent Reflecting Surfaces (IRSs) enable us to have a reconfigurable reflecting surface that can efficiently deflect the transmitted signal toward the receiver. The initial step in the IRS usually involves estimating the channel between a fixed transmitter and a stationary receiver. After estimating the channel, the problem of finding the most optimal IRS configuration is non-convex, and involves a huge search in the solution space. In this work, we propose a novel and customized technique which efficiently estimates the channel and configures the IRS with fixed transmit power, restricting the IRS coefficients to  { 1 , − 1 } . The results from our approach are numerically compared with existing optimization techniques.The key features of the linear system model under consideration include a Reconfigurable Intelligent Surface (RIS) setup consisting of 4096 RIS elements arranged in a 64 × 64 element array; the distance from RIS to the access point measures 107 m. NLOS users are located around 40 m away from the RIS element and 100 m from the access point. The estimated variance of noise  N C  is 3.1614  ×   10 − 20 . The proposed algorithm provides an overall data rate of 126.89 (MBits/s) for Line of Sight and 66.093 (MBits/s) for Non Line of Sight (NLOS) wireless communication. [ABSTRACT FROM AUTHOR]

Inter-satellite optical wireless communication (IsOWC) is frequently utilized for fast data transmission between various far away satellites in free space. Thousands of users are connected via broad-area applications that use network topologies with many frequencies per optical fiber and a range of transmission rates and capacities. Multiple frequencies being transmitted simultaneously on a fiber having a nanometer range (1300–1600) that is a powerful feature of an optical communications link. When coupled with optical amplifiers, the WDM idea creates communication lines that provide rapid user-to-user communication throughout national borders. A well-known drawback of free space optics (FSO) or Inter-Satellite Link (ISL) is degradation in optical signal power, in addition to its appealing advantages. The traditional system is improved in order to solve this issue. Using the optisystem-15 simulator, we analyzed the IsOWC link's capability for fast data transfer based on subjective factors including received power, Q-factor and BER. 16-channels multiplexed with modulation technique transmitters to the system are explained by the projected model. The link has been used at various data rates, distances, and external Match-Zehnder modulation. Applied a series hybrid optical amplifier of erbium-doped fiber amplifier (EDFA) and a laser amplifier that exists prior to and after the OWC line with the given parameters. Different OWC ranges with a loop control of 3 loops that made total link length 1600 km, and searching different data rates to show their impact on system efficiency, which showed a great enhancement in results that are crucial to the current inter-satellite OWC link. [ABSTRACT FROM AUTHOR]

This study presents an innovative wirelessly powered stent rectenna system for endovascular aneurysm repair (EVAR), targeting abdominal aortic aneurysm (AAA) treatment. The system includes an on‐body flexible transmitter (Tx) antenna and an in‐body rectifier‐integrated stent receiver (Rx) antenna, operating in the industrial, scientific, and medical (ISM) band of 868 MHz. The Rx stent antenna, made from a biocompatible nylon‐coated metallic wire, ensures mechanical stretchability, biocompatibility, and precise current distribution. The flexible Tx antenna is designed for wearable use. A miniaturized rectifier on flexible polyimide, coated with biocompatible polydimethylsiloxane, converts received power into DC energy. The EVAR stent system's performance is validated through measurements using a saline‐filled American Society for Testing and Materials (ASTM) phantom. Magnetic resonance imaging (MRI) compatibility studies using Sim4Life simulations assess potential heating and image artifacts, confirming the proposed stent's MRI suitability. Wireless power transfer experiments demonstrate reliable power delivery to the Rx in various real‐world scenarios, achieving a power transfer efficiency of 3.6% at 18 cm inside the phantom. The flexible rectifier shows a peak efficiency of 87% at 15 dBm input power. The proposed system's exceptional performance and efficiency highlight its potential for effectively wirelessly powering advanced AAA stents. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligence surface (RIS) consists of a large number of low-cost passive reflecting elements has attracted significant attention from communication communities, which is mainly due to its ability to substantially improve the communication performance. In light of this, we develop a three-dimensional geometry-based multiple-input multiple-output propagation model in this article, which is mainly suitable for describing the high-speed railway communications assisted by RIS in macrocell environments, such as train-to-train scenarios. In such propagation model, the waves emitted from the mobile transmitter experience non line of sight propagation links before reaching the mobile receiver, as well as the RIS propagation links before reaching the receiver. We compute the expressions of the RIS-assisted high-speed railway channel propagation properties, for example, spatial-time cross-correlation functions, between different propagation links. Then, we study the temporal autocorrelation functions of the propagation links in the provided propagation model for distinct movement time instants. Analysis shows that the communication performance can be enhanced by rising the number and the size of RIS reflecting elements, and it is validated by numerical simulation results. [ABSTRACT FROM AUTHOR]

With the growing demand for positioning services, angle-of-arrival (AoA) estimation or direction-finding (DF) has been widely investigated for applications in fifth-generation (5G) technologies. Many existing AoA estimation algorithms only require the measurement of the direction of the incident wave at the transmitter to obtain correct results. However, for most cellular systems, such as Bluetooth indoor positioning systems, due to multipath and non-line-of-sight (NLOS) propagation, indoor positioning accuracy is severely affected. In this paper, a comprehensive algorithm that combines radio measurements from Bluetooth AoA local navigation systems with indoor position estimates is investigated, which is obtained using particle filtering. This algorithm allows us to explore new optimized methods to reduce estimation errors in indoor positioning. First, particle filtering is used to predict the rough position of a moving target. Then, an algorithm with robust beam weighting is used to estimate the AoA of the multipath components. Based on this, a system of pseudo-linear equations for target positioning based on the probabilistic framework of PF and AoA measurement is derived. Theoretical analysis and simulation results show that the algorithm can improve the positioning accuracy by approximately 25.7% on average. [ABSTRACT FROM AUTHOR]

In response to the problems of communication capacity and spectrum resource constraints, radio over fiber (ROF) technology has gained widespread adoption, and the quality and performance of the optical transmitter module also directly affect the transmission of the link. This paper presents the design of a direct modulation optical transmitter module in the frequency band ranging from 2.6 kHz to 206.8 MHz using OPA690 broadband voltage feedback op‐amp. The module features a tunable bias voltage range from 0 to 5 V to accommodate different threshold voltages for modulation power supply. It offers a gain of 12 dB and a signal‐to‐noise ratio exceeding 50 dB while demonstrating excellent stability, high signal purity, good spectral response characteristics, and compact size advantages. Based on this design, we further optimized the system circuit by adding a fourth‐order Butterworth filter structure, reducing the lower cut‐off frequency to about 500 Hz, increasing the gain by 6 dB, reducing the return loss to −26.91 dB, and the module's signal‐to‐noise ratio exceeding 90 dB. This optimization scheme improves the stability and signal purity of the optical transmitter module and improves the spectral response characteristics. In this paper, Multisim is used to analyze and verify the proposed optical transmitter circuit. In addition, a complete link experiment was carried out using an optical receiving module designed in the same laboratory to verify the feasibility of our proposed module. [ABSTRACT FROM AUTHOR]

The semi-airborne electromagnetic method (SAEM) has recently gained increased interest in geophysical exploration applications. For SAEM, ground-based transmitters are deployed within the area of interest or in its vicinity, and the induced magnetic is measured airborne. Because of the large footprint of extended transmitters, three-dimensional (3D) effects can have a significant impact on the gathered data and 3D modelling and inversion approaches must be employed for data analysis. Any 3D EM simulation is a resource-consuming task and efficient tools can therefore be useful to add data interpretation. In this study, 3D tomographic inversion of frequency-domain SAEM data was accomplished based on the integral equation (IE) method. The inversion was linearised by approximating the sensitivity matrix. We further employ the quasi-linear approximation to facilitate out quick forward modelling in the inversion which is tractable on field computers. While this approach sacrifices inversion accuracy for efficiency, we guide the inversion by introducing multinary constraints. These constraints impose a priori known conductivity values into the inversion process. Our results from synthetic and field data demonstrate the efficiency of our approach in achieving a coherent geophysical model that is consistent with geological data and findings from other geophysical techniques. This method provides a practical and capable solution for unveiling conductive 3D structures in the field. [ABSTRACT FROM AUTHOR]

Low-frequency electromagnetic induction (EMI) is a non-invasive geophysical method that is based on the induction of electromagnetic (EM) waves into the subsurface to quantify changes in electrical conductivity. In this study, we present an open (design details and software are accessible) and modular system for the collection of EMI data. The instrument proposed allows for the separations between the transmitter to be adjusted and up to four receiving antennas as well as the acquisition frequency (in the range between 3 and 50 kHz) to permit measurements with variable depth of investigation. The sensor provides access to raw data and the software described in this study allows control of the signal processing chain. The design specifications permit apparent conductivity measurements in the range of between 1 mS/m and 1000 mS/m, with a resolution of 1.0 mS/m and with a sampling rate of up to 10 samples per second. The sensor allows for a synchronous acquisition of a time stamp and a location stamp for each data sample. The sensor has a mass of less than 5 kg, is portable and suitable for one-person operation, provides 4 h of operation time on one battery charge, and provides sufficient rigidity for practical field operations. [ABSTRACT FROM AUTHOR]

To enhance the sensitivity, signal-to-noise ratio and durance of electrospray mass spectrometer, an off-axis ion guide combining a traveling-wave (TW) stacked-ring and a shaped ion funnel has been designed, which is capable of filtering out the neutral contaminants and charged droplets entrained in the electrospray plume. According to its structural characteristics, the corresponding TW and radio frequency (RF) coupling power supply and measurement as well as control system were designed. Customizable Ethernet communication protocol was used to control the field-programmable logic gate array (FPGA) for full-circuit signal control and generation, and an 8-channel traveling-wave amplitude monitoring was achieved through a 12-bit analog-to-digital converter (ADC) and a 16-bit digital-to-analog converter (DAC). In addition, dual-plane transformer coupling circuit was designed. The use of traveling wave changed the central reference frame of the RF, achieving the purpose of programmed RF and the effect of TW in the stacked-ring to provide axial kinetic energy. The stability and accuracy of the electrical parameters of the hardware system on the off-axis transmission structure were tested. The results showed that the controllable voltage range of TW power supply is 0.1-100 V and the controlled DC power supply’s full range detection and control absolute error are less than 0.04 V. The frequency of TW up to 400 kHz, both rising edge and falling edge are less than 30 ns. Furthermore, the waveforms of TW, RF and post-coupling waveform are sufficiently smooth. The test results also showed that the performance of the power supply and measurement and control system are stable and reliable, and their accuracy and range can satisfy the design requirements. Then, the performance of off-axis structure was tested under rough vacuum using reserpine ions. It was found that the reference voltage difference between the upper and lower traveling-waves (the voltage which the ions were extracted), the voltage of the upper traveling-waves, and the traveling-wave duty cycle of the off-axis ion transmitter have more significant effects on the off-axis transmission of ions than other electrical parameters. The experimental results provide a fundamental understanding of ion transport and off-axis separation of traveling-wave stacked-ring structures, which is valuable for the development of high signal-to-noise mass spectrometry system. In the future, this novel traveling-wave off-axis transmitter and its coupling power supply system will be applied to homemade mass spectrometry instruments. Besides, we will compare the developed device with the mainstream ion transmission devices in the market so as to further improve the device structure and power supply parameters, and deeply explore the role of traveling-wave off-axis transmitter in different ionization sources and different detectors. [ABSTRACT FROM AUTHOR]

Wireless charging technology provides a convenient and safe method for electric vehicles. To meet the needs of commercial operations, it is essential to accurately measure the active power at the transmitter end of the wireless charging system. However, due to the high-frequency and high-voltage, measuring the voltage at the transmitting coil is challenging. In response to this issue, this paper focuses on the bilateral LCC compensation network and analyzes the harmonic components of the current and voltage at transmitting coil. It derives the voltage relationship between compensation capacitor and the transmitting coil and indirectly measure voltage at transmitting coil, finally proposing an active power calculation method for the transmitting coil. An experimental prototype of a wireless charging system utilizing bilateral LCC compensation is built. Simulations and experiments verify that the active power consumed by the transmitting coil is mainly the fundamental component, and the impact of the sampling frequencies and power levels on the measurement accuracy is discussed. [ABSTRACT FROM AUTHOR]

A quantum conference key agreement (QCKA) protocol based on differential-phase-shift quantum key distribution is presented, which provides a common secret key for secure communication between more than two parties. In the proposed protocol, one party simultaneously broadcasts a weak coherent pulse train with {0, π} phases to multiple parties that measure the phase differences between adjacent pulses using a delay interferometer followed by photon detectors, and the transmitter and receivers share secret key bits from the coincident counts in the receivers. The system setup and operation are simpler than those of conventional QCKA schemes that use a multipartite quantum entanglement state. The key creation performance is evaluated by considering the eavesdropping probability. The results indicate that the proposed scheme offers better performance than the conventional entanglement-based QCKA system. [ABSTRACT FROM AUTHOR]

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Multiple-input multiple-output (MIMO) technologies use multiple antennas at the sender and the receiver to get the high data rate that the next-generation communication system needs. This paper compares MIMO systems using the Quadrature Phase Shift Keying (QPSK) modulation scheme for two-channel distributions of Rayleigh and Weibull types. The performance of the work is far with the Minimum Mean Square Equalizer (MMSE) in terms of Bit Error Rate (BER) for various antenna number situations on the transmitter and receiver sides. The MIMO module is carried out using MATLAB code. The channel noise will be a signal of random noise that is generated. To mitigate the impact of interchannel interference, the MMSE approach employs inverse filtering at the receiver, and BER will be calculated. According to simulation results, the system's performance is primarily influenced by the number of antennas; it decreased as the number of antennas increased, and the BER of the Weibull channel decreased as the two-parameter value increased. [ABSTRACT FROM AUTHOR]

Continuous variable measurement-device-independent quantum key distribution (CV-MDI-QKD) removes all known or unknown side-channel attacks on detectors. However, it is difficult to fully implement assumptions in the security demonstration model, which leads to potential security vulnerabilities inevitably existing in the practical system. In this paper, we explore the impact of imbalanced modulation at transmitters on the security of the CV-MDI-QKD system mainly using a coherent state and squeezed state under symmetric and asymmetric distances. Assuming two different modulation topologies of senders, we propose a generalized theoretical scheme and evaluate the key parameter achievable of the protocol with the mechanism of imbalanced modulation. The presented results show that imbalanced modulation can achieve a relatively nonlinearly higher secret key rate and transmission distances than the previous protocol which is the balanced modulation variance used by transmitters. The advantage of imbalanced modulation is demonstrated for the system key parameter estimation using numerical simulation under different situations. In addition, the consequences indicate the importance of imbalanced modulation on the performance of CV-MDI-QKD protocol and provide a theoretical framework for experimental implementation as well as the optimal modulated mode. [ABSTRACT FROM AUTHOR]

Due to the presence of numerous branches in the pressurized water pipeline network (PWPN), leak-caused negative pressure wave (NPW) has non-unique propagation path, so leak detection and positioning for PWPN is highly challenging. This paper proposes a leak monitoring and positioning method for PWPN based on the time delay matching of NPW propagation. Via introducing the NPW velocity equation, the PWPN is divided into short segments with equal NPW propagation duration, and then the shortest NPW propagation path from each discrete point, namely hypothetical leak point, to each deployed pressure transmitter, is efficiently numerically searched and then used to calculate the NPW arrival time and establish a contrastive time delay library (CTDL) in advance. A set of signal processing algorithm are developed to capture the NPW arrival time and compare these measured values with the pre-established CTDL to accurately position leak point in the PWPN. The effectiveness of this method is verified via leak localization experiments on a field PWPN with an area of 12 × 12 km and 1478 branches. The proposed method can achieve leak positioning with errors less than 100 m throughout the entire pipeline network when only six pressure transmitters are effective. [ABSTRACT FROM AUTHOR]

The performance of multi-hop cluster-based wireless networks under multiple eavesdroppers is investigated in the present work. More precisely, we derive the outage probability (OP) of the considered networks under two relay selection schemes: the channel-gain-based scheme and the random scheme. Although equally correlated Rayleigh fading is taken into consideration, the derived mathematical framework remains tractable. Specifically, we represent the exact expression of the OP under the channel-based scheme in series form, while the OP under the random scheme is computed in a closed-form expression. Additionally, we propose a novel power allocation for each transmitter that strictly satisfies the given intercept probability. Numerical results based on the Monte Carlo method are provided to verify the correctness of the derived framework. These results are also used to identify the influences of various parameters, such as the number of clusters, the number of relays per cluster, and the transmit power. [ABSTRACT FROM AUTHOR]

For underwater blue–green light multiple-input multiple-output orthogonal frequency division multiplexing modulation system (MIMO-OFDM), the underwater MIMO channel gain matrix corresponding to the change of receiver spacing was analyzed and derived, and a proportional power allocation scheme combined with singular value decomposition (SVD) precoding was proposed, in order to eliminate inter-channel interferences of the MIMO system. The simulation results show that when the transmitter spacing is fixed, and the receivers adopt the same spacing as the transmitters, which is difficult to achieve in the complex underwater environment, the system bit error rate (BER) performance under the proposed proportional power allocation scheme is the same as that of the average power allocation. When the receiver spacing increases, the system BER under the proposed scheme can ensure better overall performance compared with that of the traditional average allocation scheme. [ABSTRACT FROM AUTHOR]

The analysis of average spectral efficiency (ASE) of multi-pulse position modulation (MPPM) scheme with optimal rate adaptation (ORA) and channel inversion with fixed rate (CIFR) adaptation schemes over the gamma–gamma free space optical (FSO) channel has been carried out in this paper. The performance of the adaptation schemes has been analyzed in terms of the average channel capacity and has been further scrutinized under the aperture averaging effects in moderate and strong atmospheric turbulence. For the first time, closed form expressions for MPPM with ORA and CIFR transmitter adaptation schemes have been derived in terms of Meijer's G functions. Using the derived expressions, the performance of the two adaptation policies have been compared for different transmitter power and varying FSO length, MPPM modulation order and aperture averaging. The analysis results revealed that generally, ORA performs better than CIFR under the considered turbulence strength, modulation order and aperture averaging. However, aperture averaging offers more gain in ASE in strong turbulence than moderate turbulence for both ORA and CIFR. Furthermore, the results revealed that aperture averaging effects offers much more gain in ASE when used with CIFR than ORA. [ABSTRACT FROM AUTHOR]

Modern small satellite development represents a new trend, a new design idea, and it can be used as a transmitter to assist helicopter monitoring. The imaging model of the arc array bistatic SAR with a small satellite transmitter is studied. Due to the long resident time of small satellite platform and the wide-area observation capability of arc antenna, it has a wide application prospect in the field of earth detection and remote sensing. However, the motion state of the small satellite and the special scanning mode of the arc antenna have some effects on the SAR imaging results. Therefore, the imaging geometry of the arc array bistatic SAR with a small satellite transmitter is established, and an improved Chirp Scaling imaging algorithm is proposed. Firstly, the motion compensation function is used to compensate the migration caused by the high-speed motion of the small satellite. Then, the two-dimensional spectrum is derived by using standing phase principle and scaling function. Next, the coupling between range and azimuth is compensated by consistent range migration correction and secondary range compression, and residual phase is compensated in azimuth frequency domain. Finally, simulation results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

To enhance the information security in multiple input multiple output (MIMO) wireless communication systems, nonlinear transmission is studied in this paper by pushing the power amplifier (PA) at the transmitter to operate in the nonlinear region, even near to the saturate point. Linearization reception technique is then adopted at the legal user's receiver to remove the distortion caused by the nonlinear PA, so that the distortion-free signal can be drawn, and correct demodulation and decoding could be achieved. While for the eavesdroppers, the information required to complete the nonlinear reception could hardly be obtained, since the critical training sequence is designed to be invisible to the eavesdropping users, so the security transmission between the legitimate users can be obtained. Then, the security capacity by nonlinear transmission is analyzed in the MIMO–OFDM systems, where the signal to distortion plus noise ratio is derived, and the upper approximation is also presented. Numerical simulations are carried out to verify the effectiveness of the proposed scheme with practical reception algorithm, and it is shown that obvious security capacity can be acquired with both memory and memoryless PAs. [ABSTRACT FROM AUTHOR]

The deployment of power line communication (PLC) has gained tremendous attention in recent times because of the dawn of the internet, the increasing need for fast connectivity, and it does not require any new wiring installations which significantly reduces the deployment costs. Power lines are originally designed to transmit power from the suppliers to the customers at low frequency (50 Hz or 60 Hz). They are used to improve communication infrastructure, therefore making them useful as a communication channel. This paper presents an investigation of the use of the existing power grid line as a medium for Broadband communication by using orthogonal frequency division multiplexing (OFDM) technology at the transceiver. The transmitter performs coding of data signals to keep it from fading and radiation. In order to repair signals attenuated and affected by noise during transmission over the power line, the decoupling and OFDM receiver performs filtering and decoding, respectively. In the OFDM transmitter, quadrature phase-shift keying (QPSK) modulation as well as the OFDM receiver QPSK demodulation are used to create a set of data symbols and to predict the probability of errors. An error of 0.036 dB was obtained, which is in the allowable range of signals with good quality to be transmitted to the customers. The Coupling circuit is used as the heart of the system design and is used to insert the modulated signals from the transmitter to the power line. It is also used to extract the signals from the receiver, and to protect the circuit from medium and low voltage and low-frequency signals (less than or equal to 32 kV and 50 Hz). [ABSTRACT FROM AUTHOR]

In this work, the performance of layered transmission with optimum decoding order and multiuser diversity is analyzed in a K-user downlink network. The transmitter is equipped with two antennas whereas every user has r ( r ≥ 2 ) antennas. In each training period, the transmitter opportunistically schedules a single user based on a set of scalar feedback (FB) values sent back from the users. Investigating on what should be fed back, three distinct FB strategies are studied and an exact joint distribution expression is derived in each case for the evaluation of the average outage probability. Analytical results are obtained without disregarding the impact of error propagation and broadly differ from the former approximated analyses. It is shown that one of the inspected strategies clearly outperforms the others and can achieve full multiuser diversity gain of K. We show that by just a scalar FB from the users to the transmitter, which can easily be quantized in accordance with the desired accuracy, a significant power gain can be accomplished at the transmitter as compared to a single-user scenario. For the mathematical analysis, we rely on the fact that all orderings are equiprobable under independent and identical fading. To that end, we obtain the joint distribution of the ordered gains from the joint distribution of the unordered gains. [ABSTRACT FROM AUTHOR]

The performance of CMOS transmitters and receivers operating at the submillimeter electromagnetic wave frequencies have sufficiently improved for use in active transmission and reflection-mode imaging applications that have the potential for broad deployment and utilization. Imaging integrated circuits have the potential to be large in area to support a high number of pixels along with digital backend processing circuits. For high volume imaging applications that may eventually be included in automobiles, smartphones, laptops, tablets, and others, a large manufacturing capacity to support the volume of large area ICs is necessary. For this, the use of CMOS technologies with a much larger manufacturing capacity is favored. It should be possible to improve the performance of CMOS circuits to increase the range, and operation margin and frequency. The electronically steerable submillimeter-wave reflector technology holds the promise for improving the performance and energy efficiency of submillimeter-wave imaging systems by multiple orders of magnitude, and it is a critical research area. Increasing the operating frequency from 430 to 850 GHz using CMOS integrated circuits to improve the angular resolution by 2X at a given form factor (∼0.15° for a reflector diameter of 15 cm) can make the submillimeter-wave imaging competitive to the LIDAR angular-resolution performance, while providing superior capabilities in visually impaired conditions and making the imaging devices more affordable. [ABSTRACT FROM AUTHOR]

This article introduces a uniform theory of diffraction–physical optics (UTD–PO) formulation for analyzing radiowave multiple diffraction emanating from trees and buildings in green urban areas, considering illumination from a low transmitter and assuming spherical-wave incidence. Based on Babinet's principle, this solution models buildings as rectangular sections and accounts for the influence of tree crowns (assuming these rise above the average rooftop height) by incorporating appropriate attenuation factors/phasors into the diffraction phenomena of buildings. The validation of the formulation is achieved through measurements made at the 39 GHz 6G mmWave frequency on a scale model of a green urban environment comprising bonsai trees and bricks. The main advantage of the proposed solution is that the calculations only include single diffractions due to recursion, circumventing the need to use higher-order diffraction terms in the diffraction coefficients, thus reducing the computation time and power. Our results may be beneficial for the design of mobile communication systems, including 6G networks, situated in green urban areas and with transmission source positioned lower than the surrounding infrastructure. [ABSTRACT FROM AUTHOR]

The object of this study is a wireless local Wi-Fi network for broadcasting biomedical signals, its structure, and principles of construction. The task of minimizing the power consumption of a Wi-Fi transmitter has been addressed, which provides the possibility of building a wireless system for long-term monitoring of biomedical signals. As a result, a functional diagram of a wireless Holter monitoring system based on an ESP32 microcontroller was constructed, which includes a subsystem for setting up and diagnosing system units using MATLAB software packages, an ECG signal generator, and a multifunctional PCIe board from National Instruments. Evaluation criteria and methods for minimizing power consumption by an autonomous Wi-Fi transmitter have been proposed. Methods for synchronizing the working cycles of the transmitter and receiver of the Holter monitoring system were determined. A procedure for determining the optimal biosignal measurement frequency is presented, at which the distortion of ECG signals would be minimal, which means that the signal could be transmitted without losses. The concept of constructing an algorithm for implementing a program for a Wi-Fi transmitter has been developed, ensuring parallel execution of ECG signal measurement operations and their transmission over a local network. The data from semi-naturalistic tests with an experimental Holter monitoring system with a pre-setup subsystem and using external measuring devices, a computer, and the MATLAB software environment are presented. A comparative analysis of the experimental data with primary ECG signals and ECG signals at the receiver output showed a fairly stable correspondence between the input and output ECG signals. The proposed algorithms make it possible to reduce the average current consumption of the ESP32 microcontroller to 50.5 mA. The results of the study demonstrate the possibility of constructing an energy-efficient wireless system for long-term monitoring of biomedical signals based on the Wi-Fi interface. [ABSTRACT FROM AUTHOR]

In this study, we use a time-varying parameter vector autoregression in conjunction with the extended joint connectedness approach (TVPVAR-EJC) to examine the interrelationships among five variables, namely digitalization measured by the number of individuals using the Internet (% of the population), mobile cellular subscriptions (per 100 people), human capital index, CO2 emissions, and GDP, from 1996 to 2019 in Vietnam. Net total directional connectedness of digitalization and other variables suggests that it consistently acts as a net shock transmitter, whereas human capital was found to be a net receiver of corresponding shocks from 1997 to 2019. The emission of CO2 was a net critical receiver in 1998 but remained as a net transmitter for the rest of the period. Pairwise connectedness reveals that digitalization appeared as a net shock transmitter in connection with the human capital index and GDP. In the relationship with human capital, digitalization's role was critical. [ABSTRACT FROM AUTHOR]

This manuscript presents the use of three novel technologies for the implementation of wireless green battery-less sensors that can be used in agriculture. The three technologies, namely, additive manufacturing, energy harvesting, and wireless power transfer from airborne transmitters carried from UAVs, are considered for smart agriculture applications, and their combined use is demonstrated in a case study experiment. Additive manufacturing is exploited for the implementation of both RFID-based sensors and passive sensors based on humidity-sensitive materials. A number of energy-harvesting systems at UHF and ISM frequencies are presented, which are in the position to power platforms of wireless sensors, including humidity and temperature IC sensors used as agriculture sensors. Finally, in order to provide wireless energy to the soil-based sensors with energy harvesting features, wireless power transfer (WPT) from UAV carried transmitters is utilized. The use of these technologies can facilitate the extensive use and exploitation of battery-less wireless sensors, which are environmentally friendly and, thus, "green". Additionally, it can potentially drive precision agriculture in the next era through the implementation of a vast network of wireless green sensors which can collect and communicate data to airborne readers so as to support, the Artificial Intelligence and Machine Learning-based decision-making with data. [ABSTRACT FROM AUTHOR]

To facilitate temperature detection in industrial production settings, an optical fiber temperature transmitter was developed utilizing fluorescence lifetime as its basis. Comprising an upper computer, fiber optic temperature transmitter, and optical fiber probe, the system incorporates a scalable fluorescence detection module. Real‐time temperature calculation is achieved through a microcontroller based on the fluorescence lifetime, with results transmitted to the upper computer, the optical fiber sensor exhibits a resolution of 0.01°C and an accuracy of ±0.3°C. [ABSTRACT FROM AUTHOR]