Multiple Interference Research Articles

The Impact of Mobility on Physical Layer Security of 5G IoT Networks

Internet of Things (IoT) is rapidly spreading and reaching a multitude of different domains, since the fifth generation (5G) wireless technologies are the key enablers of many IoT applications. It is hence apparent that the broadcast nature of IoT devices makes data security unprecedentedly critical. Compared with traditional cryptography algorithms, which cannot cater for the features of IoT devices characterized by the severe limits in terms of energy, computation and storage capabilities, physical layer security (PLS) has been regarded as a promising solution to facilitate secure communications by exploiting the intrinsic randomness of the wireless medium. However, most of previous works assumed that all devices are static, and the impact of mobility on PLS deserves further investigation. In this paper, applying two types of random mobile models, i.e., the models of Random WayPoint (RWP) and Random Direction (RD), we study the impact of mobility on PLS in a scenario with three types of wireless devices (i.e., a destination, multiple interferers and an eavesdropper). Specifically, we establish an analytical framework for secrecy transmission capacity (STC), a fundamental metric in the study of PLS, under RWP and RD models. To the best of our knowledge, this is the first paper to derive STC and present the condition to achieve a positive STC with the consideration of mobility. We conclude that the RWP mobile destination can achieve a higher STC than that achievable in RD mobile and static scenarios, while RWP mobile eavesdropper is a challenging scenario to obtain a positive STC. Therefore, we propose an effective secrecy improvement strategy for the latter. Simulation validates the theoretical analyses.

Efficient prestack time migration velocity analysis: A correlation‐based global optimization approach

AbstractAn accurate migration velocity model is vital to seismic imaging. Conventional time‐domain migration velocity analysis techniques commonly obtain the velocity model by iteratively picking the velocity spectra of common reflection point gathers or scanning selection, which is usually laborious and computationally expensive. To solve these issues, we propose a more effective migration velocity analysis method for prestack time migration. This method is based on cross‐correlation stacked time shift functions of local migrated gathers and uses the very fast simulated annealing algorithm to semi‐automatically invert the migration velocity parameters. This new correlation‐based objective function can catch subtle bending features of the reflector in the local migrated gather. The proposed approach applies an efficient global optimization algorithm that does not depend on the initial parameter value and is easy to extend to the multiparameter complex case. Moreover, the strategy of using local migrated gathers can incorporate prior information in the inversion to avoid the effects of misidentifying reflection events and the interference of multiples. Furthermore, applying a dynamic parameter constraint strategy for the very fast simulated annealing algorithm improves the convergence speed. Both synthetic and real data examples demonstrate that the proposed migration velocity analysis method can efficiently build an accurate time migration velocity model, which can also provide a good initial velocity model for depth migration.

BM3D denoising-based multi-target detection method for complex background radar images

Abstract For the complex background of traditional radar image target detection methods is affected by multiple interferers, which leads to a low recognition rate of multi-target classification and a high false alarm rate. In this paper, the current hot research BM3D denoising method is introduced into radar image target detection. Firstly, the detection process of the BM3D algorithm is constructed, and the image pixels are reasonably clustered by denoising so that the image blocks in homogeneous regions have a high matching degree and those in non-homogeneous regions have a low matching degree. Secondly, the clustering recognition feature is used to limit the search range of similar blocks to homogeneous regions, to improve the denoising efficiency of the algorithm. Finally, the simulation results of this paper show that compared with previous algorithms, the BM3D detection method has significantly improved in both the subjective visual effect map and objective numerical indexes. For example, the image denoising quality is improved by about 0.716dB on average and up to 1.031dB, the image denoising time is shortened by about 19.962s on average, and the algorithm runs 1.211 times faster than the original algorithm. It is proved that the algorithm can improve denoising efficiency and reduce computational complexity while enhancing detailed information.

Multi-Target CFAR Detection Method for HF Over-The-Horizon Radar Based on Target Sparse Constraint in Weibull Clutter Background

High frequency radar has a wide monitoring range and low range resolution. It may contain multiple targets or outlier interference phenomena in different clutter regions of the range–Doppler (RD) spectrum in detected background. The key to the performance of target detection in multi target backgrounds is the ability to determine the attributes of targets or outliers. Our previous research shows that the number of targets belongs to an absolute minority compared to the number of background units. In this paper, we propose a new method for multi-target detection building on the ordered statistics constant false alarm detector (OS-CFAR). The new method fully utilizes the sparse characteristics of the target and uses the idea of introducing regularization processing to eliminate interfering targets, and obtain an estimate of shape parameters for target detection. To further improve the performance of the algorithm, a correction method is proposed for the inaccurate selection of the k value. Upon estimating the distribution parameters, the detection threshold is calculated, and the target’s constant false alarm detection is completed. Simulation and measured data show that our algorithm can effectively counter the interference of multiple targets and maintain a constant false alarm characteristic under different conditions, providing a reliable target detection method.

Accurate dipole radiation model for waveguide grating couplers

An analytical theoretical model for the waveguide grating coupler is developed and applicable to practical deep gratings. The grating-assisted input coupling efficiency is calculated by considering the reciprocal out-coupling problem. The deep grating structure is modelled as an optical layer filled with polarization dipole sources, and the scattered fields are then calculated using the associated Green’s functions and taking into account the multiple reflections and interference from the adjacent layers. The joint loss between the grating region and the waveguide is also considered. Comparison with numerical simulations shows very good agreement and validates the accuracy of the analytical model. The model explicitly describes the importance of multilayer interference of the scattered fields and guided-mode joint loss on the total grating-assisted coupling efficiency and can be used for practical waveguide grating coupler design with negligible computation workload.

Ultrasonic Wave Mode-Based Application for Contactless Density Measurement of Highly Aerated Batters.

An ultrasonic wave mode-based method for density measurement in highly foamed batters was developed. Therefore, a non-contact ultrasonic sensor system was designed to generate signals for batch-wise processes. An ultrasonic sensor, containing a piezoelectric ceramic at the fundamental longitudinal frequency of 2 MHz, was used to take impedance measurements in pulse-echo mode. The ultrasonic signals were processed and analysed wave-mode wise, using a feature-driven approach. The measurements were carried out for different mixing times within a container, with the attached ultrasonic sensor. Within the biscuit batter, the change to the ultrasonic signals caused by density changes during the batter-mixing process was monitored (R2 = 0.96). The density range detected by the sensor ranges between 500 g/L and 1000 g/L. The ultrasonic sensor system developed also shows a reasonable level of accuracy for the measurements of biscuit batter variations (R2 > 0.94). The main benefit of this novel technique, which comprises multiple wave modes for signal features and combines these features with the relevant process parameters, leads to a more robust system as regards to multiple interference factors.

Dual-mode bidirectional multifunctional chiral metamaterial based on self-complementary resonators

In this paper, we propose an intrinsic chiral metamaterial (ICM) consisting of two metal self-complementary resonators, dielectric layer, and an embedded continuous vanadium dioxide (VO2) layer, which can operate in reflection and transmission modes and tailor different polarization manipulations for circular and linear polarized waves in opposite incident directions. When VO2 is in metallic state, the ICM can achieve broadband and narrowband circular polarization conversions at 1.52–2.50 THz and 2.93 THz for opposite propagating directions, respectively; when VO2 is in an insulating state, it shows a strong asymmetric transmission (AT) effect at 2.43 and 3.19 THz for forward and backward linear polarized waves. In addition, the physical mechanisms of different polarization operations are explained by analyzing the surface current and electric field distributions, multiple interference model, and near-field distributions in detail, and the circuit models are introduced to verify the simulated results. Furthermore, we investigate the influence of structural parameters on performance. The proposed ICM has important implications for the development of polarization detectors, frequency selectors, etc.

A Primer on Rate-Splitting Multiple Access: Tutorial, Myths, and Frequently Asked Questions

Rate-Splitting Multiple Access (RSMA) has emerged as a powerful multiple access, interference management, and multi-user strategy for next generation communication systems. In this tutorial, we depart from the orthogonal multiple access (OMA) versus non-orthogonal multiple access (NOMA) discussion held in 5G, and the conventional multi-user linear precoding approach used in space-division multiple access (SDMA), multi-user and massive MIMO in 4G and 5G, and show how multi-user communications and multiple access design for 6G and beyond should be intimately related to the fundamental problem of interference management. We start from foundational principles of interference management and rate-splitting, and progressively delineate RSMA frameworks for downlink, uplink, and multi-cell networks. We show that, in contrast to past generations of multiple access techniques (OMA, NOMA, SDMA), RSMA offers numerous benefits: 1) enhanced spectral, energy and computation <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">efficiency</i> ; 2) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">universality</i> by unifying and generalizing OMA, SDMA, NOMA, physical-layer multicasting, multi-user MIMO under a single framework that holds for any number of antennas at each node (SISO, SIMO, MISO, and MIMO settings); 3) flexibility by coping with any interference levels (from very weak to very strong), network loads (underloaded, overloaded), services (unicast, multicast), traffic, user deployments (channel directions and strengths); 4) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">robustness</i> to inaccurate channel state information (CSI) and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">resilience</i> to mixed-critical quality of service; 5) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">reliability</i> under short channel codes and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">low latency</i> . We then discuss how those benefits translate into numerous opportunities for RSMA in over forty different applications and scenarios of 6G, e.g., multi-user MIMO with statistical/quantized CSI, FDD/TDD/cell-free massive MIMO, millimeter wave and terahertz, cooperative relaying, physical layer security, reconfigurable intelligent surfaces, cloud-radio access network, internet-of-things, massive access, joint communication and jamming, non-orthogonal unicast and multicast, multigroup multicast, multibeam satellite, space-air-ground integrated networks, unmanned aerial vehicles, integrated sensing and communications, grant-free access, network slicing, cognitive radio, optical/visible light communications, mobile edge computing, machine/federated learning, etc. We finally address common myths and answer frequently asked questions, opening the discussions to interesting future research avenues. Supported by the numerous benefits and applications, the tutorial concludes on the underpinning role played by RSMA in next generation networks, which should inspire future research, development, and standardization of RSMA-aided communication for 6G.

The phase spiral in Gaia DR3

Aims. We aim to study the phase spiral in the Milky Way (MW) disc with data from the third data release of Gaia (DR3) and use it as an inference tool to decipher the late-time evolution of the Galaxy. Methods. We used an edge-detection algorithm to find the border of the phase spiral, allowing us to robustly quantify its shape at different positions and for different selections. We calculated the time of onset of the phase-mixing by determining the different turns of the phase spiral and using the vertical frequencies from commonly used models of the gravitational potential of the MW. Results. We find that the phase spiral extends down to −1.2 kpc in height below the plane (about 3–5 scale heights of the thin disc) and beyond ±50 km s−1 in VZ. We see a secondary branch mostly at positive vertical velocities when coloured by azimuthal velocity and in the counts projection. We also find complex variations of the phase spirals with angular momentum and azimuth. All these findings are possible evidence of multiple perturbations (from different times or from different perturbers) and/or of the complexity of the phase-mixing process. We detect the phase spiral from 6 to 11 kpc from the Galactic centre and find signatures of vertical asymmetries 1–2 kpc beyond this range. We measure small but clear variations with azimuth. When we determine the phase mixing times from the phase spiral at different angular momenta and using the different spiral turns (at different Z), we obtain inconsistent times with systematic differences (times increasing with |LZ| and with |Z|). Our determinations are mostly in the range of [0.3–0.9] Gyr, with an average of 0.5 Gyr. The inconsistencies do not change when using different commonly used potential models for the MW, different stellar distances, or frequencies for different kinetic temperatures; they could stem from the inconsistency of the assumed gravitational potentials with the true MW, and from oversimplification of the modelling, in particular where self-gravity is neglected or where multiple perturbations and/or interference with other processes are not considered. Conclusions. The wealth of information provided by the new Gaia DR3 data should encourage us to make progress in crucial modelling aspects of the disc dynamics, such as non-equilibrium, self-gravity, propagation of different types of bending waves, and interactions between different mechanisms. Such advancements could finally enable us to establish the origin of the phase spiral and its relation to the Sagittarius dwarf galaxy.

Multistage FPGA Least Mean Squares Filters Suppressing Multiple Narrowband Radio-Frequency Interferences in the Radio Detection of Cosmic Rays

The article presents the FPGA implementation of 256- and 768-stage Least Mean Squares filters with rectangular, Hamming and Kaiser windows to suppress at least 10 narrow-bands RFIs. The analysis shows extremely high efficiency Radio Frequency Interference (RFI) elimination. 9-bit real cosmic ray data from the Auger Engineering Radio Array (AERA) was used as patterns and mixed with 14-bit multiple narrow-band RFIs. They were hidden deep within RFI’s background. After the cleaning process, the patterns were brought out and are practically without contamination.

Guest Editorial Rate Splitting for Future Wireless Networks

Rate splitting (RS) and rate splitting multiple access (RSMA) have emerged as a promising and powerful multiple access, interference management, and multi-user strategy for next-generation wireless systems and networks. This Special Issue is entirely dedicated to the theory, design, optimization, and applications of RS and RSMA in various network configurations. It starts with a guest editor-authored tutorial paper [A1] that delineates the basic principles and applications of RS and RSMA. The tutorial paper is then followed by 17 technical papers.

Bifunctional Terahertz Metasurface for Transmissive Broadband Linear-to-Circular and Linear Polarization Conversion

In this work, we experimentally demonstrate a bifunctional terahertz (THz) metasurface that can achieve broadband linear-to-circular polarization conversion (LCPC) and linear polarization conversion (LPC) in two different bands, respectively. The measured 3-dB axial ratio relative bandwidth is 34.2% for the LCPC in the lower band from 0.34 THz to 0.48 THz, and the measured polarization conversion ratio is over 80% for the LPC in the higher band from 0.53 THz to 0.85 THz. The physical mechanism of the LCPC and LPC is explained by the surface current distribution and is further discussed by employing the multiple interference model. This bifunctional THz metasurface polarization converter has promising applications in THz systems, communications, spectroscopy, etc., and the design strategy can also be extended to microwave and millimeter bands.

Exact analysis of maximal ratio transmission‐based decode‐and‐forward relaying with arbitrary number of co‐channel interferers

SummaryThis paper analyzes the performance of maximal ratio transmission (MRT)‐based cooperative communication system over Nakagami‐ fading channels in the existence of co‐channel interference which is becoming a critical factor since the limited spectrum bands are shared by growing number of devices. In particular, a dual‐hop decode‐and‐forward relaying is investigated when multiple interferers affect the relay and the destination nodes. Firstly, the cumulative distribution function (CDF) and the probability density function (PDF) of the signal‐to‐interference‐plus‐noise ratio (SINR) are derived. Then, the exact expressions for the outage probability (OP), average bit error probability (ABEP), and ergodic capacity are obtained. Furthermore, asymptotic expressions for OP and ABEP are provided to find the diversity and coding gains. Finally, simulation results are presented to validate our theoretical findings.

Addressing Multi-User Interference in Vehicular Visible Light Communications: A Brief Survey and an Evaluation of Optical CDMA MAC Utilization in a Multi-Lane Scenario.

Visible Light Communications (VLC) are developing as an omnipresent solution for inter-vehicle communications. Based on intensive research efforts, the performance of vehicular VLC systems has significantly improved in terms of noise resilience, communication range, and latencies. Nevertheless, in order to be ready for deployment in real applications, solutions for Medium Access Control (MAC) are also required. In this context, this article provides an intensive evaluation of several optical CDMA MAC solutions and of their efficiency in mitigating the effect of Multiple User Interference (MUI). Intensive simulation results showed that an adequately designed MAC layer can significantly reduce the effects of MUI, ensuring an adequate Packet Delivery Ratio (PDR). The simulation results showed that based on the use of optical CDMA codes, the PDR can be improved from values as low as 20% up to values between 93.2% and 100%. Consequently, the results provided in this article show the high potential of optical CDMA MAC solutions in vehicular VLC applications, reconfirm the high potential of the VLC technology in inter-vehicle communications, and emphasize the need to further develop MAC solutions designed for such applications.

Full-domain collaborative deployment method of multiple interference sources and evaluation of its deployment effect

This paper realizes the full-domain collaborative deployment of multiple interference sources of the global satellite navigation system (GNSS) and evaluates the deployment effect to enhance the ability to disturb the attacker and the capability to defend the GNSS during navigation countermeasures. Key evaluation indicators for the jamming effect of GNSS suppressive and deceptive jamming sources are first created, their evaluation models are built, and their detection procedures are sorted out, as the basis for determining the deployment principles. The principles for collaboratively deploying multi-jamming sources are developed to obtain the deployment structures (including the required number, structures in demand, and corresponding positions) of three single interference sources required by collaboratively deploying. Accordingly, simulation and hardware-in-loop testing results are presented to determine a rational configuration of the collaborative deployment of multi-jamming sources in the set situation and further realize the full-domain deployment of an interference network from ground, air to space. Varied evaluation indices for the deployment effect are finally developed to evaluate the deployment effect of the proposed configuration and further verify its reliability and rationality.

Фильтрация сигналов при скачкообразных мультипликативных помехах

The problem of constructing the approximately optimal Bayesian algorithm of filtering the output signal for a linear stochastic dynamical system is solved. Non-linear mixture of the output signal and of the multiplicative interference was measured. This interference is a continuous-valued random process with the unknown distribution law within the given limits of [c(1), c(2)], c(1) &gt; 0, c(2) &gt; 0, and in the frequency range of [0, ∆ω]. The filtering algorithm is synthesized by the approximately optimal signal estimation method based on the theory of systems with random jump structure and the method of two-time parametric approximation of the phase coordinates probability distribution. The method consists in approximate replacement of the unknown probability densities of phase coordinates by the known distribution laws with the unknown mathematical expectations and covariances determined as a result of solving the problem. The proposed approximate-optimal filtering algorithm is based on replacement of the continuous-valued multiplicative interference by a random jump process, i.e., Markov chain with two states c(1), c(2) and equal intensities of transitions from one state to another q′ = 2∆ω. Conditional probability densities of the output signal for fixed states of the Markov chain c(1), c(2) are approximated by gamma distributions that depend on mathematical expectations and variances of the x(t) signal at the fixed c(1), c(2) and measurements x(t) in a mixture with the Markov jump interference. An example of constructing an algorithm for evaluating the distance from an aircraft to the object based on object irradiance measurement by the infrared direction finder was considered. Irradiance was equal to the radiation strength ratio to the square of the distance. Radiation strength, i.e., multiplicative interference, was the random process with unknown continuous distribution in a limited range. The approximate-optimal filter was constructed for distance evaluation by replacing this process with a two-state Markov chain and approximating the distance probability density by the Rayleigh distribution

Wearable electrochemical gas sensor for methanol leakage detection

To ensure worker and environmental safety in daily work, it is an urgent need in industrial safety field to construct wearable sensing devices for volatile organic compounds (VOCs) leakage detection in chemical production. In this work, methanol gas was selected as the research object, and the wearable gas sensor has been constructed on a flexible substrate for systematically investigating the sensing process and performance, as well as practicality of leak detection. Electrochemical measurements demonstrated the constructed sensor possessed obvious electrocatalytic capability at 0.6 V, good linearity in the detection range of 20–100 ppm, 200–3000 ppm and 4000–30,000 ppm, and low limit of detection (3.3 ppm). This methanol gas sensor also exhibited high reproducibility, lifetime, and stable sensitivity according to the continuous repeated and long-time stability measurement results. High gas-sensitive selectivity to methanol under multiple interference gases, such as acetone, toluene, xylene, methylene chloride, acetonitrile had been demonstrated, and the response change under selectivity test was less than 16%. Significantly, it also displayed detectability in actual methanol gasoline sample, and the response time was less than 16 s. Moreover, experimental results also have proved higher content of platinum (20%) with better theoretical CO-tolerance capacity and sensing sensitivity. When maintaining a platinum content of 20%, the introduction of support materials with high specific surface area and conductivity in place of activated carbon will ensure that all sites are catalytically active, further improve the sensing sensitivity and be extended to the design of other VOCs sensors.

Mathematical model of spatial and temporal processing of broadband signals in satellite radio systems of broadband access and radio navigation

To effectively receive a useful broadband signal, it is necessary to compensate for distortions caused by the complex frequency-dependent coefficient of the receiving and transmitting antenna, multiplicative interference and noise from the heterogeneity of the propagation medium, additive interference and noise. Using only correlation processing under certain conditions will not allow receiving a useful broadband signal with the required quality. The article develops a mathematical model of spatio-temporal processing of broadband signals in satellite broadband access systems, showing that spatio-temporal processing should be carried out in two stages. At the first stage, space-time processing is carried out in the channel adaptively to the antenna array based on the formation of a complex frequency-dependent vector of weighting coefficients, which should change with a change in the signal-interference situation in real time, taking into account the change in the direction of radiation sources. At the second stage, correlation processing of the broadband signal is performed based on the use of long-length code sequences. This model is the basis for the development of methods for the formation and correlation (temporal) processing of broadband signals and methods of spatio-temporal processing of broadband signals under conditions of intentional and unintentional exposure. Based on the presented mathematical model of spatio-temporal processing of broadband signals, the main directions of increasing the noise immunity of radio-electronic systems are determined.

Ultra‐Broadband, Tunable, and Transparent Microwave Meta‐Absorber Using ITO and Water Substrate

AbstractIntegrating broadband absorption, dynamic tunability, and high optical transparency into a single microwave absorber remains a crucial challenge. Here, an ultra‐broadband, tunable, and transparent microwave meta‐absorber comprising double‐layer indium tin oxide resonant patterns and a water‐based substrate is theoretically presented and experimentally demonstrated. Experimental measurements indicate that the designed meta‐absorber can achieve over 90% absorption in an ultra‐broadband frequency range of 12.49–98.21 GHz with a relative bandwidth of 154.9%, while the average optical transmittance is 60.49%. In addition, a multiple reflections interference model is employed to elucidate the physical mechanisms of the ultra‐broadband absorber. Furthermore, its absorption performance can be reversibly switched between ultra‐broadband and dual‐broadband by altering the water substrate thickness. These peculiar properties make the proposed meta‐absorber more favorable for practical applications in modern stealth materials and optical windows.

Fast three-dimensional DNA walker based on space double-confinement catalytic hairpin assembly for ultrasensitive homogeneous electrochemiluminescence detection of sonic hedgehog

DNA walkers have been widely used to build biosensing systems. However, their moving efficiency was limited, which has hindered practical applications. Here, we for the first time integrated localized CHA with nanoscale AuNPs scaffolds to achieve space double-confined catalytic hairpin assembly (SDCHA) for developing a fast three-dimensional DNA walker. Driven by spatially proximal displacement, the walker possessed a high walking speed, which was about 8 times, 9 times and 23 times faster than LCHA, CHA-AuNPs and conventional CHA, respectively. Moreover, the walking time was about 1.4–8.3 times shorter than most recently reported DNA walkers and space-confined strand displacement reactions. By further integrating it with magnetic probes and g-C3N4 nanosheets, an ultrasensitive and enzyme-free homogeneous electrochemiluminescence (Ho-ECL) aptasensor was firstly constructed for sonic hedgehog (SHh) detection. Profiting from this tailored integration, the Ho-ECL aptasensor avoided multiple interferences from complex milieu as well as tedious procedures of electrode modifying and washing, showing good signal stability, repeatability and reliability. It was also proved to achieve ultrasensitive SHh detection with the detection limit as low as 13.5 fM, superior to previous research on SHh detection. This work might broaden ideas for the construction of fast DNA walkers and facile Ho-ECL bioanalytical methods for clinical diagnosis.