Signal Propagation Characteristics Research Articles

ASGR: An Artificial Spider-Web-Based Geographic Routing in Heterogeneous Vehicular Networks

Recently, vehicular ad hoc networks (VANETs) have been attracting significant attention for their potential for guaranteeing road safety and improving traffic comfort. Due to high mobility and frequent link disconnections, it becomes quite challenging to establish a reliable route for delivering packets in VANETs. To deal with these challenges, an artificial spider geographic routing in urban VAENTs (ASGR) is proposed in this paper. First, from the point of bionic view, we construct the spider web based on the network topology to initially select the feasible paths to the destination using artificial spiders. Next, the connection-quality model and transmission-latency model are established to generate the routing selection metric to choose the best route from all the feasible paths. At last, a selective forwarding scheme is presented to effectively forward the packets in the selected route, by taking into account the nodal movement and signal propagation characteristics. Finally, we implement our protocol on NS2 with different complexity maps and simulation parameters. Numerical results demonstrate that, compared with the existing schemes, when the packets generate speed, the number of vehicles and number of connections are varying, our proposed ASGR still performs best in terms of packet delivery ratio and average transmission delay with an up to 15% and 94% improvement, respectively.

Mathematical analysis of the signal propagation characteristics of neuronal networks

AbstractIt is important to understand the relationship between spatiotemporal patterns of neuronal populations and information processing of the brain for medical and engineering purposes. Although, there are some methods to record neuronal population, basically only the information about firing rate can be obtained from those methods. Therefore, some methods are suggested to estimate the internal state of the neuronal population from the information about firing. In this research, we investigated the relationship between firing rates and responses to external electrical stimuli by using neuronal population models. We developed a method to manipulate neuronal parameters to make neuronal populations exhibit different dynamical properties while keeping firing rates intact. As a result, we found that there are some cases where the internal states are different even though they share the same firing rate. This result suggests that there is some information that cannot be obtained by using only the information about firing rates.

Artifact-free imaging through a bone-like layer by using an ultrasonic-guided photoacoustic microscopy.

Reflection artifacts caused by a bone-like layer badly degrade the quality of photoacoustic images in many biomedical applications, e.g.,in vivo brain imaging through the skull. We proposed an ultrasonic-guided photoacoustic microscopy (PAM) to remove the reflection artifacts. This system is developed from dual-mode microscopy, integrating a scanning acoustic microscopy with a conventional PAM. Based on similar propagation characteristics of a photoacoustic signal and ultrasonic echo in a bone-like layer, we employ the ultrasonic echo as a filter to remove the multiple reflected artifacts in photoacoustic signals and obtain artifact-free images. An experiment of imaging a phantom below a bone-like film is used to demonstrate the performance of this method. The results suggest that this method can achieve an artifact-free image of the phantom under the film successfully, whereas the conventional PAM fails to achieve clean images of the vessel-like absorbers. This study might improve the imaging quality of PAM in many biomedical applications.

A computationally efficient model for determining sound speed in shallow tropical freshwater systems, with field validation

AbstractThe optimum performance of any underwater system depends on the propagation characteristics of the acoustic signals in the local water medium. Shallow tropical freshwater systems suffer from sub‐optimal performance of sonar systems deployed for any acoustic sensing because of random fluctuations of the water medium. The propagation characteristics depend largely on the sound speed variations defined by the site‐specific physical parameters such as water temperature, salinity and depth. The present study focuses on analysing the sound speed profile of a typical shallow freshwater system (Khadakwasla Lake; 18.43°N, 73.76°E), using regression models with the goal of deriving a computationally efficient model. To this end, a linear and polynomial regression model was developed, and their performance compared with the results of the model of Chen and Millero (), based on root mean square error (RMSE). In situ measurements of electrical conductivity, temperature and density (CTD) were carried out using a Valeport 602 CTD meter. Approximately 125 CTD samples were obtained during a 2‐day experimental study conducted at Khadakwasla Lake from 11 October 2017 to 12 October 2017. The data collection was undertaken throughout the day at multiple locations in the lake over a spatial distance of ~16 km. The Valeport 602 CTD meter uses the Chen and Millero () formula, considered the most conventional sound speed equation. The computational complexity of the proposed models was measured in terms of the number of addition and multiplication operations required. The validation of both models was carried out by varying the model input parameters within defined limits. The model inputs have been derived from an in situ experimental data collection process in a typical shallow tropical freshwater system. The linear regression model exhibited an RMSE of 4.15 m/s, while the polynomial regression model exhibited a good agreement with an RMSE of 0.5 m/s.

MineSense: sensing the radio signal behavior in metal and non-metal underground mines

The requirement for consistent well-being upgrades of mine personnel and improved mine productivity is encouraging the underground mining industry through a move from manual to automated mine operations. From a communication point of view, this move introduces a new set of challenges and design goals of business driven and emergency response applications that need to be addressed by wireless technology. Solution based on wireless technology has a wide scope of deployment in underground mines supporting applications such as environmental monitoring, ventilation on demand, tracking of miners and remote asset monitoring, etc. However, the reliable operation of such networks is restricted in real time due to the unique characteristics of underground mines such as gallery dimension, humidity, curves and bends, support systems, noise etc. In addition, the lack of experimental understandings of electromagnetic wave propagation in such high stress environment affect the features offered by these technologies. In this work, we have focused on empirical understandings of radio signal behavior in different underground mines. The contribution of this work is three fold. First, it outlines the impact of depth on the signal propagation characteristics and then identifies the major propagation factor contributing to significant losses at the receiver in the mine tunnel space. Second, based on the propagation data collected at different metal and non-metal mines, discusses the role of mining methods on radio signal behavior. Third, it critically presents the need for modifications in formulations of the theoretical channel model which have been characterized by extensive data measurements in operational underground mines. The observations reported in this work may significantly help the wireless design community to achieve reliable and optimized performance of communication devices to be deployed in such high stress work environments.

Research on Calibration Method of Underwater Shock Wave Pressure Measurement Sensor Systemt

Underwater explosions are distinguished from explosions in the air, and their environment is complex, making sensor systems more difficult to calibrate. In this paper, the calibration method of underwater shock wave pressure sensor system is studied. The dynamic pressure calibration method based on water shock tube is proposed to calibrate the system. The propagation characteristics of the pulse pressure signal in the water shock tube are studied. The water shock tube device suitable for the calibration of the underwater shock wave pressure sensor system is designed. In the end, the advantages of the water shock tube in measuring the underwater shock wave pressure are summarized.

Mathematical Analysis about Signal Propagation Characteristics of Neuronal Networks

Mathematical Analysis about Signal Propagation Characteristics of Neuronal Networks

Researches on very low frequency acoustic signal propagation characteristics in different shallow elastic wedge bottoms

Targeted at the issue of extremely low-frequency (<100Hz) acoustic propagation in complex shallow elastic bottom environments. The influence law of different complex elastic bottoms on the acoustic signal propagation at very low frequency by acoustic energy flux has been analyzed with the simulation, which is based on the finite element method. The elastic bottoms which have been studied are the shallow horizontal elastic bottom, and the up-sloping and the down-sloping elastic bottom. The results show that the acoustic signal propagating in the up-sloping and down-sloping elastic bottom environments is more complex than that propagating in the horizontal elastic bottom, and the acoustic energy leaking into those elastic bottoms has very different influence on the acoustic signal propagation, especially in the up-sloping bottom.

Channel Characterization and Path Loss Modeling in Indoor Environment at 4.5, 28, and 38 GHz for 5G Cellular Networks

The current propagation models used for frequency bands less than 6 GHz are not appropriate and cannot be applied for path loss modeling and channel characteristics for frequency bands above 6 GHz millimeter wave (mmWave) bands, due to the difference of signal propagation characteristics between existing frequency bands and mmWave frequency bands. Thus, extensive studies on channel characterization and path loss modeling are required to develop a general and appropriate channel model that can be suitable for a wide range of mmWave frequency bands in its modeling parameter. This paper presents a study of well-known channel models for an indoor environment on the 4.5, 28, and 38 GHz frequency bands. A new path loss model is proposed for the 28 GHz and 38 GHz frequency bands. Measurements for the indoor line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios were taken every meter over a separation distance of 23 m between the TX and RX antenna locations to compare the well-known and the new large-scale generic path loss models. This measurement was conducted in a new wireless communication center WCC block P15a at Universiti Teknologi Malaysia UTM Johor, Malaysia, and the results were analyzed based on the well-known and proposed path loss models for single-frequency and multifrequency models and for directional and omnidirectional path loss models. Results show that the large-scale path loss over distance could be modeled better with good accuracy by using the simple proposed model with one parameter path loss exponent PLE (n) that is physically based to the transmitter power, rather than using the well-known models that have no physical base to the transmitted power, more complications (require more parameters), and lack of anticipation when explaining model parameters. The PLE values for the LOS scenario were 0.92, 0.90, and 1.07 for the V-V, V-H, and V-Omni antenna polarizations, respectively, at the 28 GHz frequency and were 2.30, 2.24, and 2.40 for the V-V, V-H, and V-Omni antenna polarizations, respectively, at the 38 GHz frequency.

Influence of insulators on the propagation characteristics of UHF signals

The partial discharge (PD) in gas‐insulated switchgear (GIS) will stimulate the ultra‐high frequency (UHF) electromagnetic (EM) wave signal of 300 MHz to ∼3 GHz. The PD signal will appear in the resonance, distortion, and attenuation during propagating in GIS due to the complexity of the internal structure of GIS. Thus, it increases the intricacy of detection and evaluation. The Finite difference time domain (FDTD) algorithm has been used in this paper to investigate the influence of the insulator structure parameters on the propagation characteristics of the UHF signal. The results show that the dielectric loss of insulator causes the attenuation of the UHF signal inside and outside GIS, with an increase in the thickness and dielectric constant of the insulator. The shape of the insulator has little influence on the propagation characteristics of the UHF signal within GIS. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Effect of disconnector and high‐voltage conductor on propagation characteristics of PD‐induced UHF signals

UHF (ultra high frequency) method has been widely used in PD (partial discharge) detection for its high sensitivity. The resonance, distortion, and attenuation appearing in the propagation process of UHF signals in GIS (gas insulated switchgear) will influence the real situation of PD detection. Therefore, it is necessary to investigate the effect of GIS components such as disconnectors or high voltage conductors on the propagation characteristics of PD-induced UHF signals in various voltage classes GIS. The factors of PD signals propagation characteristics in axial and radial directions are both analysed to avoid the effect caused by placement of sensor in this paper. First, the simulation models of GIS are built based on FDTD (finite difference time domain) method. Then the propagation characteristics of PD-induced UHF signals are studied in the GIS with different disconnector gap lengths and different high voltage conductor radii. Finally, the reliability of the simulation results is verified by compared with laboratory tests. The disconnector gap and the change of conductor radii can both result in the signals attenuation which rises highest in the direction of 180°. The lower the GIS class voltage is, the larger the attenuation of signals after passing through disconnector gap is.

Characteristics of signal propagation in multiferroic majority logic gates subjected to thermal noise

The error rates of multiferroic majority logic gate (MLG) in the presence of thermal noise fluctuation are evaluated via solving the Landau–Lifshitz–Gilbert equations. It is found that in the pre-stress condition, magnetisation orientations of nanomagnets in the MLG denote an initial 4°–10° departure from the easy axis direction due to random thermal noise field. This phenomenon may be the main origin of switching errors of multiferroic logic gates at high temperature. Specifically, in the post-stress condition, it has been seen that larger spacing between nanomagnets leads to a high error rate, up to 50%, which arises from weak dipolar coupling interactions and strong thermal fluctuations. However, opposed to their expected, small spacing between nanomagnets leads to a higher error rate, up to 90%, which mainly arises from spontaneous magnetisation reversal induced by weak stress anisotropy energy. Therefore, moderate spacing is very important to MLG switching at room temperature, for example the optimal spacing is 250–310 nm for MLG constructed with nanomagnets having shape anisotropy energy of 623 kT. These findings can provide guides on multiferroic logic circuit design.

Quantitative study on the propagation characteristics of MMM signal for stress internal detection of long distance oil and gas pipeline

The metal magnetic memory (MMM) detection technology has great application potential in the field of stress internal detection of long distance oil and gas pipeline due to the non-contact online detection to stress damage; however, the scientific significance of the pipeline stress internal detection results is questioned because the detection signal is affected by the medium during propagation. To study the propagation characteristics of MMM signal, a three-dimensional magnetic balanced magneto-mechanical model is set up based on magnetic charge theory. In this paper, the distribution characteristics of the scattered magnetic field in the stress concentration region are exposed and the propagation characteristics of different components of MMM signal are quantitatively analyzed. Further, the influence of different media on MMM signal propagation is compared, and a systematic experimental study is conducted. The results indicate that MMM signal shows a first-order exponential decay with increasing propagation distance. During the propagation, the tangential signal decays rapidly, and the normal signal is stable and suitable for locating the stress concentration regions. MMM signal decays faster in ferromagnetic medium than in non-ferromagnetic medium.

Simulation analysis on the propagation of the optical partial discharge signal in I-shaped and L-shaped GILs

When partial discharge (PD) occurs in the gas-insulated transmission line (GIL), accompanied by the occurrence of sound, light, electricity and thermal phenomena, the propagation characteristics of the optical PD signal are the basis for the arrangement of the optical sensors and PD source location. To study the propagation characteristics, simulation models of GIL are established. The total irradiance map (TIM) and the average value of the relative irradiance (AVRI) for the optical PD signal on each detection plane are observed under different PD source positions, detection distances and L-shaped angles. The simulation results indicate that 1) when the PD occurs near the inner conductor or the tank inner surface, it is more difficult to detect than other places. Taking the distance between the detection plane and the PD source (DDP), which is 60 cm, as an example, when the position of the PD source (PPS) is Up-50 mm, the AVRI is 79.56% of that when the PPS is Up-140 mm. 2) In the process of the L-shaped angles increasing, the value of relative irradiance has a certain increase. Taking the PPS below-95 mm as an example, when the L-shaped angle is 165°, the relative irradiance is 29.92% larger than that when the L-shaped angle is 90°. These findings can provide some reference for the optical PD detection in GIL.

Observed Propagation Route of VLF Transmitter Signals in the Magnetosphere

AbstractSignals of powerful ground transmitters at various places have been detected by satellites in near‐Earth space. The study on propagation mode, ducted or nonducted, has attracted much attentions for several decades. Based on the statistical results from Van Allen Probes (data from October 2012 to March 2017) and DEMETER satellite (from January 2006 to December 2007), we present the ground transmitter signals distributed clearly in ionosphere and magnetosphere. The observed propagation route in the meridian plane in the magnetosphere for each of various transmitters from the combination of DEMETER and Van Allen Probes data in nighttime is revealed for the first time. We use realistic ray tracing simulation and compare simulation results against Van Allen Probes and DEMETER observation. By comparison we demonstrate that the observed propagation route, with partial deviation from the field lines corresponding to ground stations, provides direct and clear statistical evidence that the nonducted propagation mode plays a main role, although with partial contribution from ducted propagation. The propagation characteristics of VLF transmitter signals in the magnetosphere are critical for quantitatively assessing their contribution to energetic electron loss in radiation belts.

Study on the Propagation Characteristics of Partial Discharge in Switchgear Based on Near-Field to Far-Field Transformation

Ultra-high frequency (UHF) electromagnetic (EM) signals generated by the partial discharge (PD) process of high-voltage equipment are now widely used in PD detection. The computation of EM propagation generated by a local discharge source using a uniformly hardwiring source can hardly reveal the discharge characteristics. In this paper, a method of near-field to far-field transformation is proposed to realize the study of the propagation characteristics of the PD signal. A short gap discharge model is established to get the near-field electromagnetics and the proposed method is validated by comparing the directly calculated results with the results of the near-field source. In the end, a model of switchgear is employed to study the propagation characteristics of the EM signal based on the proposed method. Via numerical calculation, the influence of the equipment in the switchgear on the propagation of the discharge EM is studied. It is found that the direction of the discharge source has a significant effect on the distribution of the electric field, which indicates that the discharge source cannot be simplified to a uniformly hardwiring source. In addition, it is also obtained that the amplitude of the electric field shows the same trend with the growth of the discharge channel, which gives a method for evaluating the development of the PD. Particularly, the near-field to far-field transformation can provide an effective method for studying the propagation of discharge EM waves in large-scale equipment.

Vortex channel modelling for the radio vortex system

In this paper, a free-space vortex channel model of the radio vortex system is proposed to describe the propagation characteristics of vortex signals over the vortex channel. The key idea is to combine the Laguerre-Gaussian (LG) modes in the optical field with the free-space propagation model in the radio field. The proposed free-space vortex channel model is derived from the electric field expression of the LG modes and the freespace channel transfer function of the freespace propagation model theoretically. Simulation results verify that the proposed model could reflect the vortex channel characteristics better than the currently used free-space propagation model.

Construction and analysis of multi-path propagation model for indoor short range Ultra-wideband signal based on time domain ray tracing method

The realization of the Internet of Things can not be separated from the wireless sensor network which was the extension of communication and perception. The shortage of spectrum resources will become one of the bottlenecks that hinder the rapid development of Internet of Things. A large number of sensor communication makes the interference problem of wireless channel more and more serious. Therefore, the research of wireless channel characteristics and model was important for development of Internet of Things. In this paper, the time domain multipath propagation characteristics of direct, reflection, diffraction and transmission were introduced, which provided a more accurate basis for the design of indoor short distance Ultra-wideband (UWB) communication model. Considering the practicability of simulation, the multipath propagation characteristics of UWB signals under indoor short distance environment with wooden furniture were studied. Moreover, Aluminium door partitions, glass partitions, and plastic furnitures were also considered during our simulation. Based on the time domain ray tracing method, the UWB signal propagation characteristics such as received power distribution, root mean square delay spread, multipath arrive delay distribution parameters were also discussed under line-of-sight and non-line-of-sight propagation. The analysis results provided deployment basis of UWB signal under the indoor environment, which benefit to research and develop technology for indoor Internet of Things.

A Mathematical Framework to Evaluate Flexible Outdoor User Association in Urban Two-Tier Cellular Networks

In this paper, we present a mathematical framework to evaluate the performance of a typical outdoor user in an urban two-tier mobile network under a biased user association. The urban environment is abstracted by a Boolean scheme of blockages, which affects the deployment of outdoor base stations (BSs) and indoor small cell BSs, and the signal propagation characteristics of the wireless channels. A building is served by an indoor small cell BS with a certain probability, which we denote as occupation probability. Employing tools from stochastic geometry, we derive mathematical expressions for the coverage probability and the average spectral efficiency of a typical outdoor user. Numerical evaluations are carried out with the third generation partnership project compliant outdoor BS scenarios. Our results show that the increasing blockage density has a negative impact on the spectral efficiency in sparse outdoor BSs scenarios, but it has a positive impact on the performance of the network in dense outdoor BSs scenarios. We build our analysis on several assumptions, which are verified by extensive Monte Carlo simulations.

Collaborative Indoor Access Point Localization Using Autonomous Mobile Robot Swarm.

Localization of access points has become an important research problem due to the wide range of applications it addresses such as dismantling critical security threats caused by rogue access points or optimizing wireless coverage of access points within a service area. Existing proposed solutions have mostly relied on theoretical hypotheses or computer simulation to demonstrate the efficiency of their methods. The techniques that rely on estimating the distance using samples of the received signal strength usually assume prior knowledge of the signal propagation characteristics of the indoor environment in hand and tend to take a relatively large number of uniformly distributed random samples. This paper presents an efficient and practical collaborative approach to detect the location of an access point in an indoor environment without any prior knowledge of the environment. The proposed approach comprises a swarm of wirelessly connected mobile robots that collaboratively and autonomously collect a relatively small number of non-uniformly distributed random samples of the access point’s received signal strength. These samples are used to efficiently and accurately estimate the location of the access point. The experimental testing verified that the proposed approach can identify the location of the access point in an accurate and efficient manner.