Position Of Transmitter Research Articles

Geodetic VLBI with an artificial radio source on the Moon: a simulation study

We perform extensive simulations in order to assess the accuracy with which the position of a radio transmitter on the surface of the Moon can be determined by geodetic VLBI. We study how the quality and quantity of geodetic VLBI observations influence these position estimates and investigate how observations of such near-field objects affect classical geodetic parameters like VLBI station coordinates and Earth rotation parameters. Our studies are based on today’s global geodetic VLBI schedules as well as on those designed for the next-generation geodetic VLBI system. We use Monte Carlo simulations including realistic stochastic models of troposphere, station clocks, and observational noise. Our results indicate that it is possible to position a radio transmitter on the Moon using today’s geodetic VLBI with a two-dimensional horizontal accuracy of better than one meter. Moreover, we show that the next-generation geodetic VLBI has the potential to improve the two-dimensional accuracy to better than 5 cm. Thus, our results lay the base for novel observing concepts to improve both lunar research and geodetic VLBI.

MCMC Methods for Realistic Indoor Wireless Optical Channels Simulation

This paper presents two new simulation algorithms of the optical wireless channel based on the Markov Chain Monte Carlo method. They allow to generate correlated three-dimensional light paths, keeping into account the nature of the simulation environment, taking advantage of its complexity such as transmitter and receiver position and orientation, the geometry, and the nature of the surfaces (diffuse, specular, etc.). Like Markov Chain Monte Carlo methods, these new algorithms are adaptive. They automatically do more calculation where light paths transport more power. Hence, they optimize their convergence speed, reducing the required number of paths to achieve a given accuracy threshold for the channel impulse response calculation. This paper shows that, compared to previous classical Monte Carlo solutions, these new algorithms reduce the computation time, up to a factor 225 for a fixed quality according to our experiments.

Three-Dimensional Modeling of TDEM Study for Carbon Capture Storage

TDEM (Time Domain Electromagnetic) method is a sounding geophysical method using electromagnetic wave generated by the electrical current source to image cross section of earth’s subsurface. TDEM using galvanic source (grounded wire) is one of TDEM acquisition technique which has flexible properties for the complex topography of measurement area. Three-dimensional forward and inversion modeling technique of TDEM with galvanic source still develops until now. Three-dimensional modeling is required because three-dimentional structure can influence TDEM signal which has a dimension of z-axis direction only. In this paper, We have been developing a 3D forward modeling program applying finite difference time domain method for 3D subsurface models. We can assess a distribution of TDEM synthetic data affected by 3D model. Using this 3D TDEM modeling program synthetic data has been generated as the function of transmitter and receiver position in 3D model space. Furthermore, this program can be used to simulate a conductivity change of reservoir model as consideration of reservoir monitoring implementation.

Improved electromagnetic tracking for catheter path reconstruction with application in high-dose-rate brachytherapy.

Electromagnetic (EM) catheter tracking has recently been introduced in order to enable prompt and uncomplicated reconstruction of catheter paths in various clinical interventions. However, EM tracking is prone to measurement errors which can compromise the outcome of the procedure. Minimizing catheter tracking errors is therefore paramount to improve the path reconstruction accuracy. An extended Kalman filter (EKF) was employed to combine the nonlinear kinematic model of an EM sensor inside the catheter, with both its position and orientation measurements. The formulation of the kinematic model was based on the nonholonomic motion constraints of the EM sensor inside the catheter. Experimental verification was carried out in a clinical HDR suite. Ten catheters were inserted with mean curvatures varying from 0 to [Formula: see text] in a phantom. A miniaturized Ascension (Burlington, Vermont, USA) trakSTAR EM sensor (model 55) was threaded within each catheter at various speeds ranging from 7.4 to [Formula: see text]. The nonholonomic EKF was applied on the tracking data in order to statistically improve the EM tracking accuracy. A sample reconstruction error was defined at each point as the Euclidean distance between the estimated EM measurement and its corresponding ground truth. A path reconstruction accuracy was defined as the root mean square of the sample reconstruction errors, while the path reconstruction precision was defined as the standard deviation of these sample reconstruction errors. The impacts of sensor velocity and path curvature on the nonholonomic EKF method were determined. Finally, the nonholonomic EKF catheter path reconstructions were compared with the reconstructions provided by the manufacturer's filters under default settings, namely the AC wide notch and the DC adaptive filter. With a path reconstruction accuracy of 1.9mm, the nonholonomic EKF surpassed the performance of the manufacturer's filters (2.4mm) by 21% and the raw EM measurements (3.5mm) by 46%. Similarly, with a path reconstruction precision of 0.8mm, the nonholonomic EKF surpassed the performance of the manufacturer's filters (1.0mm) by 20% and the raw EM measurements (1.7mm) by 53%. Path reconstruction accuracies did not follow an apparent trend when varying the path curvature and sensor velocity; instead, reconstruction accuracies were predominantly impacted by the position of the EM field transmitter ([Formula: see text]). The advanced nonholonomic EKF is effective in reducing EM measurement errors when reconstructing catheter paths, is robust to path curvature and sensor speed, and runs in real time. Our approach is promising for a plurality of clinical procedures requiring catheter reconstructions, such as cardiovascular interventions, pulmonary applications (Bender et al. in medical image computing and computer-assisted intervention-MICCAI 99. Springer, Berlin, pp 981-989, 1999), and brachytherapy.

A Radio Transmitter for Quail

This paper describes a small radio-transmitter that has been developed specifically for use on quail. The transmitter weighs 5g, is disk-shaped (25mm diameter X 7mm thick) and is worn on the chest. It is kept in place by a harness made from nylon covered, stainless-steel wire that also functions as the antenna. Because of the transmitter's light weight, shape, and position, quail seem to tolerate it very well. Also, it cannot be seen by aerial predators. The nominal signal consists of 30 msec pulses with a frequency of 1 ha. Movement produces one extra 40 rnsec pulse per cycle, 500 msec after the 30 msec pulse. These characteristics allow for relatively simple automatic detection and recording of activity. The transmission range, using a commercially available 3-element Yagi and receiver, exceeds one-half mile. Life expectancy is about 60 days. Components for the transmitter cost about $25.00 (1981).

Wireless Capsule Gastrointestinal Endoscopy: Direction-of-Arrival Estimation Based Localization Survey.

One of the significant challenges in capsule endoscopy (CE) is to precisely determine the pathologies location. The localization process is primarily estimated using the received signal strength (RSS) from sensors in the capsule system through its movement in the gastrointestinal (GI) tract. Consequently, the wireless CE (WCE) system requires improvement to handle the lack of the capsule instantaneous localization information and to solve the relatively low transmission data rate challenges. Furthermore, the association among the capsule's transmitter position, capsule location, signal reduction, and the capsule direction should be assessed. These measurements deliver significant information for the instantaneous capsule localization systems based on time-of-arrival approach, phase difference of arrival, RSS, electromagnetic, direction of arrival (DOA), and video tracking approaches are developed to locate the WCE precisely. This review introduces the acquisition concept of the GI medical images using the endoscopy with a comprehensive description of the endoscopy system components. Capsule localization and tracking are considered to be the most important features of the WCE system, thus this paper emphasizes the most common localization systems generally, highlighting the DOA-based localization systems and discusses the required significant research challenges to be addressed.

Positioning Using Terrestrial Multipath Signals and Inertial Sensors

This paper extends an algorithm that exploits multipath propagation for position estimation of mobile receivers named Channel-SLAM. Channel-SLAM treats multipath components (MPCs) as signals from virtual transmitters (VTs) and estimates the positions of the VTs simultaneously with the mobile receiver positions. For Channel-SLAM it is essential to obtain angle of arrival (AoA) measurements for each MPC in order to estimate the VT positions. In this paper, we propose a novel Channel-SLAM implementation based on particle filtering which fuses heading information of an inertial measurement unit (IMU) to omit AoA measurements and to improve the position accuracy. Interpreting all MPCs as signals originated from VTs, Channel-SLAM enables positioning also in non-line-of-sight situations. Furthermore, we propose a method to dynamically adapt the number of particles which significantly reduces the computational complexity. A posterior Cramér-Rao lower bound for Channel-SLAM is derived which incorporates the heading information of the inertial measurement unit (IMU). We evaluate the proposed algorithm based on measurements with a single fixed transmitter and a moving pedestrian carrying the receiver and the IMU. The evaluations show that accurate position estimation is possible without the knowledge of the physical transmitter position by exploiting MPCs and the heading information of an IMU.

Deployment methods of visible light communication lights for energy efficient buildings

Indoor visible light communication (VLC) uses light emitting diodes (LEDs) to provide both illumination and data communication. The deployment of LED plays an important role in maintaining a steady optical power distribution over the reference receiving plane. Typical ways of luminaire deployment in offices and homes are not optimized for VLC. This paper investigates various configurations of LEDs for deploying them on the ceilings of offices and homes. The existing square array deployment of LEDs does not provide a full coverage on the receiving plane leaving dead spaces, which in turn affects the performance of the whole system. An optimized circular deployment scheme is proposed that considers both the position of the LED transmitters on the ceiling and the first reflections at each wall to yield more accurate results. Rectangular deployment and circular deployment are analyzed through simulation of the received optical power distribution, average outage area rate, and energy consumption. An optimization technique is developed to analyze the LED deployment schemes. It is clear from the results that the circular LED deployment provides a better performance than the square array grid LED deployment.

Tracing a Linearly Moving Node From Asynchronous Time-of-Arrival Measurements

We address the problem of estimating the position and velocity of a radio transmitter moving with constant (unknown) velocity from packet arrival timestamps collected by a set of anchor nodes in fixed known positions. The considered system is completely asynchronous: no assumption is made about node clock synchronization nor about timing of transmitted packets. A distinguishing feature of the proposed model is that it relies exclusively on reception timestamps, with no need to measure nor control transmission times. Because of that, transmitters do not need to cooperate to the tracing process, enabling the opportunistic exploitation of packets that were generated for communication (not localization) purposes. We consider a batch processing approach, where all the measurements collected within a given observation window are jointly processed. Different generalized least squares formulations are provided for the problem at hand and their equivalence is proved.

Multipath Assisted Positioning with Simultaneous Localization and Mapping

This paper describes an algorithm that exploits multipath propagation for position estimation of mobile receivers. We apply a novel algorithm based on recursive Bayesian filtering, named Channel-SLAM. This approach treats multipath components as signals emitted from virtual transmitters, which are time synchronized to the physical transmitter and static in their positions. Contrary to other approaches, Channel-SLAM considers also paths occurring due to multiple numbers of reflections or scattering as well as the combination. Hence, each received multipath component increases the number of transmitters resulting in a more accurate position estimate or enabling positioning when the number of physical transmitters is insufficient. Channel-SLAM estimates the receiver position and the positions of the virtual transmitters simultaneously; hence, the approach does not require any prior information, such as a room-layout or a database for fingerprinting. The only prior knowledge needed is the physical transmitter position as well as the initial receiver position and moving direction. Based on simulations, the position precision of Channel-SLAM is evaluated by a comparison to simplified algorithms and to the posterior Cramer-Rao lower bound. Furthermore, this paper shows the performance of Channel-SLAM based on measurements in an indoor scenario with only a single physical transmitter.

Relief geometric effects on frequency-domain electromagnetic data

A perpendicular transmitter-receiver coils arrangement used in the frequency-domain electromagnetic survey can have deviations in relation to its standard geometric definition due to the relief geometry of the surveyed area when combined with large transmitter-receiver distance and large transmitter loop size. This happens because the local relief characteristics along the transmitter loop wire laid on the ground can deviate the equivalent magnetic moment axis from the vertical, and the global characteristics locate the transmitter and receiver positions at different elevations. A study about that is carried on here substituting the rugged relief by an inclined plane. We have developed a new formulation for the [Formula: see text]-layered model that allowed us to investigate the relief geometry effects on FDEM data but restricting the analysis to the two-layer earth model, considering three cases of transmitter-receiver situations controlled by the relief conditions. The curves representing the Argand diagram and the apparent polarization parameter as a function of the apparent induction number were obtained for each relief model. Such procedures resulted to be very useful to demonstrate their behavior departing from those curves obtained for an inclined and a horizontal ground. These results show that small deviations in the verticality of the transmitter loop axis or in the horizontality of the surficial plane causes significant deviations, even for angles as small as 1°.

The effect of dielectric permittivity on the fields radiated from a radio-frequency electric dipole in a homogeneous whole space

The radio imaging method (RIM) is an electromagnetic cross-borehole method with applications in mineral exploration, as well as in the coal industry, where it is used across mine drives. Attenuation of the signal from conductive regions may indicate areas of mineralization, and these conductive effects in general dominate the response. In an effort to better understand the effect of a material’s dielectric permittivity on the response of the RIM, we have developed a simple program to model an electric dipole in a homogeneous whole space. When increasing the dielectric permittivity, the amplitude peak broadened and increased, whereas the phase peak sharpened and shifted negatively. To showcase the effect of dielectric permittivity on RIM data, data recorded from two transmitter positions in a moderately homogeneous zone in the Sudbury Basin were curve fit, and we concluded that despite the stronger effect that conductivity has on the signal, RIM is still sensitive to dielectric permittivity, and appropriate values must be used when developing conductivity tomograms. In addition, we found that for the given situation and frequencies used, an increase in either the conductivity or dielectric permittivity could be accounted for by a decrease of approximately the same factor in the other variable. However, the low-conductivity, high-permittivity case seemed to fit the shape of the amplitude and phase curves better. For the sulfide impregnated crystalline rocks at our field site, relative dielectric constants of 26.4 and 31 at 1250 and 625 kHz, respectively, were inferred.

A Green Geographic Routing in Wireless Sensor Network

The routing information is hard to maintain and the energy is limited in highly dynamic wireless sensor network. To solve these problems, energy-saving geographic routing (ESGR) is proposed, which does not maintain the network topology and can save energy. A node broadcast its position information to its neighboring nodes before transmitting data. The neighboring nodes compute the position of the virtual relay node using the data transmitter position, the base station position and the energy consumption for circuits and propagation. The neighboring nodes determine whether to become the relay node through competition based on its position, the destination position and the virtual relay node position. The neighboring nodes compute the delay time distributedly according to the competition strategy. The neighboring node with the shortest delay time can respond to the data sender first and become the sole relay node. The handshake mechanism efficiently prevents the collision among the neighboring nodes during competition, which is of high communication efficiency. When a routing hole is found, the relay region is changed and an approaching destination relay strategy is adopted, which reduces the impact of routing holes. The simulation shows that the proposed algorithm is better than BLR, because of the lower energy consumption and lower packet loss ratio. The ESGR algorithm is more appropriate for highly dynamic wireless network.

Analysis of Radio Wave Propagation in an Urban Environment and its Application to Initial Disaster Response Support

When disasters strike, it is important to quickly collect and analyze disaster-related information immediately after the event. We have suggested ZigBee and geographic information systems (GIS) technologies to resolve these problems and provide an effective communications system. In this paper, a method for the rapid setup of short-range wireless networks infrastructure, which estimates the radio wave propagation and optimizes the positions of transmitters is proposed. Our estimation method is experimentally verified, and it combines ray-tracing with preliminarily obtained statistical attenuation information, which allows us to consider different types of the land and its elevation. Thus, we can determine the effective ranges for radio communication for each potential location in the actual environment. This information is then used in our optimization procedure to reduce the number of transmitters needed to establish connections.

A multiple transmitter and receiver electromagnetic system for improved target detection

We have developed an alternative strategy for the inevitable deeper inductive electromagnetic (EM) exploration, which will be required as shallow deposits are exhausted. Rather than using very large magnetic moment ground loops, measurement stations are repeated using many smaller sized loops with smaller moments. The multiple transmitter data are then weighted and summed into a single high signal-to-noise ratio (S/N) composite transmitter. The composite transmitter can be thought of as a postprocessing method that uses the collected multitransmitter data to construct/simulate a transmitter, which maximizes the coupling to a particular target. The appropriate transmitter weights to use will depend on the target location and geometry, and, as such, different weighting schemes allow for the construction of different composite transmitters, each of which will maximally highlight different targets. We have assumed no prior knowledge of the location and orientation of the exploration targets, and we constructed composite transmitters for each possible location of a discretized subsurface and 324 possible target orientations (dipole embedded within a fully resistive medium). A modified difference of squares and a dipole look-up table was used to assess the fit between each composite transmitter and the suggested target location and orientation. Synthetic studies using conductive plate target(s) embedded within a fully resistive medium found that the target locations and orientations could be accurately determined and that the S/N of the composite transmitter was significantly higher than that of standard fixed-loop ground and airborne surveys. In a ground time-domain EM field test, 23 transmitter positions were used, and a shallow target (conductive dike) could be identified using the developed methodology. The composite transmitter data we produced was considerably easier to interpret and had a larger amplitude than that of any one single transmitter.

Inside-Out Propagation: Developing a Unified Model for the Interference in 5G Networks

This article presents a generalized indoor-to-outdoor signal propagation model based on ray-tracing and exhaustive measurements campaign with the aim of developing a unified model for the interference in fifth-generation (5G) networks with femtocells underlying macrocells. It considers large buildings and typical residential houses. The objective is to capture the complex effects of the architectural layout, fading, shadowing, and building materials as well as to develop a practical nonsite-specific composite model to be used in the interference analysis and planning of next-generation networks, where not all information about the position of the transmitters or the building layouts is available. To that end, many different floor plans are considered, and the positions of the indoor transmitter are changed randomly. The obtained results reveal that the signal attenuation in the outdoor environment can be best characterized by a Gaussian-mixture (GM) distribution model.

Statistical characterization of the 2.45 GHz propagation channel aboard trains

<p class="Abstract"><span lang="EN-US">The propagation channel aboard trains is investigated with reference to the propagation path loss within cars, the delay spread and the coherence bandwidth. Results show that the path loss exponent is slightly smaller than in free space, possibly due to reflections by metal walls, and that it does not depend significantly on the position of transmitter and receiver. The delay spread and coherence bandwidth depend on both the polarization and distance between transmitter and receiver while the effect of interaction is not statistically significant. The best fit for both delay spread’s and coherence bandwidth’s experimental distribution is also investigated. Results show that it does not always match models suggested in the literature and that the fit changes with the values of the input parameters. Finally, the functional law between coherence bandwidth and delay spread is determined. Results typically match expectations although the specific measurement configuration effects the model parameters.</span></p>

SISTEM DETEKTOR ARAH SINYAL RF MENGGUNAKAN ANTENA DOPPLER

Two-Way Communication technology uses electromagnetic waves growing very rapidly. Various areas of public life, military and emergency purposes using the radio frequency spectrum, which would be very helpful. This communication system weakness, can not be used to emit a frequency along the same Waku. When this happens as a result of communication will be closed (jammed) for crowded frequency sometimes even no intent to disrupt a lot happening in the field of communication such as radio amateur frequencies. Directional Finder conventional radio has served for many years used to look for the direct nuisance frequency transmitter that has now been inefficient in terms of time and operations. Doppler system applications with Adaptive systems can be used as the basis for the work of Radio Stand Finder to detect the direction of the position of the RF transmitter without direct mobility. Roanoke Doppler antenna designed with a system of switching and amplifier signal reception by the arrangement of square-4 half-wavelength antenna that can determine the direction of the RF signal. Adaptive system can help lock the receiver system information is based on strong towards the greatest signal intensity.

Long‐duration geomagnetic storm effects on the D region of the ionosphere: Some case studies using VLF signal

AbstractThe present work investigates the effects of long‐duration geomagnetic storms on VLF signal during ionospheric sunrise time, commonly known as D Layer Preparation Time (DLPT) depth. The VLF signal at 19.8 kHz transmitted from Northwest Cape, Australia, and received at a low‐latitude station, Tripura, India, is used for the present analysis. The data for the analysis are selected from November 2008 to October 2011. In the active period of the geomagnetic storms, the average DLPT depth is found to have a negative correlation coefficient of 0.91 with geomagnetic Ap index. It is also found that with each 10 unit increase of Ap index, the DLPT depth (the day and night asymmetry level) changes by 1.25 dB. The results are supported with modeled International Reference Ionosphere (IRI) electron density data and DLPT depth at 71 km height for the three positions, namely, receiver position, signal hop position, and the transmitter position along the total Great Circle Path. It is found that the receiver position electron density is the main controlling factor for DLPT depth. The correlation between IRI electron density and DLPT depth increases from −0.13 at transmitter position to −0.33 at the first hop position, to −0.46 at the receiver position, respectively. The percentage change of post storm electron density, at 71 km height, is found to increase by more than 100% at the receiver position. The results are discussed on the basis of the electron density changes over the signal propagation path, mainly caused by the geomagnetic storms.

Efficient closed-form estimators for multistatic sonar localization

This paper addresses the multistatic sonar localization problem using time measurements only or with bearings in the presence of Gaussian transmitter positions, receiver positions, and propagation speed variations. We develop efficient algebraic solutions to this nonlinear estimation problem through parameter transformation and multistage processing. Both situations of known and unknown statistical distribution of the propagation speed are considered. Analysis supports their performance in reaching the hybrid Cramer-Rao lower bound (CRLB) over the small error region.