Receiver Positions Research Articles

GNSS Repeater Based Differential Indoor Positioning With Multi-Epoch Measurements

Global Navigation Satellite System (GNSS) based indoor positioning generally utilizes repeaters to amplify and retransmit the original GNSS signals to indoor receivers. To improve the positioning accuracy with GNSS repeaters in indoor environments such as an underground parking lot and an enclosed depot, in this paper, a carrier phase measurement based differential indoor positioning method is proposed. Without reference stations, the carrier phases measured by using the repeated signals are differenced between repeaters. Considering that upon carrier tracking loop locking the signals the carrier phase cycle integer ambiguity remains unchanged, the differenced phase measurements at two consecutive epochs are combined to find the receiver position. Receiver coordinates and phase cycle integer ambiguities are solved jointly with assistant Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) algorithm. High positioning accuracy is achieved by the proposed technique, and this is verified by close-to-reality simulations.

Retracted: GPS Receiver Position Estimation and DOP Analysis Using a New Form of the Observation Matrix Approximations

Retracted: GPS Receiver Position Estimation and DOP Analysis Using a New Form of the Observation Matrix Approximations

Real-time sound synthesis of pass-by noise: comparison of spherical harmonics and time-varying filters

This paper proposes and compares two sound synthesis techniques to render a moving source for a fixed receiver position based on indoor pass-by noise measurements. The approaches are based on the time-varying infinite impulse response (IIR) filtering and spherical harmonics (SH) representation. The central contribution of the work is a framework for realistic moving source sound synthesis based on transfer functions measured using static far-field microphone arrays. While the SHs require a circular microphone array and a free-field propagation (delay, geometric spread), the IIR filtering relies on far-field microphones that correspond to the propagation path of the moving source. Both frameworks aim to provide accurate sound pressure levels in the far-field that comply with standards. Moreover, the frameworks can be extended to additional sources and filters (e.g. sound barriers) to create different moving source scenarios by removing the room size constraint. The results of the two sound synthesis approaches are preliminary evaluated and compared on a vehicle pass-by noise dataset and it is shown that both approaches are capable of accurately and efficiently synthesize a moving source.

Map-Assisted Constellation Design for mmWave WDM With OAM in Short-Range LOS Environment

We consider a system that integrates positioning and single-user millimeter wave (mmWave) communication, where the communication part adopts wavelength division multiplexing (WDM) and orbital angular momentum (OAM). This paper addresses the multi-dimensional constellation design in short-range line-of-sight (LOS) environment, with stable communication links. We propose a map-assisted method to quantify the system parameters based on positions and reduce real-time computing overhead. We explore the possibility of using a few patterns in the maps, and investigate its performance loss. We first investigate the features of OAM beams, and find that the link gain ratio between any two sub-channels remains unchanged at some specific positions. Then, we prove that a fixed constellation can be adopted for the positions where the link gain matrices are sufficiently close to be proportional. Moreover, we prove that the system can adopt a fixed power vector to generate a multi-dimensional constellation if the difference between fixed power vector and optimal power vector is small. Finally, we figure out that the constellation design for all receiver positions can be represented by a few constellation sets.

Majorization-Minimization Method for Elliptic Localization in the Absence of Transmitter Position

This paper investigates the problem of elliptic localization in the absence of transmitter position. An efficient iterative method is developed to jointly evaluate the target and transmitter positions. Using the measurement information from the indirect paths reflected from the target and the direct paths between the transmitter and receivers, a non-convex maximum likelihood estimation (MLE) problem is formulated. Owing to the non-convex nature of the issue, we apply the majorization-minimization (MM) principle to address the MLE problem, which iteratively minimizes a convex surrogate function instead of the original objective function. Moreover, the proposed MM method is further extended to tackle a general scenario where both multiple unknown transmitters and receiver position errors are considered. Finally, numerical simulations demonstrate that the proposed MM method outperforms the state-of-the-art methods.

Removal of Intra-Array Statics in Seismic Arrays Due to Variable Topography and Positioning Errors

A receiver array is an arrangement of geophones used to enhance the signal-to-noise ratio (S/N) of seismic data. However, deviations from ideal array conditions can lead to the non-optimal performance of the array. This study investigates, quantitatively, the array performance in the presence of topographic variations and positioning errors using 2D seismic data acquired in eastern Saudi Arabia. A receiver array was laid over a sand dune with variable topography underlain by a flat sabkha that has a very shallow water table. The topographic variations and position errors were calculated from Differential Global Positioning System (D-GPS) measurements of source and receiver positions and elevations. The errors in receiver positions, measured relative to the ideal receiver spacing, gave a mean and standard deviation of about 0.35% and 1%, respectively. On the other hand, elevation errors (topographic variations) from a horizontal datum gave a mean and standard deviation of about 25% and 13%, respectively. The ideal array response was found by removing both elevation and position errors. The first-arrival energy of the array was calculated after removal of elevation and position errors separately and compared to the ideal-array energy. Comparison showed a 64% enhancement in the first-arrival energy after correcting for elevation errors alone and almost no enhancement after correcting for position errors alone. The proposed approach can be used to calculate accurate static corrections for seismic reflection processing and to generate high-resolution subsurface images for engineering applications.

Optical performance evaluation of a large solar dish/Stirling power generation system under self-weight load based on optical-mechanical integration method

Solar dish concentrator system is an optical device that provides high quality thermal source for thermodynamic devices such as Stirling heat engine, the structural deformation caused by self-weight load leads to change of mirror shape and receiver position, reducing its optical performance to affect the safe and efficient operation. In this paper, a previously developed large-scale 38 kW dish/Stirling system with 17.7 m diameter (XEM-Dish system) is used as object, an optical-mechanical integration model of XEM-Dish system is established by combining finite element method and ray-tracing method, which is used to evaluate the effects of self-weight on its optical performance at different elevation angles, including the results of mirror slope error and flux distribution, etc. A method of measuring the deformation of XEM-Dish system using Leica TS30 total station combined 360° prism is presented for validating the correctness of finite element model. Results show that the mirror slope error components SDx and SDy both increase with increase of elevation angle when only concentrator is deformed; mirror slope error increases with its deformation, but their distribution laws in different. The excellent optical efficiency 87% and flux distribution are maintained for XEM-Dish system under self-weight load, with SDx around 0.58 mrad at 0°–60° elevation angle.

Two‐port network compact representation of resonator arrays for wireless power transfer with variable receiver position

SummaryThis paper presents an equivalent circuit characterization of an array of resonators for wireless power transfer (WPT) applications. These apparatuses are composed of magnetically coupled resonant coils acting as a transmitter which feeds a receiver coil that can be placed over them at any position, allowing the tolerance of the system to the receiver misalignment to be dramatically enhanced. This advantage makes resonator arrays a suitable solution for both low‐ and high‐power applications. The latter usually involve battery charging, with the resonator array acting as a transformer stage, ensuring galvanic isolation. An equivalent two‐port network can be defined for any receiver position, allowing the array to be treated as a traditional transformer. Thereby, the simulation of the system can be simplified, as it is required in the design steps of a converter and control strategy. Analytical expressions of the two‐port network parameters are proposed for arrays of any size and length. The formulas have been numerically and experimentally validated.

Enhancing the performance of the Primary Surveillance Radar using Multilateration

One way to improve the measurements of the PSR (Primary Surveillance Radar) is to utilize the cinematic model of the aircraft (A/C) in a Kalman filter. Another newly developed method would be to implement multilateration using a large number of ground-based ADS-B (Automatic Dependent Surveillance-Broadcast) receivers. Originating in airport surveillance, multilateration grew to become the primary system for ATM (Air Traffic Management) in airspaces without PSR coverage. Given that each of the systems has its own advantages and limitations, we propose an evaluation of an alternative approach that uses data from multiple ADS-B receivers to implement a data fusion algorithm between PSR acquired position and MLAT (Multilateration) estimated position. Among the many ways to implement data fusion, have chosen to analyze two possible solutions: the direct fusion of the two available positions provided by the two systems using a traditional Kalman Filter and a linearization approach for the multilateration solution that does not require position computation. In both cases, these will improve the Kalman filter and lower the position estimation errors. The evaluation takes into consideration the possible sources of inaccuracies and provides sensibility analyses in regards to the number and positioning of ADS-B receivers involved in multilateration. This paper will conclude with a discussion of the computational power required for the two implementations.

Joint Light Planning and Error-Rate Prediction for Dual-Use Lighting/Visible Light Communication

We consider error-rate prediction for dual-use lighting systems with visible light communication (VLC) functionality. Since <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">light planning</i> rather than communications engineering is usually the driving discipline for practical dual-use settings, we extract VLC channel parameters as a by-product from advanced 3-dimensional (3D) light-planning models. By this means, we attain realistic signal-to-noise ratios for exemplary positions of a VLC receiver, which allows us to predict corresponding end-to-end bit error rates (BERs). Specifically, our procedure accounts for important aspects of state-of-art lighting systems, such as realistic light distribution curves of employed luminaires, possible presence unmodulated light sources, and, particularly, adaptive dimming operations in response to prevalent sunlight. In this paper, we (i) devise a methodology for VLC systems with optical receive filtering to convert photometric quantities into radiometric quantities, (ii) present examples of BER predictions for selected modulation schemes within some basic office environments, and (iii) conduct an analysis of the resulting simulation accuracy for a particular 3D light-planning tool. Simulation results show that our approach is indeed suited to predict realistic end-to-end BERs for dual-use lighting/VLC systems. Moreover, our procedure is fairly general and may be tailored to specific practical office settings and particular light plans of interest.

A review of Indoor Positioning Techniques

A great development has been appeared in wireless technologies and location based services and especially with appearance of open android operating system. In outdoor environments, Global Positioning System (GPS) can be used to get the position of smartphone users but GPS receiver is mostly inefficient in indoor environments. In this paper, several positioning systems have been reviewed which are used different technologies such as WLAN networks, cellular networks, infrared and ultrasound based system. Many comparison metrics between positioning techniques have been mentioned such as measurement type, accuracy, coverage, line of sight or non-line of sight, affected by multipath and cost and the best technique can be obtained through these metrics.

Random walk prediction-based channel model for underground-mining visible-light communication network

A random walk prediction (RWP)-based channel model is founded in the underground-mining (UM) visible-light communication (VLC) network. Among the factors that influence the communication performance of the UM-VLC network, the most significant ones are the arbitrary positioning and orientation of optical transmitters and receivers, tunnels with irregular walls, shadowing by machinery or miners, and scattering from dust clouds. This analysis allows for the development of a more realistic RWP-based channel model. These factors are integrated into a single-channel model that facilitates the derivation of complex expressions. The parameters are the received power of the RWP-based channel model, channel impulse response, root mean square delay spread, signal-to-noise-ratio, and bit error rate. The simulation results show that the RWP-based channel model meets the practical requirements better than other models in the reference papers.

Effects of receiving position and shell material on in-band full-duplex underwater communications' self-interference signal.

Despite the recent intensive research on adaptive algorithms for self-interference (SI) cancellation (SIC) in in-band full-duplex (IBFD) underwater acoustic communication (UWAC), there has been relatively little exploration of how the IBFD-UWAC modem shell affects the SI signal. This paper analyzes the effects of the shell material and the near-end receiver position on the SI signal. The analysis is done with a two-dimensional finite-element model in a free-field simulation environment, which combines the differential equation of motion and the time-dependent solver. The SI signal strength around the modem shell in the far-field conditions is obtained. The simulation and pool experiment results both show that (i) the strength of the received SI signal is lowest when the near-end receiver is on a line extending from the shell's geometric center perpendicularly to its central axis and (ii) a shell material with a high elastic coefficient is more conducive to suppressing the SI signal. A pool experiment showed that changing the spatial position of the near-end receiver and the shell material from aluminum to stainless steel enhanced the SIC performance of the IBFD-UWAC system by at least 12 and 4 dB, respectively.

Image-domain DAS 3D VSP elastic transmission tomography

SUMMARY Full-wavefield elastic imaging of active-source seismic data acquired by downhole receivers commonly offers higher-resolution subsurface images in the vicinity of a borehole compared to conventional surface seismic data sets, which can lack higher-frequency wavefield components due to longer travel paths and increased attenuation. An increasingly used approach for downhole acquisition is vertical seismic profiling (VSP), which has become more attractive when coupled with distributed acoustic sensing (DAS) using optical fibres installed in wells. The main difficulty for generating high-quality images with full-wavefield imaging tools for DAS VSP data, though, is the need for an accurate velocity model. To build plausible velocity models using active-source DAS VSP data, we adopt a 3-D image-domain elastic transmission tomography technique, originally developed for surface-recorded passive (microseismic) data, by exchanging the source and receiver positions (i.e. reciprocity) to mimic a passive-seismic surface monitoring scenario. The inversion approach exploits various images for each source constructed through time-reverse imaging (TRI) of downgoing P- and S-wave first-arrival waveforms. The TRI process uses the kinetic term of the (extended) PS energy imaging condition that exhibits sufficient sensitivity to velocity model errors. The method automatically updates the P- and S-wave velocity models to optimize image focusing via adjoint-state inversion. We illustrate the efficacy of the adopted elastic inversion technique using an active-source DAS 3-D VSP field data set acquired in the North Slope of Alaska. The numerical experiments demonstrate that the inverted elastic velocity models can be further used in full-wavefield acoustic/elastic imaging algorithms to obtain accurate subsurface images.

An Efficient Method to Compensate Receiver Clock Jumps in Real-Time Precise Point Positioning

In global navigation satellite systems (GNSSs)-based positioning, user receiver clock jump is a common phenomenon on the low-cost receiver clocks and can break the continuity of observation time tag, carrier phase and pseudo range. The discontinuity may affect precise point positioning-related parameter estimation, including receiver clock error, position, troposphere and ionosphere parameters. It is important to note that these parameters can be used for timing, positioning, atmospheric inversion and so on. In response to this problem, the receiver clock jumps are divided into two types. The first one can be expressed by the carrier phase and pseudo range having the same scale jump, and the second one is that they are having different scale jumps. For the first type, if a small priori variance of receiver clock error is provided, it can affect the accuracy of ionospheric delay estimation both in static and kinematic mode, while in the latter mode, it also affects position estimation. However, if large process noise is provided, numerical problems may arise since other parameters’ process noises are usually small, it is proposed to use the single point positioning with pseudo ranges to provide a priori value of receiver clock error, and an empiric value is assigned to its prior variance, this handle can avoid the above problems. For the second type, instead of compensating so many raw observations in the traditional methods, it is proposed to compensate the ambiguities at the clock jump epochs only in a new method. The new method corrects the Melbourne–Wubbena (MW) combination firstly in order to avoid the misjudging of cycle slips for current epoch, and the second step is to compensate the corresponding ambiguities, then, after Kalman filtering, the MW and its mean should be corrected back in order to avoid the misjudging of cycle slips at the next epoch. This approach has the advantage of handling the clock jump epoch-wise and can avoid correcting the rest of the observations as the traditional methods used to. With the numerical validation examples both in static and kinematic modes, it shows the new method is simple but efficient for real time precise point positioning (PPP).

Global Navigation Satellite System Real-Time Kinematic Positioning Framework for Precise Operation of a Swarm of Moving Vehicles.

The global navigation satellite system (GNSS) real-time kinematic (RTK) technique is used to achieve relative positioning centimeter levels among multiple agents on the move. A typical GNSS RTK estimates the relative positions of multiple rover receivers with respect to a single-base receiver. In a fleet of rover GNSS receivers, this approach is inefficient because each rover receiver only uses GNSS measurements of its own and those sent from a single-base receiver. In this study, we propose a novel GNSS RTK framework that facilitates the precise positioning of a swarm of moving vehicles through the GNSS measurements of multiple receivers and broadcasts fixed-integer ambiguities of GNSS carrier phases. The proposed framework not only provides efficient RTK positioning but also reliable performance with a limited number of GNSS satellites in view. Our experimental flight tests with six GNSS receivers showed that the systematic procedure of the proposed framework could maintain lower than 6 cm of 3D RMS positioning errors, whereas the conventional RTK failed to resolve the correct integer ambiguities of double difference carrier phase measurements more than 13% in five out of nine total baselines.

Sonic boom measurements: Practical implications considering ground effects, microphone installation, and weather hardening.

Sonic boom measurements from recent flight tests have provided an opportunity to investigate effects of microphone installation on sonic boom waveforms, spectra, and metric levels in support of NASA X-59 flight test planning. While those flight tests used N-wave aircraft (F-18s), modeling studies were also conducted using source characteristics for a shaped low-boom aircraft. Of particular interest were the effects of receiver height on boom waveforms and metrics at elevated receiver positions, microphone installation, and local ground cover type. Reductions of more than 2 dB in A-weighted sound exposure level and perceived level were shown for 1.6 ft (0.48 m) microphone heights for 35º ray elevation angle. Measured and modeled results are described in this letter.

In-situ measurement of the acoustic performance of a nearly-enclosed barrier prototype on an existing line in the urban rail transit system

The acoustic performance of a nearly-enclosed prototype meant to attenuate urban rail transit (URT) noise was measured in situ on an existing line. The prototype is constructed on a viaduct on Line 1, Ningbo, China, with a 2-meter-wide opening at the top. A series of measurements while trains passed by were carried out with twelve receiver positions at the site without and with the prototype. Train speeds were measured using a piezoelectric acceleration sensor located on a rail foot. By correcting pass-by levels for train speed, the measured results show that the nearly-enclosed prototype provides an attenuation with a maximum of 17 dB(A), and a minimum of 6 dB(A). One-third octave band spectrum analysis shows that the insertion loss specific to rolling noise yields on average more than 15 dB. Furthermore, comparisons between measured and predicted results by using 2.5-D boundary element method (2.5-D BEM) show that both of the employed PC and PMMA sheets could not provide sufficient transmission loss for the prototype in a real situation. Nevertheless, the nearly-enclosed prototype is effective against rolling noise for the URT system.

GPS Receiver Position Estimation and DOP Analysis Using a New Form of the Observation Matrix Approximations

A location sensor is a feature that communicates with a Global Positioning System (GPS) receiver to learn about the status of the current location. This work presents the GPS receiver position estimation and Dilution of Precision (DOP) analysis using a new approximate form of observation matrix which can be used in place of the classic observation matrix that was derived from the Taylor’s series. It has been realized that, the approximate observation matrix is numerically stable and provides greater precision in calculating DOP values and estimating the position of a GPS receiver. The experimental results show that the proposed observation matrix provides better precision in DOP analysis and GPS receiver position estimation with a fast convergence rate and improved algorithm stability. Therefore, it can be concluded that the proposed new observation matrix plays a significant role to estimate accurately the location of the GPS receiver position and to enhance all parameters of the DOP.

The effects of receiver arrangement on velocity analysis with multi‐concurrent receiver GPR data

AbstractDetermining subsurface electromagnetic (EM) wave velocity is critical for ground‐penetrating radar (GPR) data analysis, as velocity is used for the time‐to‐depth conversion, and hence leads to obtaining the precise location of the objects of interest. Currently, the way to acquire detailed subsurface EM wave velocity models involves employing multi‐offset GPR surveys, such as wide‐angle reflection‐refraction (WARR), in conjunction with normal moveout (NMO) based velocity analysis. Traditionally, these surveys are carried out using two separate transducers and were, therefore, time‐consuming and had limited uptake. Recent advances in GPR hardware have allowed the development of novel systems with multi‐concurrent sampling receivers, which enable rapid and dense acquisition of WARR data. These additional receivers increase the overall size, weight and cost of the system. Therefore, we investigated the effects of receiver arrangement on NMO‐based velocity analysis and considered reducing the overall number of transducers, whilst maintaining satisfactory velocity spectra resolution and, hence, obtaining detailed stacking velocity models as well as improved stacked reflection sections. We used both simulated data from complex three‐dimensional models as well as field data and examined different numbers and positions of receivers in different environments. Our results show that velocity spectra resolution can be maintained within acceptable limits whilst reducing the number of receivers from a configuration with seven equally spaced receivers, to a sparse configuration of four receivers. Thus, being able to decrease the number of receivers used by these new GPR systems will reduce both the total system weight and cost and, hopefully, increase their adoption for GPR surveys.