Station Positions Research Articles

Joint Beamforming Design and User Clustering Algorithm in NOMA-Assisted ISAC Systems.

To enhance the performance of non-orthogonal multiple access (NOMA)-assisted integrated sensing and communication (ISAC) systems in multi-user distributed scenarios, an improved Gaussian Mixture Model (GMM)-based user clustering algorithm is proposed. This algorithm is tailored for ISAC systems, significantly improving bandwidth reuse gains and reducing serial interference. First, using the Sum of Squared Errors (SSE), the algorithm reduces sensitivity to the initial cluster center locations, improving clustering accuracy. Then, direction weight factors are introduced based on the base station position and a penalty function involving users' Euclidean distances and sensing power. Modifications to the EM algorithm in calculating posterior probabilities and updating the covariance matrix help align user clusters with the characteristics of NOMAISAC systems. This improves users' interference resistance, lowers decoding difficulty, and optimizes the system's sensing capabilities. Finally, a fractional programming (FP) approach addresses the non-convex joint beamforming design problem, enhancing power and channel gains and achieving co-optimizing sensing and communication signals. The simulation results show that, under the improved GMM user clustering algorithm and FP optimization, the NOMA-ISAC system improves user spectral efficiency by 4.3% and base station beam intensity by 5.4% compared to traditional ISAC systems.

Autonomous Lunar Rover Localization while Fully Scanning a Bounded Obstacle-Rich Workspace.

This article addresses the scanning path plan strategy of a rover team composed of three rovers, such that the team explores unknown dark outer space environments. This research considers a dark outer space, where a rover needs to turn on its light and camera simultaneously to measure a limited space in front of the rover. The rover team is deployed from a symmetric base station, and the rover team's mission is to scan a bounded obstacle-rich workspace, such that there exists no remaining detection hole. In the team, only one rover, the hauler, can locate itself utilizing stereo cameras and Inertial Measurement Unit (IMU). Every other rover follows the hauler, while not locating itself. Since Global Navigation Satellite System (GNSS) is not available in outer space, the localization error of the hauler increases as time goes on. For rover's location estimate fix, one occasionally makes the rover home to the base station, whose shape and global position are known in advance. Once a rover is near the station, it uses its Lidar to measure the relative position of the base station. In this way, the rover fixes its localization error whenever it homes to the base station. In this research, one makes the rover team fully scan a bounded obstacle-rich workspace without detection holes, such that a rover's localization error is bounded by letting the rover home to the base station occasionally. To the best of our knowledge, this article is novel in addressing the scanning path plan strategy, so that a rover team fully scans a bounded obstacle-rich workspace without detection holes, while fixing the accumulated localization error occasionally. The efficacy of the proposed scanning and localization strategy is demonstrated utilizing MATLAB-based simulations.

GCMEbox: A MATLAB toolbox for extracting and analyzing common-mode errors from GNSS time series

High-precision global navigation satellite system (GNSS) time series data contain rich tectonic and non-tectonic motion information. However, such data also have common-mode errors (CME) related to spatiotemporal characteristics. CME will produce bias in accurate and reliable GNSS station positions and velocities estimations, ultimately deciphering erroneous geophysical signals. Currently, CME extraction methods can be divided into three categories: regional stack filtering, reference frame filtering, and statistical signal decomposition. The third method is widely used in geodetic data processing, including GNSS time series analysis, global time-varying gravity signal extraction, interferometric synthetic aperture radar (InSAR) time series analysis, etc. The demand for GNSS time series analysis software with interactive, visualization, and multifunctional features has also increased with the increase in GNSS stations. Therefore, we developed gCMEbox based on MATLAB. The gCMEbox’s primary functions include GNSS time series preprocessing, multiple statistical signal decomposition algorithms for extracting CME, GNSS time series analysis, visualization, velocity field construction, and generation of multiple time series post-processing products. Based on GNSS time series data, this study utilized the gCMEbox for data preprocessing, including format conversion, outlier removal, missing data recovery, etc. By applying statistical signal decomposition methods, gCMEbox successfully extracted CME. The primary objective of this study is to share this toolbox with the scientific community, providing a comprehensive tool for GNSS time series analysis and applications.

The analysis of the scatters of the filtered residuals of the GNSS stations from the crustal movement observation network of China

Through the analysis of the coordinate time series of the stations in the Crustal Movement Observation Network of China (CMONOC) from 2011 to 2019, it is found that the daily network scatters of the filtered residuals (called as SFR) of the station coordinate time series have obvious seasonal variation characteristics which reaches a maximum during summer and a minimum during winter. This phenomenon has not yet been further explained. Our analysis results demonstrate that the seasonal pattern of the daily SFR solutions is the temperature-dependent, such as small-scale atmospheric perturbation. The pattern of SFR series of the difference between the zenith wet delay (ZWD) calculated with GPS data and that calculated with meteorological data is similar to the SFR solutions computed using GPS data. The results mean that the estimated ZWD using GPS data does not fully capture the total real atmospheric variation. The atmospheric delay model in current GNSS analysis can effectively solve large-scale atmospheric delay estimation, but it may fail to deduct certain small-scale atmospheric disturbances. We think that a considerable portion of these small-scale disturbances are absorbed by the estimates of station positions.

INVESTIGATION OF THE EFFECT OF ANNUAL AVERAGE TEMPERATURE AND PRECIPITATION CHANGES ON CORS-TR STATIONS: THE CASE OF KSTM STATION

In this study, the effects of meteorological changes on the point positioning of CORS-TR stations were investigated. For this purpose, KURU, SINP, BOYT, CORU, CANK, CMLD, KRBK, KSTM stations were selected. The KSTM station was taken as unknown and adjusted based on other stations. Seasonal normal values of KSTM station in Kastamonu province covering the years 2016-2020 were examined in terms of temperature and precipitation amount. These values were determined according to the minimum, maximum and average value criteria by using Türkiye State Meteorological Service data. For the calculations, IGS-standardized RINEX data of the stations for 5 years and 12 months between 2016 and 2020 and for 10 days on the 11th and 20th days of each month were used. All calculations were processed with Leica Geo Office v8.x. The calculated coordinates were compared with the current coordinates of CORS-TR at the same epoch and examined according to annual temperature and precipitation. In the analyzes, it was tested by statistical method whether all measurements were compatible. When it was examined whether the temperature changes were statistically significant, it was observed that the test values were calculated according to the temperature changes were below the test distribution limit at 95% confidence interval. When it was examined whether the precipitation changes were statistically significant, it was observed that the test values were calculated according to the precipitation changes were below the test distribution limit at 95% confidence interval.

Modeling random isotropic vector fields on the sphere: theory and application to the noise in GNSS station position time series

Modeling random isotropic vector fields on the sphere: theory and application to the noise in GNSS station position time series

On the Integration of VLBI Observations to GENESIS into Global VGOS Operations

The upcoming European Space Agency (ESA) satellite mission GENESIS is an Earth-orbiting satellite carrying instruments of all four space geodetic techniques. The onboard transmitter for Very Long Baseline Interferometry (VLBI) will allow the observation of the satellite with VLBI radio telescopes. The objective of this study is to investigate the integration of VLBI observations of GENESIS into the operations of the VLBI Global Observing System (VGOS). Based on both current and foreseeable modern VGOS antenna networks, we consider the realistic observability of both geodetic radio sources and GENESIS. We conduct a comprehensive scheduling and perform extensive simulations of the VLBI observations. We assume that observations of GENESIS are scheduled within regular, geodetic experiments. The integration of GENESIS as an additional source in the scheduling results in a minimal degradation in the geodetic parameter estimation of station positions and dUT1 of less than 0.09 mm and 0.06 μs, respectively. The results suggest to schedule scans of GENESIS at intervals of about 5 min to limit the decrease in the number of observations of geodetic sources to less than 5% with respect to schedules containing only geodetic radio sources. The schedules for 24 h experiments comprise about 150 to 200 scans and 1000 to 5000 observations of GENESIS, depending on the size of the utilized network. The frame tie accuracy between the VLBI and GENESIS frames is assessed in the form of station positions, which are solely estimated from observations of GENESIS. Multiple 24 h experiments are simulated over 52 weeks with assumed session cadences of two to three experiments per week. By stacking the normal equations from three months of experiments, we obtain station position estimates with a precision of less than 10 mm. After 12 months, the repeatabilites are reduced to less than 5 mm.

On-board radar complex for high-precision direction finding of radio sources for autonomous guidance of winged UAVs

The subject of this article is the design of a cheap, simple, and highly accurate on-board radar system for determining the angular position of radio-signal emission stations, which can be used to guide UAVs to a specified area of space. The aim of this study is to develop high-precision functioning algorithms, practical recommendations for implementation, and experimental measurements of the main parameters of the onboard radio direction finders of radio radiation sources placed on winged UAVs. Objectives of the research: 1) analysis of the statistical theory of optimization of signal processing algorithms in radar systems; 2) synthesis of direction-finding algorithms for radio measurement sources capable of performing measurements with high accuracy and in a wide range of unambiguous measurement angles; 3) synthesis of the radio direction finder structural scheme and its simulation modelling; 4) design of radio direction finder receiving antennas capable of operating separately and in a complex; 5) justification of the choice of components for the input paths of receivers, parameters of ADC and microcomputers that make up the main components of the radar complex; 6) manufacturing of a working model of the radar complex; 7) experimental measurements in the laboratory. The methods for solving the tasks are based on the statistical theory of optimization of radio engineering systems for remote sensing and radar, existing software tools for simulation modelling, and the theory of radio measurements. The main idea behind creating a cheap, simple, and highly accurate on-board radar system for radio emitter direction finding is to combine the results of angular position measurements from several amplitude and phase meters. This approach allows us to create an easy-to-implement radio system with the advantages of different measuring instruments. The following results were obtained: 1) theoretical studies and simulation modelling confirmed that by combining measurements from a two-antenna amplitude direction finder with narrow diagrams, a two-antenna direction finder with wide diagrams, and a two-antenna phase finder, it is possible to achieve both high accuracy and a wide range of unambiguous measurements; 2) a radar system based on a cheap and commonly available element base was developed; 3) antennas were developed that can be easily installed under the wings of UAVs; 4) experimental studies confirmed the performance of complex signal processing in an on-board six-antenna radio direction finder. The material of this work forms the basis for further experimental development of radio-direction finders for various purposes, opens up opportunities for overcoming the contradiction between accuracy and range of unambiguous measurements, and highlights an additional direction for increasing the autonomy of winged UAVs.

MT-SIPP: An Efficient Collision-Free Multi-Chain Robot Path Planning Algorithm

Compared to traditional multi-robot path planning problems, multi-chain robot path planning (MCRPP) is more challenging because it must account for collisions between robot units and between the bodies of a chain and the leading unit during towing. To address MCRPP more efficiently, we propose a novel algorithm called Multi-Train Safe Interval Path Planning (MT-SIPP). Based on safe interval path planning principles, we categorize conflicts in the multi-train planning process into three types: travel conflicts, waiting conflicts, and station conflicts. To handle travel conflicts, we use an improved k-robust method to ensure trains avoid collisions with other trains during movement. To resolve waiting conflicts, we apply a time correction method to ensure the safety of positions occupied by trains during waiting periods. To address station conflicts, we introduce node constraints to prevent other trains from occupying the station positions of trains that have reached their target stations and are stopped. Experimental results on three benchmark maps show that the MT-SIPP algorithm achieves about a 30% improvement in solution success rate and nearly a 50% increase in the maximum number of solvable instances compared to existing methods. These results confirm the effectiveness of MT-SIPP in addressing the challenges of MCRPP.

Design of a Wind Tunnel Nozzle Section Trolley Control System Based on Backstepping Method

Abstract To accommodate different types of supersonic wind tunnel tests, frequent replacements of nozzle sections and test sections are required, involving multiple complex technical processes. To optimize operational procedures and improve efficiency, a control system for the wind tunnel nozzle section trolley based on the backstepping method was designed. The system uses radio frequency identification (RFID) signals for station positioning and intelligently adjusts the speed and direction of the control motor, thus driving the trolley to move back and forth automatically. Through the simulation of the motor motion control model, the system effectively reduces random disturbances in the motion system caused by load changes, achieves precise positioning of wind tunnel plugins and nozzle assemblies, enhances system operating accuracy, reduces production cycle times, and realizes a one-button positioning function for all components, playing a significant role in improving wind tunnel test efficiency and operational quality.

Localization Performance Analysis and Algorithm Design of Reconfigurable Intelligent Surface-Assisted D2D Systems.

The research on high-precision and all-scenario localization using the millimeter-wave (mmWave) band is of great urgency. Due to the characteristics of mmWave, blockages make the localization task more complex. This paper proposes a cooperative localization system among user equipment (UEs) assisted by reconfigurable intelligent surfaces (RISs), which considers device-to-device (D2D) communication. RISs are used as anchor points, and position estimation is achieved through signal exchanges between UEs. Firstly, we establish a localization model based on this system and derive the UEs' positioning error bound (PEB) as a performance metric. Then, a UE-RIS joint beamforming design is proposed to optimize channel state information (CSI) with the objective of achieving the minimum PEB. Finally, simulation analysis demonstrates the advantages of the proposed scheme over RIS-assisted base station positioning, achieving centimeter-level accuracy with a 10 dBm lower transmission power.

Vertical Accuracy of Google Earth Data

Digital Elevation Models (DEMs) are an important data source used in many engineering and Geographic Information System (GIS) applications. This paper illustrates a strategy for creating a DEM by utilizing elevation data from Google Earth and evaluating the vertical positional accuracy of the generated DEM adopting a well-defined methodology. To ensure the accuracy of the elevation data obtained from Google Earth, a thorough evaluation was done in three diverse small districts of the northern shoreline in Egypt. The evaluation process involved determining the ground coordinates of reference points utilizing two surveying techniques: total station and Real-Time Kinematic (RTK) Global Positioning System (GPS) surveys. These coordinates were compared with the ones predicated by the DEM generated by putting into service Google Earth's elevation data. Furthermore, the vertical accuracy was assessed using Shuttle Radar Topographic Mission (SRTM) data of Google Earth collected at two different periods in 2015 and 2023. The vertical accuracy of the Google Earth data is detailed utilizing Mean Error (ME), Maximum Absolute Error (MAE), and Root Mean Square Error (RMSE). According to the results, Google Earth's elevation data accuracy remains consistent from 2015 to 2023, and refining SRTM data does not improve the vertical accuracy. The vertical accuracy of the total station survey surpasses the one of the RTK GPS survey, and the elevation accuracy of the RTK GPS survey decreases with increasing height difference. In addition, the vertical accuracy of DEMs was found to be sufficient for some engineering applications but not accurate enough for precise engineering studies. The accuracy achieved in small height difference terrain can be utilized to produce large-scale cadastral maps, city plans, or land use maps. Finally, the elevation data offered by Google Earth can be utilized for preliminary studies at a low cost. However, to ensure the accuracy of these data, it is recommended that users compare them with reference data before implementation.

Efficient Fuzzy-Based 3-D Flying Base Station Positioning and Trajectory for Emergency Management in 5G and Beyond Cellular Networks

Efficient Fuzzy-Based 3-D Flying Base Station Positioning and Trajectory for Emergency Management in 5G and Beyond Cellular Networks

Charging change: Analysing the UK's electric vehicle infrastructure policies and market dynamics

Over the past decades, there has been a rapid adoption of electric vehicles (EVs) and a gradual reduction in the number of Gas Stations, aligning with carbon neutrality objectives. Major oil companies, like Shell, are transferring Gas Stations to Charging Stations, supported by UK government incentives to stimulate the charging infrastructure. This paper systematically investigates three key stakeholders: government, investors, and end-users, examining their interactions and the transition of stations, and evaluating the economic intrinsic competition relationships. Integrating the complex networks, it spatially represents the relative positions of stations and designates Gas Stations as potential future locations for Charging Stations. Meanwhile, this paper comprehensively analyses various policies targeting the UK market, applies dual market analysis to compare the simple and complex market structures among policy scenarios, emphasising the necessity for applying complex interactive markets in industrial evaluation. The findings reveal that direct policies targeting Charging Stations exert immediate and positive effects, while indirect policies targeting Gas Stations and consumers demonstrate marginal diminishing effects. Furthermore, subsidies on the EV prices are less effective compared with other policies, like construction subsidies, operation subsidies, etc., highlighting the need for targeted policy designs, to maximise the expansion and efficacy of EVs and Charging infrastructure.

A Comparative Analysis of Advanced Machine Learning Techniques for River Streamflow Time-Series Forecasting

This study examines the contribution of rainfall data (RF) in improving the streamflow-forecasting accuracy of advanced machine learning (ML) models in the Syr Darya River Basin. Different sets of scenarios included rainfall data from different weather stations located in various geographical locations with respect to the flow monitoring station. Long short-term memory (LSTM)-based models were used to examine the contribution of rainfall data on streamflow-forecasting performance by investigating five scenarios whereby RF data from different weather stations were incorporated depending on their geographical positions. Specifically, the All-RF scenario included all rainfall data collected at 11 stations; Upstream-RF (Up-RF) and Downstream-RF (Down-RF) included only the rainfall data measured upstream and downstream of the streamflow-measuring station; Pearson-RF (P-RF) only included the rainfall data exhibiting the highest level of correlation with the streamflow data, and the Flow-only (FO) scenario included streamflow data. The evaluation metrics used to quantitively assess the performance of the models included the RMSE, MAE, and the coefficient of determination, R2. Both ML models performed best in the FO scenario, which shows that the diversity of input features (hydrological and meteorological data) did not improve the predictive accuracy regardless of the positions of the weather stations. The results show that the P-RF scenarios yielded better prediction accuracy compared to all the other scenarios including rainfall data, which suggests that only rainfall data upstream of the flow monitoring station tend to make a positive contribution to the model’s forecasting performance. The findings evidence the suitability of simple monolayer LSTM-based networks with only streamflow data as input features for high-performance and budget-wise river flow forecast applications while minimizing data processing time.

Comprehensive Analysis on GPS Carrier Phase under Various Cutoff Elevation Angles and Its Impact on Station Coordinates’ Repeatability

When processing the carrier phase, the global navigation satellite system (GNSS) grants the highest precision for geodetic measurements. The analysis centers (ACs) from the International GNSS Service (IGS) provide different data such as precise clock data, precise orbits, reference frame, ionosphere and troposphere data, as well as other geodetic products. Each individual AC has its own strategy for delivering the abovementioned products, with one of the key elements being the cutoff elevation angle. Typically, this angle is arbitrarily chosen using generic values without studying the impact of this choice on the obtained results, in particular when very precise positions are considered. This article addresses this issue. To this end, the article has two key sections, and the first is to evaluate the impact of using the two different cutoff elevation angles that are most widely used: (a) 3 degrees cutoff and (b) 10 degrees cutoff elevation angle. This analysis is completed in two major parts: (i) the analysis of the root mean square (RMS) for the carrier phase and (ii) the analysis of the station position in terms of repeatability. The second key section of the paper is a comprehensive carrier phase analysis conducted by adopting a new approach using a mean of the 25-point average RMS (A-RMS) and the single-point RMS and using an ionosphere-free linear combination. By using the ratio between the 25-point average RMS and the single-point RMS we can define the type of scatter that dominates the phase solution. The analyzed data span a one-year period. The tested GNSS stations belong to the EUREF Permanent Network (EPN) and the International GNSS Service (IGS). These comprise 55 GNSS stations, of which only 23 GNSS stations had more than 95% data availability for the entire year. The RMS and A-RMS are analyzed in conjunction with the precipitable water vapor (PWV), which shows clear signs of temporal correlation. Of the 23 GNSS stations, three stations show an increase of around 50% of the phase RMS when using a 3° cutoff elevation angle, and only four stations have a difference of 5% between the phase RMS when using both cutoff elevation angles. When using the A-RMS, there is an average improvement of 37% of the phase scatter for the 10° cutoff elevation angle, whereas for the 3° cutoff elevation angle, the improvement is around 33%. Based on studying this ratio, four stations indicate that the scatter is dominated by the stronger-than-usual dominance of long-period variations, whereas the others show short-term noise. In terms of station position repeatability, the weighted root mean square (WRMS) is used as an indicator, and the results between the differences of using a 3° and 10° cutoff elevation angle strategy show a difference of −0.16 mm for the North component, −0.21 mm for the East component and a value of −0.75 mm for the Up component, indicating the importance of using optimal cutoff angles.

An integrated approach for sewage diversion: Case of the Huayuan mine, Hunan Province, China

Environment protection is a core priority for many governments in this century. Most environmental problems have diverse causes: emission of greenhouse gases from fossil fuels, resource depletion, or intense mining activities such as the Huayuan manganese mine. The positioning of mining factories and water treatment stations impacts the surrounding groundwater reservoir. As the mine expands, the environmental impact also increases, and the previous plan based on monitoring wastewater leakage has become inappropriate. Therefore, to solve this issue, a new study is required to understand the lateral resistivity distribution underground and to define a new station location for water treatment and divert the sewage to that station. In this study, the audio-frequency magnetotelluric method is used. Surveys of two long lines that cross the mining area to its boundaries are carried out. Data are robustly processed and inverted. Based on the inverted models, in addition to the geologic information, drilling inspections, and solid waste distributions map, the integrated interpretation develops two sites on the top of impermeable layers, which constitute a buffer point between the unsafe (high concentration of pollutants) and the safe zones in the northwestern part of the mine. From the resistivity distribution combined with the water quality analysis, a relationship between the fault structures reveals an interconnected conductive zone (CZ) in the southeastern part. As the main channels for water circulating underground, these CZs delineate the main groundwater reservoir with a clastic aquifer layer. However, close to factories, the water from faults contains solid wastes, thereby making the groundwater in that zone nonpotable, unlike the safety zone located in the northwestern part. This workflow can become a field guide to improve the environment of mines and the deployment of hydrogeologic drilling in a safe area.

Anatomy of the spatiotemporally correlated noise in GNSS station position time series

Anatomy of the spatiotemporally correlated noise in GNSS station position time series

Post-Pandemic Hiring Practices and Skills Requested by Local U.S. TV Stations

ABSTRACT Job ads are meant to capture the daily responsibilities of the position, as well as let candidates know the skills and qualities the right candidate for the job needs to demonstrate from the employer’s perspective. While Aupperle and Grzeslo (2020) studied job ads of legacy media stations, Deavours and Grzeslo (2020) were among the first to explore local broadcast television station job ads. Yet, after the “Great Resignation” following the COVID-19 pandemic, as well as recent technology and business model changes, researchers need to continue to update and monitor the rapidly evolving needs of local newsrooms. This study seeks to provide insight through a content analysis of job postings from U.S. local television stations, exploring the experience, skills, and experience requirements necessary to be competitive in today’s market, while also looking at how companies are working harder to attract talent. Using the theoretical lens of skills theory of leadership, the study also provides insight in hiring differences in station ownership, market size, and position type. Through content analysis of 349 job ads from 21 local news Designated Market Areas, findings suggest the field is embracing more convergent, digital reporting tactics, while still emphasizing the foundations of broadcast writing and visual storytelling. However, some of the most dramatic shifts in the industry toward innovation, emerging media, digital legal and ethical skills, and diversity are not reflected in job ads, creating little guidance for individuals and educators on how to prepare for an ever-changing job market.

The present strain rate of Quang Nam - Quang Ngai and the surrounding region

Studying the present strain rate is significant in determining the characteristics and origin of geological anomalies in the region. Tectonic strain occurs under the influence of various factors, especially tectonic forces, and only a few cases of deformation occur at speeds observable by humans. This research uses velocity data from GNSS measurements in Quang Nam - Quang Ngai and surrounding regions to assess present tectonic strain. The combination of methods used in this study includes calculating the ITRF Earth-fixed frame to minimize errors, the method of relative velocity calculation to compare the speed variations between station positions, and the deformation calculation method using the QOCA software developed by NASA's Jet Propulsion Laboratory (JPL). The calculated results show that the coastal areas of the study have relatively low strain rates with the principal strain rate <15 nano-strain/year, the magnitude of deformation is always less than 7.5 nano-strain/year, and the area is conducive to the development of dominant reverse faulting.