Regional Navigation Satellite System Research Articles

Analysis of Various Parameters of L5 and S1 NavIC Signals over Low Latitude Region

Abstract The NavIC/IRNSS (Navigation with Indian Constellation/ Indian Regional Navigation Satellite System) is an autonomous Indian based regional navigation system. The system is intended to provide navigation signals over the Indian region and 1500 kms around. It is necessary to evaluate the performance of NavIC system over the Indian region. In this paper various parameters (Tropospheric delay, C/No, Doppler frequency and vertical ionospheric delay) of the NavIC L5 and S1 signals are evaluated. The analysis is carried out for quiet (26th May, 2017) and disturbed days (28th May, 2017) over low latitude Hyderabad station (17.390 N, 78.310 E), India. The vertical ionospheric delay is the most considerable parameter of NavIC system. In this work, vertical ionospheric delay is estimated using single frequency global ionospheric models like Klobuchar and Grid models. The obtained results are compared with real time NavIC data for both L5 and S1 signals and the results are encouraging. The position accuracy parameters are also evaluated for L5 and S1 modes of receiver operation on a typical day (25th January, 2019). This work finds applications in development of single frequency NavIC receiver for civilian navigation applications.

Forecasting of ionospheric TEC for different latitudes, seasons and solar activity conditions based on OKSM

Ionosphere is the upper atmosphere region that contains sufficient number of electrons which disturb the propagation of radio signal travel from navigational satellite to ground/user receiver. Ionospheric delay in range measurement is related to its Total Electron Content (TEC). Ionospheric delay results in range error and degrades the user position accuracy of navigational satellite systems such as Global Positioning System (GPS) and Indian Regional Navigational Satellite System (IRNSS). Hence a suitable TEC prediction model to correct the range delay in single frequency range measurement is necessary. In dual frequency receiver, ionospheric delay is estimated and eliminated using the two range measurements performed at the same time. This paper describes the TEC prediction methodology using Ordinary Kriging based Surrogate Model (OKSM). OKSM is evaluated using the data received and collected from the IRNSS receiver station installed at ACS College of Engineering (ACSCE), Bengaluru (12.8913 °N, 77.4658 °E), India and other International GNSS Service (IGS) network stations. IRNSS TEC data (January 2018) is calculated by using dual frequency (L5 & S) pseudo range method and TEC is smoothed by normal cubic smoothing spline method. IRNSS Vertical TEC (VTEC) is predicted from 16 January 2018 to 26 January 2018 by using previous six days of estimated VTEC values. Similarly, GPS VTEC for IGS station at IISC, Bengaluru is also predicted for same duration to validate the developed OKSM. In order to evaluate the performance of the developed forecasting model for different geographic locations, solar activity conditions and seasons, the VTEC is predicted and analyzed for different latitude regions such as low-latitude PHON station (6.9599 °N, 158.2101 °E), mid-latitude ALGO station (45.9588 °N, −78.0714 °E) and high-latitude NRIL station (69.3618 °N, 88.3597 °E) during different solar activity conditions (Low-2008, Medium-2011 and High-2013 solar activity) and during different seasons (spring, summer, rainy and winter) in the year 2017. From the analysis of OKSM prediction results, it is observed that, RMSE of predicted TEC varies from 0.79 to 3.6 TECU, MAE is 0.4 to 3 TECU and MAPE is within 40% for ionospheric quiet days. VTEC is also predicted during storm days (26 October 2003 to 31 October 2003). To study the performance of the model, VTEC prediction results of OKSM are compared with prediction results from Standard Persistence Model (SPM) and VTEC derived from International Reference Ionosphere (IRI-2016) model. The RMSE of OKSM is 1.9679 TECU, MAE is 1.245 TECU and MAPE is 9%, whereas for SPM, RMSE is 4.8372 TECU, MAE is 3.7496 TECU and MAPE is 36%. Similarly, for IRI-2016 model, RMSE is 7.9 TECU, MAE is 7.1976 TECU and MAPE is 66%. Therefore, TEC predictions by OKSM are better than SPM and IRI-2016. The results show that the OKSM is useful for applications in ionospheric studies.

Performance Analysis of Acquisition Algorithms for Navic

Indian Regional Navigation Satellite System (IRNSS), is an indigenous navigation system designed and developed by ISRO (Indian Space Research Organization).It is named as NavIC, Navigation with Indian Constellation by Indian Prime Minister. NavIC is designed to have seven satellite constellation that provides reliable position, navigation and timing services over India. The focal modules of NavIC receiver are acquisition, tracking and navigation unit. Among them, acquisition is the data processing unit for detecting satellite signals and their corresponding code phase and carrier frequency. In this paper, various acquisition algorithms like Serial search and Parallel Code Phase search algorithms are analyzed and compared with Cooley-Tukey FFT algorithm and sub-sampled Fast Fourier transform (ssFFT).The results obtained in MATLAB shows that the acquisition computation time for ssFFT based NavIC receiver is faster than parallel FFT acquisition and the Cooley-Tukey FFT IRNSS acquisition algorithm is faster and provides better code phase and carrier frequency values compared to serial search acquisition algorithm.

Estimation of Differential Code Bias of IRNSS Satellites using Global Ionosphere Map

AbstractIRNSS (Indian Regional Navigation Satellite System) is an independent satellite based regional navigation system, developed by India, with an aim to provide accurate positioning and timing services to user in India as well as 1500 km away from its boundary. IRNSS is a constellation of seven satellites, three satellites are orbiting in a GEO (Geostationary orbit) and remaining four satellites are in GSO (Geosynchronous orbit).IRNSS provides navigation services on two frequencies i.e. L5 (1176.45 ± 12 MHz) and S band (2492.028 ± 8.25 MHz). The measurements from dual frequency IRNSS/NavIC (Navigation with Indian Constellation) receiver are affected by instrument bias of satellite and receiver. Differential Code Bias (DCB) is the hardware bias between two GNSS code at same or different frequency. DCB can't be ignored for both precise positioning as well as for precise TEC estimation. Currently there are limited numbers of IRNSS satellites, so it is difficult to build an independent Ionospheric model for the precise estimation of DCB of IRNSS satellites.There are several Ionospheric Associated Analysis centers (IAAC), providing the DCB (Differential Code Bias) of different GNSS satellites (GPS, GLONASS etc.) along with the Global Ionospheric Map (GIM) on routine basis. Knowledge of DCB is currently unavailable for newly developed constellations like IRNSS, due to the limited number of satellites and monitoring stations. In this paper Global Ionospheric Map (GIM) published by IGS (International GNSS services) is used as a reference for the estimation of DCB of IRNSS satellites. More than 60 days' observation data of IRNSS Range integrity and monitoring station (IRIMS) were analysed and DCB of each day was computed with the stability of up‐to ∼1 ns for all IRNSS satellites in constellation.

System engineering aspects of One‐Way CDMA based Range and Integrity Monitoring Stations (ORIMS) for NavIC system

AbstractNavIC(Navigation with Indian Constellation) system formerly IRNSS (Indian Regional Navigation Satellite System), is an ISRO initiative to build an independent regional satellite navigation system based on seven satellite constellation to provide precise position, velocity and time to users over the Indian region. The NavIC System is designed to provide position accuracy 20 meters over Indian geo‐political boundary and a region extending to the about 1500 Kms around India for a dual frequency user.One of the important elements of ground segment which operates 24×7 unmanned is one‐way CDMA (Code Division Multiple Access) ranging station namely IRNSS Range and Integrity Monitoring Stations (RIMS). This paper provides the system engineering aspects and the challenges involved in engineering RIMS for NavIC.First an overview of RIMS technical design is provided. The architecture of one way IRIMS is explained based on functionality. Then the key techniques of designing IRIMS are described. Also basic technical considerations on the other IRIMS equipment's, like atomic clocks, reference receiver and computing infrastructure are provided. The major role of IRIMS inside NavIC System functions is analyzed.Towards establishment of such one way IRIM Stations the system engineering aspects such as, the site selections requirements, site survey requirements namely Radio Frequency (RF) Survey, Multipath survey, elevation profile survey are presented.

Precision of satellite based navigation position solution: A review using NavIC data

Global Navigation Satellite System (GNSS) provides all-weather, precise Position, Velocity and Timing (PVT) solutions from any point on the surface or near to the surface of the earth. Accuracy and global availability of solutions are the major important attributes for popularization of the system. Currently, various global and regional system (GPS, GLONASS, Galileo, Beidou, NavIC and QZSS) are in operation. Most of users of GNSS are concerned about the quality of solution obtained from the receivers including the researchers. In some published literature the precision parameters have been obtained from position solution in UTM coordinate. In this paper an attempt has been made to briefly review such efforts and discuss about the parameters used for such studies for geodetic coordinate (φ, λ, h) system because, most generic and geodetic high cost receivers provide this type of position solution. A new effort is taken up to calculate the precision parameters of GNSS based position solution in geodetic coordinate reviewing the previously reported literature. The formulas are reviewed and implemented using MATLAB to develop and utility to calculate precision parameters of satellite-based position solution. A new regional navigation satellite system IRNSS/NavIC, developed by ISRO, India has been deployed. IRNSS/ NavIC data has been analyzed using the developed utility as a case study to observe the effectiveness of such parameters. This discussion and the utility would be useful for understanding the process of GNSS data analysis for studies related to accuracy and precision.

Analysing impact of major solar flares on ionospheric TEC with RTISM model using IRNSS receiver, at SVNIT, Surat, India

Indian regional navigation satellite system (IRNSS) is a navigation system developed by the Indian Space Research Organisation (ISRO), India. The IRNSS receiver granted by Space Application Centre (SAC), ISRO, Ahmedabad is installed at SVNIT, Surat, India. A solar flare is a natural event that occurs when an unpredicted flash of distended Sun's illumination is observed near its surface. The ionosphere is greatly ionised by solar radiations. Hence it is a current challenge to investigate effects of ionospheric scintillation on IRNSS signals. This study examines impact of major solar flare events like Class ‘C’ solar flare happened on 22 July 2016 and class ‘M’ solar flare occurred on 23 and 24 July 2016, on IRNSS signals with measurement of total electron content (TEC). Real-time ionospheric scintillation monitoring (RTISM) model based on empirical mode decomposition (EMD) and second-order Daubechies (db2) wavelet is used for comparing measured and denoised TEC. The RTISM model is also used for determining automatic threshold using Neyman–Pearson detector, probability of detection and probability of false alarm. It is proven with analysis that EMD is giving more sharp results as compared to db2 wavelet for determining fluctuations in TEC during the solar flare events.

Analysis of signal strength, satellite visibility, position accuracy and ionospheric TEC estimation of IRNSS

The Indian Regional Navigation Satellite System (IRNSS) is an indigenously developed satellite navigation system to meet practical needs. The system, comprising a constellation of seven satellites in GEO orbit, has been fully operational since 2018. It is essential to evaluate the performance of the IRNSS continuously for various applications. As a part of ISRO field trial and data collection program an IRNSS Standard Positioning Service User Receiver (UR) placed at ACS College of Engineering (ACSCE), Bangalore, for independent field trial and data collection. The receiver is operational on a $24\times 7$ basis. A MATLAB Graphical User Interface has been developed to analyze and plot the data variation of signal strength, elevation angle, visibility of satellites, user position, position error, geometric dilution of precision (GDOP) and find the availability of the number of satellites plotted for every second based on the received data. From the results, it is observed that the signal strength (C/No) is good, i.e. above 40 dBHz, visibility of satellites at receiver location is good. The mean position at user location is found to be $X=1349700~\mbox{m}$, $Y = 6070902~\mbox{m}$, $Z = 1413860~\mbox{m}$ and latitude of 12.8914 degree, longitude of 77.465 degree and altitude of 739 m. The mean position from IRNSS is compared with Google map results showing a good match. The geometry distance of receiver location with respect to Earth center is estimated and observed. The RMS of position error for L1, L5 and dual frequency (L5+S) at ACSCE, Bangalore, is 9.7444 m, 6.6873 m and 5.6667 m, respectively. Hence, as expected the dual-frequency (L5+S) receiver gives an accurate position rather than the single-frequency signals. The IRNSS TEC is measured using Ionospheric group delay and the pseudo-range of L5 and S band which is collected from ACSCE receiver. A third order Savitzky-Golay-Filtered technique is used for TEC smoothing. RMSE between IRNSS TEC from pseudo-range and GPS TEC is 0.6482 TECU and the correlation coefficient is 0.9981. RMSE between IRNSS TEC from ionospheric delay of L5/S and GPS TEC is 1.971 TECU and the correlation coefficient is 0.9966. Finally, smoothed TEC values derived from pseudo-range measurements give a good result and can be used to generate daily TEC maps. In order to analyze the performance of IRNSS over the Indian region, we have chosen three other receiver stations located at Osmania University (Hyderabad), University of Burdwan (Bardhaman, West Bengal) and Shri Mata Vaishno Devi University (Katra, Jammu and Kashmir). Based on the results, we conclude that the IRNSS constellation is performing well and providing good signals for accurate user position determination and ionospheric data analysis.

Carrier Phase Measurement in IRNSS using Antenna swapping Method

Indian has been established its regional navigational satellite system i.e., IRNSS (Indian space research navigation satellite system). It is launched successfully with seven satellites. It provide accurate position to user in Indian and up to 1500km around the India. In this paper, calculated the integer ambiguity (N) which is one of the parameter of the carrier phase measurement. Carrier phase measurement is measure the range between the satellite and receiver expressed units of cycle of the carrier frequency.

Single Stage 180nm CMOS Low Noise Amplifier Topologies and Optimization Algorithms for S Band Frequency

Low Noise Amplifier (LNA) plays an important role in radio receivers. It mainly determines the system noise and intermodulation behavior of overall receiver. LNA design is more challenging as it requires high gain, low noise figure, good input and output matching and unconditional stability. Further, designing a Low noise Amplifier requires active device selection, amplifier topology, optimization algorithms for superlative results. Hence this paper presents performance analysis of CMOS LNA based on different topologies and optimization algorithms for 180nm RF CMOS design in S band frequency. Here the best results, various limitations in each topology are reviewed and required specifications are determined in each designing. Further this best topology is used for designing LNA circuit which could be used in Indian Regional Navigation Satellite System (IRNSS) applications in dual band frequency.

Estimation of Doppler Positioning for NavIC System in Static and Dynamic Conditions

The primary objective of any navigation system is to provide accurate user position. Navigation with Indian Constellation (NavIC) is an emerging regional satellite navigation system being developed by ISRO, India. The positional accuracy of the NavIC depends upon various parameters based on the application. Doppler shift is one among those parameters which plays an important role in finding the user position in dynamic conditions. The effect of the Doppler shift is more in high dynamic applications like missiles launching, air navigation due to high relative velocity between receiver and satellite. In this Paper, an efficient algorithm is developed to estimate the Doppler positioning using least squares method in static and various dynamic conditions. For this, the experimental data acquired from Indian Regional Navigation Satellite System (IRNSS)-GPS receiver located at low latitude station (Hyderabad: 17.39˚N, 78.31˚E) is used. A trajectory path has been simulated to estimate the user position and its accuracy measures in low and high dynamic conditions. It is noticed that, Doppler shift vary ±1KHz for geosynchronous satellites in static conditions, whereas it is ±40KHz in high dynamics. It is observed the position error is high in high dynamics as compared with low dynamics because of the higher Doppler shifts.

Contribution analysis of inter-satellite ranging observation to BDS-2 satellite orbit determination based on regional tracking stations

In order to analyse the contribution of inter-satellite ranging observation to the BeiDou regional navigation satellite system (BDS-2) satellite orbit determination under the condition of regional ground tracking stations, first, the methods of using the observation model, the dynamic parameters dilution of precision (DPDOP), and the satellite position dilution of precision (SPDOP) to describe the contribution of inter-satellite ranging observation to orbit determination accuracy are proposed. Then, based on the measured observation data of the regional ground tracking stations located in China, as well as simulated inter-satellite ranging observation data, the contribution of inter-satellite ranging observation to orbit determination accuracy for the three types of satellites used by BDS-2 is analysed. The results show that the inter-satellite ranging observation improves the solution strength of the dynamic parameters by adding redundant observations without adding new parameters to be estimated, which effectively improves the orbit determination accuracy of the along-track component of Geostationary Earth Orbit (GEO) satellite and the cross-track and radial components of Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites. In addition, under the condition of the regional tracking stations, the inter-satellite ranging observation compensates for the disadvantage that the satellite cannot be tracked by the whole arc segment. The accuracy and continuous stability of the orbit determination solution and the geometry structure of satellites that can be observed by stations and other satellites are significant improved, for which the average DPDOP values of GEO, IGSO, and MEO satellites are improved 50.2%, 73.0%, and 72.1%, respectively.

Optics integrated compact cavity for rubidium atomic frequency standards.

A compact magnetron cavity having integrated optics is designed and realized for a rubidium atomic clock that is being developed for the Indian Regional Navigation Satellite System. This cavity comprises a cylindrical dielectric cell with 25 mm diameter and 25 mm height. The cavity is designed to resonate at the rubidium hyperfine ground-state frequency of 6.8346 GHz with TE011-mode. A loop gap resonator structure is employed to obtain the required uniform mode along the quantization-axis in the cavity. The cutoff frequency of the cavity is designed in such a way that the influence of optics on the cavity mode is negligible and it is well within the tuning range of the cavity. The measured results of the realized cavity match up to 90% with the RF simulation results. The overall volume and mass of the realized cavity are about 86 cm3 and 120 g, respectively, making it suitable for portable space based applications.

Preliminary Analysis of BDS-3 Data Based on iGMAS

The Beidou Navigation Satellite Demonstration System and Beidou Regional Satellite Navigation System are accomplished, and the Beidou Global Satellite Navigation System (BDS-3) is under construction. Nineteen networking satellites have been launched by the end of November 2018. To assess the new and old signals of new networking satellites, the data quality is analyzed from the observation noise and pseudo-range multipath two aspects based on the data of iGMAS stations from 18th to 28th May 2018. The accuracies of BDS-3/GPS combined orbit determinations with B1I/B3I and B1C/B2a are compared. The results show that the data quality of the new signal B2a is similar to that of B1I/B3I, and the data quality of B1C is slightly worse than that of B1I/B3I. Comparing the orbit and clock correction accuracies of overlapped arcs (48 hours), the results with B1C/B2a are slightly better than those with B1I/B3I. The averaged 3D position accuracies (3D RMSs) of precise orbit determinations with B1C/B2a and B1I/B3I are around 35 cm. The RMS values of clock corrections are less than 0.5 ns.

Evaluation of the GPS Precise Orbit and Clock Corrections from MADOCA Real-Time Products.

The Japanese Quasi-Zenith Satellite System (QZSS) is a regional navigation satellite system covering the entire Asia-Oceania region. Except for the standard satellite navigation signals, QZSS satellites also broadcast L6E augmentation signals with real time GNSS precise orbit every 30 s and clock messages every 1 s, which is very important and necessary for Real-Time precise point positioning (RTPPP) applications. In this paper, the MADOCA real-time services derived from L6E augmentation signals were evaluated for both accuracy and availability compared with IGS final products. To avoid the datum difference of GPS orbit between MADOCA real-time and IGS final products, the 7-parameters Helmert transformation was firstly used in this paper, and then the orbit was evaluated on radial, along, and cross-track directions. On the clock evaluation, the mean satellites clock errors were taken as reference clock error, and then the standard deviation (STD) was calculated for each satellite. Furthermore, the signal in space range errors (SISRE) were also summarized to evaluate the ranging-measurement accuracy. Seven-day evaluation results show that satellite orbit, clock errors, and the final SISRE errors range as being 1.8–3.9 cm, 0.04–0.15 ns (1.2–4.5 cm), and 5–10 cm, respectively. For the one-year long-term evaluation, daily SISRE errors in 2018 show consistent performance with that of seven days. Furthermore, the open source software RTKLIB was used to evaluate the kinematic PPP performance based on the MADOCA real-time products, and it shows that the daily positioning accuracy of the 20 globally distributed IGS stations can reach 4.9, 4.2, 11.7, and 12.1 cm in the east, north, up, and 3D directions, respectively. Hence, it is concluded that the current MADOCA real-time ephemeris products can provide orbit and clock products with SISRE on centimeters level with high interval, which could meet the demands of the RTPPP solution and serve real-time users who can access the MADOCA real-time products via L6E signal or internet.

Performance Analysis of Acquisition Algorithms for NavIC

Indian Regional Navigation Satellite System (IRNSS), is an indigenous navigation system designed and developed by ISRO (Indian Space Research Organization). It is named as NavIC, Navigation with Indian Constellation by Indian Prime Minister. NavIC is designed to have seven satellite constellation that provides reliable position, navigation and timing services over India. The focal modules of NavIC receiver are acquisition, tracking and navigation unit. Amongthem, acquisition is the data processing unit for detecting satellite signals and their corresponding code phase and carrier frequency. In this paper, various acquisition algorithms like Serial search and Parallel Code Phase search algorithms are analyzed and compared with Cooley-Tukey FFT algorithm and sub-sampled Fast Fourier transform (ssFFT).The results obtained in MATLAB shows that the acquisition computation time for ssFFT based NavIC receiver is faster than parallel FFT acquisition and the Cooley-Tukey FFT IRNSS acquisition algorithm is faster and provides better code phase and carrier frequency values compared to serial search acquisition algorithm.

An Observational Review on influence of Intense Geomagnetic Storm on Positional Accuracy of NavIC/IRNSS System

ABSTRACT The positional accuracy of Navigation with the Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) in the low latitudes of the Indian region during the intense geomagnetic storm of 8 September 2017 being reported first time. The existence of an intense geomagnetic storm is verified with several geomagnetic indices and interplanetary field parameters. The Total Electron Content (TEC) maps from the International GNSS Service (IGS) data and the thermosphere O/N2 ratio maps from the Global Ultra Violet Imager (GUVI) are also used in the study. The one week of data (3–9 September 2017) are collected based on equatorial region (Trivandrum) and Equatorial Ionization Anomaly (EIA) region (e.g. Surat, Bombay, Hyderabad and Gandhinagar), from India, using the Accord NavIC/IRNSS dual-frequency (L5 and S-band) receivers. For the intense storm day, a comparative study is being carried out for TEC, ionospheric delay and positional accuracy for L5 band. The observations perceive the positive impact in the equatorial region while the negative impact for EIA region, with reference to quiet days of the observed week. The average ∼70% and further ∼25% NavIC/IRNSS system positional accuracy is improved by applying ionospheric correction and augmenting NavIC/IRNSS with GPS system respectively. This study is very much important in satellite-based navigation application for Precise Point Positioning (PPP).

Hypothesis Test-based Detection of Wi-Fi Interference on NavIC/IRNSS S-band Signal

The Navigation with Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) is an emerging satellite navigation system that provides an independent navigation system for positioning and timing services in India and up to 1,500 km from its borderline. The dual frequency NavIC system uses the L5 frequency and S-band for navigation. These navigation signals are extremely weak and susceptible to interference when they are received on Earth's surface. Moreover, the performance of these bands may be degraded by other band or out-of-band communication systems, which can become the major threat to the performance of a NavIC receiver. The main focus of this paper is to detect real-time interference of Wi-Fi signals in the S-band of the NavIC receiver. The results are prepared with respect to the Power Spectral Density (PSD), execution of acquisition stage and the detection of Wi-Fi interference with two sample hypothesis testing methods including the Kolmogorov-Smirnov (KS)-test, the t-test and the Variance (var)-test. A performance analysis of the p-value is used to measure the evidence of interference existence for hypothesis testing, decision hypothesis and probability of detection are evaluated for each hypothesis method. The results show the severity of the Wi-Fi signal as a potential source of interference for future NavIC applications.

Single-Epoch, Single-Frequency Multi-GNSS L5 RTK under High-Elevation Masking.

The Japanese Quasi-Zenith Satellite System (QZSS) satellite system has placed in orbit four satellites by October 2017. The Indian Regional Navigation Satellite System (IRNSS) system has launched the new satellite IRNNSS-11 in April 2018, completing seven operational satellites. Together with the GPS block IIF satellites and the Galileo satellites, four different global navigation satellite systems (GNSSs) are providing precise L5 signals on the frequency of 1176.45 MHz. In this contribution, we challenge the strength of the multi-GNSS model by analysing its single-frequency (L5), single-epoch (instantaneous) precise positioning capabilities under high-elevation masking (up to 40 degrees). With more satellites available, multi-GNSS real time kinematic (RTK) positioning is possible using L5-only signals with a high customary elevation mask. This helps to enable positioning in areas with constrained measurement geometry, and could significantly reduce the multipath effects in difficult measurement environments like urban canyons and mountainous areas. In this study, benefiting from the location of the Asia–Australia area, instantaneous multi-GNSS L5 RTK analysis is performed with respect to the ambiguity resolution and positioning performance. Formal results are shown and discussed for baselines located in different grids covering Australia, part of the Pacific Ocean, Indian Ocean and Asia, and empirical analysis is given for two baselines in Perth, Australia. Compared to the stand-alone cases, for baselines in Perth, it is shown that combining L5 signals from GPS/Galileo/QZSS/IRNSS significantly improves both the ambiguity success rates (ASR) and the positioning performance under high elevation mask. While the average single-system ASR is under 50% even with a low elevation mask of 10 degrees, combining all the four systems increases the ASR to above 95% under an elevation cut-off angles of 40 degrees. With an elevation mask of 40 degrees, using satellites from one system does not allow for meaningful positioning solutions of more than 8 h within the test day, while mm-to-cm level ambiguity-fixed standard deviations could be obtained based on the positioning results of almost the entire day when combining all the four systems. In addition to that, simulation was also performed for receivers with larger signal standard deviations, i.e., for low-cost receivers or receivers located in environments with larger multipath.

Field trial of IRNSS receiver

AbstractIRNSS is an independent regional navigation system being developed by Indian Space Research Organization, India. Ionospheric scintillations are very important to satellite‐based radio communication and navigation. Ionospheric variations are responsible for most of the range error which yields in inaccurate position coordinates and degradation in signal power (carrier to noise power ratio).This article represents a comparative analysis of position error and Ionospheric delay among IRNSS (Indian Regional Navigation Satellite System) and GPS (Global Positioning System) considering the ionospheric correction algorithms being used in both satellite constellations. Grid based ionospheric correction, dual frequency delay correction, and coefficient based have been considered for comparison of both IRNSS and GPS navigation system.