Darshna D. Jagiwala

Bio: Darshna D. Jagiwala is an academic researcher from Sardar Vallabhbhai National Institute of Technology, Surat. The author has contributed to research in topics: Navigation system & Global Positioning System. The author has an hindex of 3, co-authored 7 publications receiving 28 citations.

Impact of dilution of precision for position computation in Indian regional navigation satellite system

Abstract: The System of seven satellites, Indian Regional Navigation Satellite System (IRNSS) will provide Special Positioning Service (SPS) and Precision Service (PS) towards the Indian subcontinent. In Positioning Navigation Timing (PNT) application, measurement is affected by some intentional and unintentional sources of error. This Measurement also depends on the volume of tetrahedron created by the geometry of measuring satellites. The Satellites geometry is measured by single dimensionless numbers called GDOP. Lower the GDOP value, the better the satellite Geometry, hence the position measured by the system is more precise. Currently, IRNSS system has six active satellites in an orbit. In this paper performance analysis of IRNSS, GPS and IRNSS+GPS are investigated by computing the GDOP due to all satellites in view. The performance analysis is done using ACCORD IRNSS receiver which is provided by SAC, ISRO, Ahmedabad. The dual frequency IRNSS receiver of SVNIT, SURAT (21.16° Lat., 72.78° Long.) is explored for best GDOP configuration and position determination over the Indian subcontinent.

Impact of Wi-Fi Interference on NavIC Signal

Abstract: The Navigation with Indian Constellation (NavIC) designed by the Indian Space Research Organisation (ISRO) is an autonomous regional satellite navigation system for providing accurate real-time positioning and timing services to India up to 1500 km from its boundary. The NavIC system exploits L5and S-band for its navigation. The performance of these bands may be interfered by other bands or out-of-band communication systems, which can be the main threat to the performance of the NavIC receiver. This article focuses on real-time out-of-band interference of Wi-Fi signals in the S-band of the NavIC receiver. The performance analysis is carried out with respect to power spectral density, histograms, execution of acquisition stage and parameters of hypothesis testing method like P-value, confidence interval to identify the presence of interference on the NavIC receiver. All these results show that the Wi-Fi signal transmission represents a potential source of interference for NavIC applications and causes severe degradation on NavIC satellite signals.

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

Abstract: 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.

Perception and reduction of Wi-Fi interference on NavIC signals

Abstract: The NAVigation with Indian Constellation (NavIC) system contributes navigation solution all time during all weather conditions, anywhere within India and a region extending about 1500 km around India. The dual-band NavIC system uses the L5 and S bands for navigation. The existence of real-time Wi-Fi signal generates out of band radio frequency interference (RFI) to the S-band signal of NavIC. This interference has been perceived at particular frequencies of the S-band signal of NavIC and the reduction algorithm is proposed for this kind of interference which is based on wavelet packet decomposition. The exact spectral location of the RFI is identified and only affected interfered wavelet coefficients are processed to achieve interference reduction. The results have proven a significant amount of reduction of Wi-Fi interference in the S-band signal.

Case study: NavIC Performance Observation on Low Latitude Region

Abstract: The navigation and positioning system is vital in both civil and military applications. It has become an integral part of our day-to-day life. Navigation with Indian Constellation (NavIC) is the latest addition in the area of satellite-based navigation systems. To achieve the required positioning accuracy of any satellite-based navigation system, the performance accuracy of an individual satellite is more important. The effect of artificial or natural error sources on satellite signals depends on their location, traveling path. In this paper, the NavlC L5-band and S-band signals are considered. The digital IF data is used, which is logged from NavIC receiver, and the performance analysis of NavlC signals has been evaluated in terms of Power Spectral Density, acquisition and post-processing parameters like C / No, elevation angle, pseudoranges, ionospheric delay and troposphere delay concerning the location of NavIC receiver at low latitude SVNIT, Surat Station (21 °9'50.04” N, 72° 47’1.26” E). This kind of analysis can be useful for future applications of the NavlC.

The GIVE Ionospheric Delay Correction Approach to Improve Positional Accuracy of NavIC/IRNSS Single-Frequency Receiver

Abstract: The Navigation with Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) is an independent navigation system developed for the Indian subcontinent by the Indian Space Research Organisation (ISRO). The positional accuracy of this system is mainly affected by the ionosphere of the low-latitude equatorial Indian subcontinent, as large ionospheric gradients and intense irregularities are present in it. The objective of this study is to improve the positional accuracy of NavIC/IRNSS systems by applying ionospheric correction using the most suitable single-frequency model. The data to be analysed were collected from the NavIC/IRNSS receiver provided by the Space Applications Centre, ISRO. A comparative analysis between the dual-frequency model and single-frequency model (e.g. GIVE model, coefficient-based model) was performed on the data from the NavIC/IRNSS receiver. Different ionospheric models were applied to compute ionospheric delay (ionodelay) on a quiet day (3 < K P < 5). Our result shows that both the single-frequency Grid Ionosphere Vertical Error (GIVE) model and dual frequency model outperform remarkably compared to the traditional coefficient-based model. The GIVE model was also analysed on FAR categorized satellites for different stormy days of different months. It was observed that during stormy days also, the 3D position computed by applying the GIVE model was nearly the same as the dual-frequency model.

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 geomagne...

Estimation of ionospheric delay of NavIC/IRNSS signals using the Taylor Series Expansion

Abstract: The delay in Navigation with Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) signals due to the ionosphere are decisive because it leads to significant changes in the positional accuracy of the system. In this paper, we try to estimate the ionospheric time delay (ionodelay) precisely using the local Taylor Series Expansion (TSE) algorithm for a single frequency NavIC/IRNSS system. The performance of the local TSE algorithm is examined by considering two cases. In case I, the TSE was validated under the influence of an intense geomagnetic storm (8 September 2017) by considering NavIC/IRNSS data from the Indian equatorial and Equatorial Ionization Anomaly (EIA) regions. In case II, based on the quiet and disturbed days data, the local TSE model was examined at different locations in the local area (<10 km) using two NavIC/IRNSS receivers (i.e. reference and rover). The results of ionodelay and positional accuracy (Three Dimensional Distance Root Mean Square [3DRMS], Circular Error Probability [CEP], and Spherical Error Probability [SEP]) of NavIC/IRNSS for both the cases indicates that the single frequency local TSE algorithm performs the same as the reference dual frequency model, where as the global eight coefficient Klobuchar and the regional Grid Ionospheric Vertical Error (GIVE) model behaves differently. Therefore, the single-frequency TSE model improves the performance of the NavIC/IRNSS receiver in the local area, and the mathematical coefficient computation and additional frequency hardware cost have been reduced, with the acceptance of a maximum 0.8 m of errors.

Impacts of Intense Geomagnetic Storms on NavIC / IRNSS System

Abstract: The Total Electron Content (TEC) of Navigation with the Indian Constellation (NavIC)/ Indian Regional Navigation Satellite System (IRNSS) was examined under the influence of an intense geomagnetic storm occurred on 8 September, 2017, in the low latitudes of the Indian re- gion. One week (3 September, 2017 to 9 September, 2017) data from five stations located in the equatorial region and in the Equatorial Ionization Anomaly (EIA) area in India are collected from Accord NavIC/IRNSS dual-frequency (L5 and S-band) receivers for the investi- gation. The diurnal TEC comparison between IRI-2007 empirical model and NavIC/IRNSS dual frequency model is done. Through a com- parative study, of TEC at the five locations, we clearly observed geomagnetic storms using dual-frequency NavIC/IRNSS receivers, while the diurnal TEC behavior of the IRI-2017 model was the same on all observation days. On the intense stormy day, we observed an increase of about 19 TECU for the area near the equator and decrease of about 20 TECU in the EIA region compared to other observed quiet days. As a result, positive correlation between TEC and storm occurrence were found in the equatorial region, while a negative one in EIA re- gion. In order to support dramatic change in TEC during intense geomagnetic storm, geomagnetic indices and solar wind/IMF parameters maps are added. The results have been further validated using TEC map from IGS data and thermosphere O/N2 ratio map from Global UV Imager (GUVI).