Navigation With Indian Constellation Research Articles

Correlation between rate of TEC index and positioning error during solar flares and geomagnetic storms using navigation with Indian constellation receiver measurements

Abstract The real-time position accuracy of the Global Navigation Satellite System (GNSS)/Navigation with Indian Constellation (NavIC) receiver is limited by the dynamic behavior of the ionosphere, particularly in adverse conditions like solar flares and geomagnetic storms. The NavIC satellites broadcast dual coherent radio beacon signals on L5 (1,164.5 MHz) and S (2,472.5 MHz) bands for providing position, velocity, and timing services in all weather conditions. The Total Electron Content (TEC) and Rate of TEC Index (ROTI) are the potential indicators for characterizing the ionosphere and its irregularities. In this research work, the TEC and ROTI are computed from the code and carrier phase observations of the NavIC receiver located at Kurnool low latitude station (15.79° N, 78.07° E) with geomagnetic coordinates (7.30° N, 151.65° E). This paper presents a statistical study of TEC, ROTI, and the correlation between ROTI and NavIC positioning error during highly intense solar flares (X9.3 and X2.2) and geomagnetic storm conditions. Compared to quiet days mean TEC, the enhancement is 3 TECU due to X9.3 flares, and the maximum peak of TEC on storm day (September 8, 2017) is 80.92 TECU. Moreover, the correlation coefficient between ROTI and position error is 0.76 on a quiet day (September 4, 2017), 0.54 on an intense solar flares day (September 6, 2017), and 0.24 on a storm day (September 8, 2017), this indicates positional accuracy degradation on a geomagnetic storm day. The outcome of this research work would be helpful for investigating characteristics of the northern low latitude ionospheric irregularities and, in turn, useful for developing suitable ionospheric nowcasting/prediction models for GNSS applications.

Implementation and testing of single point positioning on IRNSS/NavIC receiver data

SummaryIndia has developed its own regional navigation satellite system called the Indian Regional Navigation Satellite System (IRNSS), also known as Navigation with Indian Constellation (NavIC). IRNSS/NavIC provides standard positioning and timing services for civilians and restricted services for authorized users. In this paper, single point positioning is implemented on the NavIC receiver data. Estimation techniques of the least squares method and extended Kalman filter are implemented after applying broadcast‐based clock corrections, orbit computation, relative time correction, and ionosphere delay correction for single and dual frequency. A data extraction and storage module is developed to store computed parameters at every intermediate stage in separate files. This is followed by an error plotter module to plot the extracted parameters for each satellite and to separately analyze their performance and the obtained errors. The estimated receiver position is visualized on Google Earth. The absolute error in both estimation techniques ranges between 5 and 15 m throughout the period.

Simulation of range code tracking loop for multipath mitigation in NavIC receiver

Abstract The Operational Navigation with Indian Constellation (NavIC) comprises seven satellites in the orbit, including three in geostationary orbit (GEO) and four in geosynchronous orbit (GSO). NavIC provides both Standard Positioning Service and Restricted Service, using L5 (1176.45 MHz) and S1 (2492.028 MHz) frequencies, with coverage extending 1500 km around the mainland of India. In an urban canyon, multipath interference severely reduces the precision and reliability of NavIC positioning. Many current multipath mitigation techniques often exhibit high computational requirements or reliance on external assistance. In this paper, a ranging code tracking loop is proposed that can sustain either a late or early branch in contrast to the Narrow-Spacing (NS) correlation technique for mitigating multipath for NavIC receiver. The design of proposed code tracking loop is based on steepest descent algorithm. The findings demonstrate that, in terms of calculation time and code multipath mitigation, the suggested technique performs better than both Multipath Estimated Delay Locked Loop (MEDL) and NS correlation. The proposed method produces less than 0.016 chips for the tracking error Standard Deviation (STD). In addition, the recommended method takes 24 % less computation time.

Effect of satellite availability and time delay of corrections on position accuracy of differential NavIC

Abstract The position accuracy of standalone Navigation with Indian Constellation (NavIC) may not be met for certain applications like civil aviation. To improve the position accuracy of the user receiver, the technique used is Differential NavIC, which makes use of Differential corrections. The position accuracy of the user receiver also depends on the satellite availability (i.e. number of satellites available at a certain time instant to estimate the user position) and delay in transmission of differential corrections. In this article, the analysis of differential NavIC using different numbers of visible satellites (satellite availability) and different time delays for transmission of corrections is carried out. For this analysis, three cases are considered, Case I is when all (six) NavIC satellites are visible, Case II is when five satellites (3 Geosynchronous Orbit (GSO) and 2 Geostationary Earth Orbit (GEO)) are visible, and Case III is when five satellites (3 GEO and 2 GSO) are visible. The comparative analysis for these three cases is carried out with respect to the position accuracy parameters and Geometric Dilution of Precision. It is observed that, with the satellite availability in case I and case III, the user receiver accuracy is approximately the same. In case III, the accuracy of the user receiver (3.08 m) is similar to the accuracy (3.09 m) in case I. For time delay in transmission of corrections, different time delays (0, 5, 10, 20, …, 300 s) are considered to observe the effect on the positional accuracy of the user receiver. Due to the increase in this time delay, there is a significant degradation in the user receiver position accuracy of differential NavIC.

The IRNSS/NavIC designing characteristics and development in antenna application: An overview

<p class="abstract">Today is a generation of the satellite navigation system and every country needs its own positioning and secured services. GPS invention has given birth to a new era in technology. India in terms of population is highly dense and should have its own navigation system. High-level research is still going on for Navigation with Indian Constellation (NavIC) the Indian Regional Navigation Satellite System (IRNSS) to be developed for the frequency band L-band (1176.45MHz) and S-band (2492.08 MHz). In this paper, we summarize the attributes characterizing the NavIC antenna which includes patch size, polarization, Fractal attributes, etc. Similarly, the paper gives technical inputs to develop a compact and efficient NavIC antenna system for future L-band and S-band.</p>

A computationally efficient Kalman filter-based RAIM algorithm for aircraft navigation with GPS and NavIC

Integrity monitoring with a Kalman filter (KF) has recently attracted significant attention. In this paper, a computationally efficient architecture of a KF-based receiver autonomous integrity monitoring (RAIM) algorithm is discussed for aviation applications to ensure reliable operations of Global Navigation Satellite Systems (GNSS). It is built on the Schmidt KF navigation processor to model time-correlated measurement errors. Reasons for important design choices of the algorithm are clarified. Different strategies are adopted to efficiently include the contributions of past KF measurements in fault detection as well as protection level (PL) calculations. Module-wise most significant numerical complexity is also analyzed in detail. The algorithm performance is studied with simulated Global Positioning System (GPS) and Navigation with Indian Constellation (NavIC) signals for a number of scenarios. They comprise different configurations related to the number of satellites, geometry, total duration, and aircraft dynamics. Fault detection performance of presented KF RAIM is shown to be superior to another innovation-based test with a moving time window. It is demonstrated that KF RAIM running on a single-core virtual machine can complete processing within a small fraction of each time interval. The performance is also analyzed by restricting CPU usage. The processing time of GPS-NavIC KF RAIM at every interval is shown to be consistently less than that of standalone GPS in all scenarios. Therefore, dual constellations not only result in lower PLs, but also require shorter execution times. An explanation for faster execution times with dual GNSS is provided using the numerical complexity of different modules.

Integrity monitoring of NavIC by parsing broadcast ephemeris

Abstract Global navigation satellite systems (GNSS) are used to provide position estimation to the users. These navigation systems must meet the required navigation parameters (RNP) parameters. Among them integrity being the important parameter, defined as a navigation system’s honesty of the information provided to the user by satellites. The extremity of error due to clocks, ephemeris etc., broadcasted in navigation message of NavIC will result in inaccurate information provided by the satellites that tamper the Navigation with Indian constellation (NavIC) system integrity. The information provided by the satellites may be faulty due to various error sources and cannot be used for applications which require very high accuracy. Integrity of the information provided by satellites plays a vital role and the system needs to be notified accordingly. The traditional methods receiver autonomous integrity monitoring (RAIM) algorithms require both navigation and observation data for implementation and involves several computations, hence in this paper an efficient approach considering only navigation message is proposed to monitor the integrity of NavIC. The NavIC Navigation data of 28 days data corresponding to 4 months is collected from IGS website. The integrity check is performed considering the satellite‘s User Range Accuracy Upper Bound (URA UB), fit interval and health parameters from navigation message. It is observed from the results that there are specific instances of integrity failure of NavIC system. However, it is also noticed that 99.5 % of times the integrity provided by NavIC is within specified limits that guarantee the NavIC utility for critical applications.

Comparative analysis of regression algorithms for the prediction of NavIC differential corrections

Abstract Indian Regional Navigation Satellite System (IRNSS) or Navigation with Indian Constellation (NavIC) provides positioning, navigation and timing information services to various users in Indian region. Standalone NavIC may not meet the position accuracies for certain application such as civil aviation. Differential NavIC is used for improving the position accuracy of rover receiver, which make use of differential corrections (transmitted from reference station). However, if the satellite signals are temporarily lost due to abruptly changing atmosphere, satellite health issues or if the satellite signals are attenuated due to city infrastructures in urban areas, tree canopies, the accuracy of NavIC will be degraded. This article compares regression tree and bagging tree based differential corrections prediction algorithm with the actual differential corrections, by considering the NavIC satellite signal strength (C/No) and elevation angle (El), to improve the NavIC positioning accuracy. The improvement in the position accuracy is obtained by utilizing predicted differential corrections. The position accuracy of rover using actual differential corrections (2DRMS – 3.09 m), regression tree predicted differential corrections (2DRMS – 5.96 m) and bagged tree predicted differential corrections (2DRMS – 3.06 m) are compared. Here, the rover accuracy using actual differential corrections and bagged tree predicted differential corrections are approximately equal. So, the position accuracy using bagged tree predicted differential corrections are accurate when compared to regression tree predicted differential corrections.

Improving the Position Accuracy of Rover Receiver using Differential Positioning in Indian Regional Navigation Satellite System

Navigation with Indian Constellation (NavIC) is the Indian Regional Navigation Satellite System (IRNSS) developed by Indian Space Research Organization (ISRO) to provide the position and navigation services for Indian region. NavIC or IRNSS is individual satellite constellation which has seven satellites covering the Indian subcontinent. Accuracy of NavIC standalone is insufficient in certain applications such as civil aviation. To improve the position accuracy performance of NavIC system, differential positioning technique is utilized. In this paper, differential positioning is carried out, considering two IGS (IRNSS-GPS-SBAS) receivers (one as reference station and the other as rover), which are capable of receiving IRNSS signals from 7 satellites, GPS signals from 12 satellites, SBAS signals from 2 satellites. Here, NavIC constellation alone is considered for the analysis. The differential positioning is carried out using the pseudorange measurements on L5 (1176.45 MHz), S1 (2492.028 MHz) and dual (L5 and S1 both) and accuracies are compared in terms of the statistical parameters Circular Error Probability (CEP), Distance Root Mean Square (DRMS), 2DRMS (twice the DRMS). The improvement in the horizontal accuracy (2DRMS) of the rover using pseudorange measurements on L5 is observed to be 78.81%, on S1 it is 69.14 % and using dual frequency (L5 and S1 both) it is 80.73% when compared to NavIC standalone.

Time-differenced double difference method for measurement of Navigation with Indian Constellation (NavIC) receiver differential phase bias

The pseudo-range (PR) and carrier phase (CP) observations of Global Navigation Satellite System (GNSS)/Navigation with Indian Constellation (NavIC) receivers are influenced due to various errors like ionosphere delay, troposphere delay, receiver and satellite clock error, multipath, integer ambiguity, receiver hardware noise etc. However, the real-time positioning and navigation applications are in quest of high-quality carrier phase measurements with zero bias. The GNSS/NavIC receiver hardware noise is one of the critical error sources that degrade the quality of carrier phase measurements. And it can be measured by computing the differential phase bias or carrier phase bias employing the double-difference method. This research article proposes a novel approach called Time Differenced Double Difference Carrier Phase (TDDDCP) for estimating differential phase bias or carrier phase bias of NavIC receiver. Moreover, the proposed TDDDCP technique has the advantage over the Double Difference Carrier Phase (DDCP) because it requires data from only one satellite with two zero base length receivers for which the differential phase bias is to be measured. The experimental results show that the differential phase bias value differs for different satellites, ranging from −0.3904 m to 0.3168 m. The bias-free carrier phase observations based on position coordinates (X, Y, Z) found improved precision of standard deviation of 0.4176 m, 0.645 m, and 0.328 m, respectively.

Evaluation of Seasonal Variability of First-Order Ionospheric Delay Correction at L5 and S1 Frequencies Using Dual-Frequency NavIC System

For the precise positioning applications it is important to determine and eliminate the positioning error introduced by various sources such as the ionosphere. To develop a standalone precise navigation system, India has launched the seven satellite constellations for NavIC (Navigation with Indian Constellation) system which can provide precision positioning over India and surrounded landmass. Since the ionospheric delay depends on the frequency of the satellite signal and NavIC systems work at different frequencies L5 and S1 than Global Positioning System (GPS) at L1 and L2, it is not possible to use the GPS data-driven study for NavIC based location calculations directly. Thus there is a need for a specialized ionospheric study for NavIC systems. In addition, the ionospheric delay is directly proportional to Slant Total Electron Content (STEC) which is dependent upon diurnal and seasonal solar activity. To achieve accurate positioning facilities, there is also a need for evaluation for seasonal variability of ionospheric delay correction for NavIC receivers. This paper deals with the STEC estimation; it's smoothing, and removal of instrumental biases from STEC. The determined true STEC has been used to determine first-order ionospheric delay correction at L5 and S1 frequencies. The delay correction at S1 has been found less (2–7 m) as compared to L5 (10–30 m). Furthermore, the seasonal variability of ionospheric delay has been analyzed using about 19 months of data (from June 2017 to December 2018) and found that the ionospheric delay follows unique seasonal characteristics which can be utilized for delay modeling. It has been also observed that the geostationary satellites of the NavIC system are more appropriate than geosynchronous satellites for ionospheric related studies.

Mathematical Model Development for Navigation with Indian Constellation (NavIC) L-Band Geo Synchronous Satellite's Direct Signal and Multipath Signals

NavIC L-band satellite signal that travels from the satellite to the receiver undergoes mainly shadowing and multipath effects. In this research paper, NavIC satellites were observing and analyzing signal efficiency for both the direct signal and multipath signal over the Dehradun area. Two open space data series (direct signal and multipath signal) for Dehradun were obtained in this analysis by the satellite receiver. The methodology includes evaluation, testing, and analysis of data in both cases. Based on collected data, a general mathematical model has been developed, describing the signal intensity in the open space context. The both NavIC Mathematical model was validated with the experimental data. The average R2 and RMSE values developed for the direct signal mathematical model were 0.89 and 1.08% respectively which show a good prediction of NavIC C/N0 value with the developed model. For the multipath mathematical model, four cases have been evaluated. Comparing the graphical view of all four cases for C/N0 multipath signal concerning raw NavIC C/N0 multipath signal has been done to select the best mathematical model.

IRNSS Performance Evaluation of SPS Services on Military Aircraft

The essence of this paper is to study and characterise the performance of Indian Regional Navigation Satellite System (IRNSS), also known as NavIC (Navigation with Indian Constellation), in actual dynamic environment by conducting field trials on military aircraft. The dynamic accuracy of IRNSS receiver in terms of position, velocity and altitude has not yet been tested on any aircraft system i.e. commercial or military applications. These field trials and performance evaluation will help in on-field assessment of IRNSS receiver performance with availability of five, six and seven IRNSS satellites. During conduct of trials, IRNSS receiver and IRNSS antenna were placed inside the aircraft. Results analysis of 18 hours flying data depicts position availability of 99.872% with five satellites and 100% position availability with six and seven satellites.

Double difference method with zero and short base length carrier phase measurements for Navigation with Indian Constellation satellites L5 (1176.45 MHz) signal quality analysis

SummaryThe carrier phase (CP) measurements should be unambiguous to achieve the enhanced accuracy of Global Navigation Satellite System (GNSS) services. However, all the real‐time CP measurements are manipulated by different errors, namely, satellite and receiver clock error, ionosphere delay, troposphere delay, integer ambiguity, etc. Even after removing or minimizing all these errors, the CP measurements are influenced by multipath error and receiver hardware residual or bias. In this research article, a double difference (DD) method is proposed to estimate residual or bias in CP observations of Navigation with Indian Constellation (NavIC). The proposed method abolishes all the common errors and provides bias. However, the CP measurement with a bit of bias value can be considered a high‐quality signal. Here, we investigate the quality of NavIC satellites L5 (1176.45 MHz) signal with real‐time measurements obtained through zero base length (ZBL) and short base length (SBL) experiments conducted at Kurnool (15.79°N, 78.07°E), India. The results show that the CP measurement bias of the L5 signal is within the range ±0.338 and ±1.688 m, respectively, for stationary and moving receivers. The bias was enhanced to 3.71 m for the SBL measurements. The results also demonstrate that the bias is low when carrier to noise (C/No) is high, and its range is nearly the same for all the days. This research would be helpful to estimate the bias that improves accuracy of precise point positioning (PPP) applications.

Development of Soil Moisture Inversion Model for Bare Soil Using Navigation With Indian Constellation (NavIC)

This letter aims to develop an inversion model to estimate soil moisture using Navigation with Indian Constellation (NavIC) L-band signal. Several research works suggest that microwave signal property gets affected after reflecting from the soil surface. The nature of the reflected microwave signal depends on the signal’s penetration depth, which is the factor of water content present in the soil surface. NavIC multipath signal can be used for the estimation of soil moisture using this property. The carrier to noise ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(C/N_{\mathrm {o}})$ </tex-math></inline-formula> of NavIC signal is used for this purpose. The model proposed in the letter is based on the relationship of estimated multipath phase value with the volumetric moisture content present in the soil surface. The output of the developed model is highly encouraging. A linear relation relationship with a high correlation coefficient value of 0.902 and root mean square error (RMSE) of 4.03% is obtained between ground truth soil moisture and retrieved soil moisture from developed algorithm.

Applicability of NeQuick G ionospheric model for single-frequency GNSS users over India

&lt;abstract&gt; &lt;p&gt;The major source of error in the positioning of GNSS is from the region of Ionosphere. The single-frequency GNSS receiver cannot eliminate the ionospheric error due to dispersive medium and frequency-dependent. The low-cost GNSS receivers are highly dependent on single-frequency approaches of Ionosphere region popularly known as Klobuchar, NeQuick G, and BDS2 methods to estimate the data of position, velocity and time. The regional satellite navigation system of India, known as Navigation with Indian Constellation (NavIC) adopted ionospheric models based on single-frequency namely, Klobuchar and grid-based correction models. The Klobuchar modelos accuracy is less for predicting ionospheric delays in low latitude regions like India under Equatorial Ionization Anomaly (EIA) conditions. In this paper, the NeQuick G modelos applicability for NavIC users over the Indian region is investigated. NeQuick G modelos performance is validated with dense GPS TEC network data of 26 stations spread across India and IRI-2016 model, during 2014, 2015 and 2016. The predicted TEC results indicate that EIA structures are well captured by NeQuick G and IRI-2016 models. The results indicate that both NeQuick G and IRI-2016 models well predict season asymmetry and decrease of TEC intensity due to descending phase solar cycle activity. It is found that NeQuick G is one of the contenders of single frequency ionospheric models for GNSS/NavIC users in India.&lt;/p&gt; &lt;/abstract&gt;

Carrier-Aided Dual-Frequency Vectorized Tracking Architecture for NavIC Signals

A new carrier-aided dual-frequency vectorized tracking (CA-DFVT) architecture for the Navigation with Indian Constellation (NavIC) is presented. CA-DFVT tracks both NavIC L5 (1176.45 MHz) and S-band (2492.028 MHz) signals concurrently. It uses the precise carrier phase measurements from the S-band signal and the unambiguous code phase measurements from the L5 signal to form a new measurement model for the extended Kalman filter (EKF) to estimate the position, velocity, and time (PVT) solutions. The new measurement model takes advantage of the benefits of the higher frequency S-band signal, i.e., less ionospheric delay and carrier phase noise, as well as the L5 signal’s inherent noise mitigation capabilities. Compared to the single-frequency approach, the dual-frequency approach in CA-DFVT eliminates the ionospheric effect and minimizes other errors, resulting in better navigation solutions. The proposed CA-DFVT enhances the reliability and robustness of NavIC signal tracking and position estimation in interference and high dynamics environments. We used static and dynamic field tests to validate the performance and robustness of the proposed CA-DFVT receiver architecture. In comparison to single-frequency (L5/S-band) vector tracking, the CA-DFVT receiver demonstrated consistent signal tracking and position estimation with higher position accuracy. In the static case, the mean horizontal position accuracy of CA-DFVT improves by approximately 2–4 and 9–14 m compared to L5-only VT and S-only VT, respectively, while, in the dynamic case, it improves by approximately 2–5 and 25–42 m, respectively.

Investigation of Doppler Collision Effects in Kinematic Conditions and its Mitigation for NavIC System

NavIC (Navigation with Indian Constellation) constellation consists of four geosynchronous and three geostationary satellites and it is developed by ISRO, India. It provides position, velocity and timing services. Doppler Collision (DC) is a phenomenon where tracking errors are introduced in the measurements due to cross-correlation between the satellites. If relative doppler between satellites is less than the code loop bandwidth, then DC occurs. In this paper, to analyze DC impact on NavIC, the Doppler shift of each GEO satellite is calculated, the most effected GEO satellite pair is identified. In high dynamic applications like missile launches the effect of DC is very significant. In order to investigate DC in high dynamic conditions a simulation of trajectory path of the receiver is considered. For the precise position estimation, the contribution of DC error will be high, so it needs to be minimized. An efficient algorithm is developed to mitigate the DC using narrow correlator design of the receiver. Using the proposed algorithm, the DC duration for 1C-1G satellite pair has been reduced from 50min 21sec to 2sec in static conditions. Whereas in dynamic conditions from 4h20min 28sec to 5sec with DLL bandwidth of 4Hz and 0.1 chip spacing of receiver design.

IRNSS/NavIC: Indigenous Indian Satellite Navigation Programme

India has a vibrant space programme, and over years has successfully operationalized communication and remote sensing satellites for the benefit of the country. In order to achieve self-reliance in satellite-based navigation service over Indian region, Indian Space Research Organization (ISRO) has initiated the NavIC (Navigation with Indian Constellation) Programme. NavIC is developed to give PNT (Position, Navigation and Time) services for users over Indian region and its neighbourhood with positional accuracy of 20 m and 10 Nano seconds time accuracy. It provides navigation services to Indian landmass and also it extends its service to 1500 km beyond the geopolitical boundary. This paper provides the overview about the IRNSS and its salient features.

An efficient interference mitigation approach for NavIC receivers using improved variational mode decomposition and wavelet packet decomposition

AbstractReliable positioning, timing, and navigation services have become vitally important in safety and security applications. Hence, the need for Global Navigation Satellite Systems (GNSS) is growing continually. However, Continuous Wave Interference (CWI) was found to be one of the major potential threats of GNSS systems which degrades the receiver's performance. So, in this paper, a new approach using Improved Variational Mode Decomposition and Wavelet Packet Decomposition (IVMD‐WPD) has been proposed to mitigate CWI in NAVigation with Indian Constellation (NavIC) receivers. Although VMD is considered as an excellent signal analysis tool in decomposing non‐stationary and complex signals, the accuracy of the decomposition results depends upon the parameter setting. To address this, firstly, Normalized Kurtosis Energy Ratio (nKER) evaluation index is constructed. Then, the principle of nKER maximum is implemented to find the optimal parameters of VMD. Using the optimized parameters, the received signal is decomposed by IVMD into sub‐signals. Secondly, the mutual information index is introduced to extract the information dominant modes. The extracted modes are then processed by wavelet packet filter and finally, the desired signal is reconstructed. The proposed IVMD‐WPD method not only reduces the jamming efficiently but also overcomes the limitations of VMD. Moreover, by integrating IVMD with wavelet packet filter, the remaining effects of jamming and noise present in desired modes can be filtered thereby enhancing the performance. Simulation results reveal that the proposed method performs better in comparison with the conventional techniques in case of a single tone, multi‐tone, and chirp jamming environments.