Evolution of the Global Navigation SatelliteSystem (GNSS)

Navigation signals are the basis of satellite navigation systems, which determine the navigation systems' performance (such as tracking accuracy, anti-interference capability etc.), and are determined by some constraints (such as radio frequency resources, construction cost, technology level etc.). The aim of signal design is to select "proper" signals considering these above factors and make tradeoffs between performance and constraints. This paper will summarize the signal structure evolution of present satellite navigation and conclude some principles and issues which will be greatly valuable to our 2nd satellite navigation system. There's four main satellite positioning systems presently, the U.S. Global Positioning System (GPS), the Russian Global Navigation Satellite System (GLONASS), the Europe Galileo satellite navigation system and the Chinese BD-1 satellite positioning system. Among these systems, the signal characteristics of GPS and Galileo are good reference to our 2nd satellite navigation system. The improvement of GPS signals is a main aspect of GPS modernization. The aim of GPS modernization is mainly to modernize its signal structure so as to improve the whole systems' performance. The signal structure of Galileo has been revised for several times, and its present signal is the results of long time signal design. From GPS modernization and Galileo signals status, we can summarize some key specifications of navigation signals and some technologies to support these specifications. Based on this, we'll discuss some problems which should be attentive in our country's 2nd satellite navigation system and give some suggestions. This paper is organized into five sections. The first section will give a brief introduction of present satellite navigation system and their main features. Section two will review the GPS and Galileo signals structure evolution, including GPS modernization, Galileo signals status and the comparison of two systems' signals. In the third section, the relationship between signal parameters and system performance will be analyzed, including RF signal characteristics, modulation type, ranging code (such as code type, length and rate) and navigation data. In section four we will discuss some inspiration and technologies concerning our 2nd satellite navigation system, such as the use of multiple frequency signals (ionospheric delay estimation and carrier ambiguity resolution), pilot tones & dataless channel, binary offset carrier (BOC) modulation, and so on. The last section is conclusion, in which the whole paper will be retrospected and some useful conclusion will be given.

The Global Navigation Satellite Systems (GNSS) applications are growing and more pervasive in the modern society. The presence of multi-constellation GNSS receivers able to use signals coming from different systems like the american Global Positioning System (GPS), the european Galileo, the Chinese Beidou and the russian GLONASS, permits to have more accuracy in position solution. All the receivers provide always more reliable solution but it is important to monitor the possible presence of problems in the position computation. These problems could be caused by the presence of impairments given by unintentional sources like multipath generated by the environment or intentional sources like spoofing attacks. In this thesis we focus on design algorithms at signal processing level used to assist Integrity operations in terms of Fault Detection and Exclusion (FDE). These are standalone algorithms all implemented in a software receiver without using external information. The first step was the creation of a detector for correlation distortion due to the multipath with his limitations. Once the detection is performed a quality index for the signal is computed and a decision about the exclusion of a specific Satellite Vehicle (SV) is taken. The exclusion could be not feasible so an alternative approach could be the inflation of the variance of the error models used in the position computation. The quality signal can be even used for spoofinng applications and a novel mitigation technique is developed and presented. In addition, the mitigation of the multipath can be reached at pseudoranges level by using new method to compute the position solution. The main contributions of this thesis are: the development of a multipath, or more in general, impairments detector at signal processing level; the creation of an index to measure the quality of a signal based on the detector's output; the description of a novel signal processing method for detection and mitigation of spoofing effects, based on the use of linear regression algorithms; An alternative method to compute the Position Velocity and Time (PVT) solution by using different well known algorithms in order to mitigate the effects of the multipath on the position domain.

The Global Navigation Satellite System (GNSS), the US Global Positioning System (GPS) at its core but the Russian GLONASS and other systems also at play, is destined to be the basic infrastructure of the forthcoming information age, producing vast civil applications and markets. With the whole world going to be reliant on the GPS that is still owned and operated by the military of a single nation (as also is GLONASS), concerns are being raised in various circles as to the adequacy of the civil world becoming wholly reliant on those military systems. Awareness is increasing worldwide of navigation satellites’ implications as a foremost 21st century issue that transcends civil and national security boundaries. The European Union has embarked on the development of Galileo as an independent, non-military, GNSS. Various meetings have been held between Japanese and US Governments since 1996 on GPS issues, the most recent being the second annual “Japan-US GPS Plenary Meeting” held in October 2002.This paper addresses such issues with a focus on the Japanese situation, especially those surrounding the Japan-US GPS meetings, in the hope that they may serve the purpose of promoting first, the recognition of these issues by other people, and second, the understanding of the situation peculiar to Japan, the world’s second largest economy and perhaps the largest civil GPS user nation. The special Japanese sensitivity to space and national security issues, a survey of developments of Japan-US GPS meetings, and reports of discussions of related topics in other international forums are all discussed. It is apparent that there is a barrier in Japan between the civil and national security views, which is especially conspicuous in the Japan-US GPS meetings, and that international discussions point to the responsibility of user nations to deny the GNSS service to “hostile users”. All concerned, whether in Japan or elsewhere, should transcend the vertical “turfs” to come to grips with the whole GNSS issue as their own responsibility, to recognize and be prepared for the threat of a 21st century “Navigation War”.KeywordsGlobal Position SystemGlobal Navigation Satellite SystemGlobal Navigation Satellite SystemNational SecurityTechnical InteractionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Indian Regional Navigation Satellite System (IRNSS) is a very important space sensor network for navigation in India. In January 2017, IRNSS-1A which was one of the seven satellites of IRNSS lost the ability to provide position information because the three Rubidium atomic clocks on board IRNSS-1A failed. This event had a bad effect on the positioning accuracy of IRNSS. In this paper, we use STK to give a simulation about IRNSS, compare the positioning accuracy of IRNSS before and after IRNSS-1A failed, and analyze the degradation of IRNSS.

Indian Regional Navigation Satellite System (IRNSS) is an independent, indigenously developed satellite navigation system by India. The ASIC design of the digital baseband receiver is the major requirement of any IRNSS handheld device for navigation. This work focuses on design and implementation of IRNSS signal acquisition in time domain. The major challenge in the time domain approach is the increase in acquisition time. By taking advantage of the straight forward implementation with less resource the serial search acquisition is designed by parallelizing frequency search for all carrier frequency bins considering maximum Doppler shift in the range of +/-10KHz with 500Hz resolution and code phase using serial search for half chip resolution. The numerically controlled oscillators are designed using quarter sine wave look-up table supporting a minimum resolution of 0.015Hz. The decision for the presence of the signal is done on the run without storing the intermediate results thereby reducing the memory requirement. The code is implemented in RTL (Register Transfer Level) using VHDL without using any third party IP core. The prototype is validated by implementing in Xilinx XC7Z045FFG900-2 FPGA. The acquisition time obtained is 1.023s for one satellite and the resources utilized is less (as given in Table-1).

Global navigation satellite systems (GNSS) historically been known as one of the newest technologies since the 1970s.GNSS originally developed for military purposes in the USA (GPS -Global Position System).There are several satellite systems in the world.Satellites, International Research Base Stations, regional/national and local base stations form a permanent geodetic frame.Research on the size and shape of the Earth-planet, climate, sea, urban planning.In geodesy, a network of global positioning base stations makes it possible to assess the movements of continents, land plates at international level.GNSS is an important technology in navigation, logistics, economics, land surveying and other "geo" sectors.GNSS equipment/receivers and their manufacturers are applying new designs and electronics.Initially, GNSS instruments were used with single frequency signal reception, later expanding the number of GNSS signal channels to two frequencies.Such technological improvements nowadays improve the certainty, reliability and accuracythe overall quality of GNSS measurements.The GNSS base station enables the surveyors to determine coordinates with an accuracy of two centimeters in real time (RTK) and with an accuracy of five millimeters using the accumulated post-processing data.Various types of factors hamper GNSS measurements.The GNSS signal (radio wave) travels in airspace, in urban environments and is a physical parameter.Any obstacletree, building walls, and atmospheric effectmakes GNSS measurements less accurate.The GNSS signal must be strong and free from attenuation and suppression effects.This study develops GNSS models that show the comparison, certainty and reliability of GNSS measurements using different types of GNSS techniques.Evaluation of Latvian Global Positioning Reference Station Network -LatPos system measurements against a corresponding RTK solution method using Latvian Global Positioning Network geodetic point (G2 class).

This article deals with the development of a legal regime for liability of regional navigation satellite systems, especially in context of the Republic of India. In the near future, various significant sectors and applications in India will depend on the Indian Regional Navigational Satellite System (IRNSS). However, navigation satellite systems and applications relying on information provided by the navigation satellites are not immune from irregularities. In case of any damage caused on account of such malfunction, there is a need for developing a legal regime governing civil liability for satellite systems. The development for a liability regime for satellite based services captured the attention of International Organizations and various interested parties twenty years ago, and intensive consultations have taken place at Unidroit and various international institutions, however the subject has eluded any consensus among stakeholders till date. In light of recent developments in international policy on satellite navigation, an international convention is the appropriate but unlikely answer. Development of regional agreements or national legislations may pave way for a future convention. Hence, a study on liability for satellite navigation systems at national level holds more relevance today. An Indian perspective on legal liability for navigation satellite systems is significant because it is one of the few countries to have developed self-sufficient navigation satellite systems and while there have been plenty of legal studies on American or European satellite systems, legal literature on the Indian system is scarce. This article aims at analyzing concepts relating to a normative liability law for IRNSS.

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.

This paper presents an investigation into the performance of real-time Global Navigation Satellite Systems (GNSS) Precise Point Positioning (PPP) in New Zealand. The motivation of the research is to evaluate the feasibility of using PPP technique and a satellite based augmentation system such as the Japanese Quasi-Zenith Satellite System (QZSS) to deliver a real-time precise positioning solution in support of a nation-wide high accuracy GNSS positioning coverage in New Zealand. Two IGS real-time correction streams are evaluated alongside with the PPP correction messages transmitted by the QZSS satellite known as MDC1. MDC1 corrections stream is generated by Japan Aerospace Exploration Agency (JAXA) using the Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis (MADOCA) software and are currently transmitted in test mode by the QZSS satellite. The IGS real-time streams are the CLK9B real-time corrections stream generated by the French Centre National D’études Spatiales (CNES) using the PPP-Wizard software, and the CLK81 real-time corrections stream produced by GMV using their MagicGNSS software. GNSS data is collected from six New Zealand CORS stations operated by Land Information New Zealand (LINZ) over a one-week period in 2015. GPS and GLONASS measurements are processed in a real-time PPP mode using the satellite orbit and clock corrections from the real-time streams. The results show that positioning accuracies of 6 cm in horizontal component and 15 cm in vertical component can be achieved in real-time PPP. The real-time GPS+GLONASS PPP solution required 30 minutes to converge to within 10 cm horizontal positioning accuracy.

A Global Navigation Satellite System (GNSS) concept based on an open system architecture (OSA) has been developed by the authors. As described in this paper, this GNSS OSA concept utilizes the Global Positioning System (GPS) signal-in-space interface as the foundation for its interoperability standards. So long as each GNSS component adheres to these interoperability standards, synergy is enabled at the individual satellite level and the overall whole becomes much more than the simple sum of its components. The biggest beneficiaries of this GNSS OSA concept are those military and civil/commercial users of satellite navigation services who already have equipment compatible with the GPS signal-in-space interface (i.e., dual use). With the recent decisions in Europe to proceed with the civil Galileo system, on-going international development of space-based augmentation systems, and several industry announcements of plans to build commercial regional positioning systems, the dual-use GNSS OSA concept described in this paper provides a technical roadmap for the future global evolution of satellite navigation.

Purpose The purpose of this paper is to present the problem of implementation of the differential global navigation satellite system (DGNSS) differential technique for aircraft accuracy positioning. The paper particularly focuses on identification and an analysis of the accuracy of aircraft positioning for the DGNSS measuring technique. Design/methodology/approach The investigation uses the DGNSS method of positioning, which is based on using the model of single code differences for global navigation satellite system (GNSS) observations. In the research experiment, the authors used single-frequency code observations in the global positioning system (GPS)/global navigation satellite system (GLONASS) system from the on-board receiver Topcon HiperPro and the reference station REF1 (reference station for the airport military EPDE in Deblin in south-eastern Poland). The geodetic Topcon HiperPro receiver was installed in Cessna 172 plane in the aviation test. The paper presents the new methodology in the DGNSS solution in air navigation. The aircraft position was estimated using a “weighted mean” scheme for differential global positioning system and differential global navigation satellite system solution, respectively. The final resultant position of aircraft was compared with precise real-time kinematic – on the fly solution. Findings In the investigations it was specified that the average accuracy of positioning the aircraft Cessna 172 in the geocentric coordinates XYZ equals approximately: +0.03 ÷ +0.33 m along the x-axis, −0.02 ÷ +0.14 m along the y-axis and approximately +0.02 ÷ −0.15 m along the z-axis. Moreover, the root mean square errors determining the measure of the accuracy of positioning of the Cessna 172 for the DGNSS differential technique in the geocentric coordinates XYZ, are below 1.2 m. Research limitations/implications In research, the data from GNSS onboard receiver and also GNSS reference receiver are needed. In addition, the pseudo-range corrections from the base stations were applied in the observation model of the DGNSS solution. Practical implications The presented research method can be used in a ground based augmentation system (GBAS) augmentation system, whereas the GBAS system is still not applied in Polish aviation. Social implications The paper is destined for people who work in the area of aviation and air transport. Originality/value The study presents the DGNSS differential technique as a precise method for recovery of aircraft position in civil aviation and this method can be also used in the positioning of aircraft based on GPS and GLONASS code observations.

An ever increasing number of low Earth orbiting (LEO) satellites is, or will be, equipped with retro-reflectors for Satellite Laser Ranging (SLR) and on-board receivers to collect observations from Global Navigation Satellite Systems (GNSS) such as the Global Positioning Sys- tem (GPS) and the Russian GLONASS and the European Galileo systems in the future. At the Astronomical Insti- tute of the University of Bern (AIUB) LEO precise or- bit determination (POD) using either GPS or SLR data is performed for a wide range of applications for satellites at different altitudes. For this purpose the classical numeri- cal integration techniques, as also used for dynamic orbit determination of satellites at high altitudes, are extended by pseudo-stochastic orbit modeling techniques to effi- ciently cope with potential force model deficiencies for satellites at low altitudes. Accuracies of better than 2 cm may be achieved by pseudo-stochastic orbit modeling for satellites at very low altitudes such as for the GPS-based POD of the Gravity field and steady-state Ocean Circula- tion Explorer (GOCE).

With the capability to record Global Navigation Satellite Systems (GNSS) data at high-rate, at sampling rates typical for seismological applications, experiments are needed to quantify the response of GNSS to shaking from earthquakes. There have been a few studies that examine the response of GNSS to strong shaking. Recently, Ebinuma and Kato (2012) used a global positioning system (GPS) simulator to electronically test several GNSS receivers and obtain the receiver characteristics at three frequencies: 1, 2, and 5 Hz. The results showed that the amplitude of 5-Hz displacements recorded by the GPS was, depending on the receiver model, between 30 and 125 percent more than the displacement input to the simulator. At low frequencies, the GPS displacement was nearly equal to the input displacement. In addition, Ebinuma and Kato (2012) examined how each receiver model amplified an earthquake displacement record in the 2–8 Hz band. The study discussed here builds on the tests by Ebinuma and Kato (2012), but rather than using electronic simulation, the tests are setup outdoors and closer to actual field installations of GNSS equipment. The authors used a one-dimensional shake table capable of 400 mm of displacement and high acceleration; the shake table also is constrained by a precision linear slider to have very low tilt that would affect inertial sensors. In addition, the stage position can be accurately monitored independent of the GNSS hardware and, importantly, provides a reference to compare with the estimated displacements from the GNSS data. The tests spanned a greater frequency range from 0.2 to 20 Hz and used equipment from three different manufacturers covering five different combinations of receivers and antennas. In addition, the authors have been able to simulate the frequency response of the GNSS equipment using a simple, causal filter. The quality of the filter was tested using additional test data where a step function in displacement was applied to the shake table. The observed displacements from the GNSS data show an overshoot in displacement at the time of the step or transition of the stage. That overshoot was accurately predicted using the filter design derived from the sinusoidal displacement tests.

Indian regional navigation satellite system (IRNSS) is our own navigation system designed to provide various navigational and timing services in Indian region. The present paper discusses ionospheric scintillation effects on IRNSS signals in Surat, (21.16°N, 72.68°E; Geomagnetic 12.90°N, 147.35°E) India, a low latitude station. Ionospheric scintillations are one of the major sources of errors in satellite communication which may results in loss of lock of with particular satellite causing discontinuity of satellite services. Ionospheric Scintillation is experienced by satellite signals when propagating through various layers of atmosphere in terms of random fluctuations in amplitude and phase of signals, and also causes ionospheric delay. The present analysis is done on 3rd October 2015 data for calculation of Ionospheric scintillation measuring parameters like total electron content (TEC) and Vertical TEC using IRNSS data. During this time only four satellites were launched from PRN 1 to 4 by Indian space research organization (ISRO). The comparative behavioral analysis of TEC variation is done using Gaussian distribution function (GDF) and Nakagami m (NGK) model distribution. The carrier to noise (C/N) ratio and elevation angle variations for satellite PRN numbers from 1 through 4 is also carried out. It is seen from comparative analysis that total electron content variations in this geographical location are more following the Nakagami distribution as compared with GDF. The results can be utilized further for developing model for analyzing variations in TEC in this region.

This paper addresses topics concerning the development of future Unmanned Aerial Vehicles (UAV) so that they can operate safely within the community of the Federal Aviation Administration (FAA) and the International Civil Aviation Organization (ICAO). Studies by the Defense Science Board; the Office of Science and Technology; Government Accountability Office; and the Congressional Research Service: Library of Congress; have all emphasized that soon there will be a significant number of UAVs operating sideby- side with manned civil aircraft in the FAA’s National Airspace System (NAS). It is anticipated that future UAVs will start to perform many of the dull, dirty, and dangerous civilian missions. In 2006, about 600 UAVs are expected to be manufactured in the US alone. Therefore, there is an urgent need for developers of UAVs to understand safety certification for operations in the NAS, and that safety certification starts with the safety requirements; safety design; safe development process; safety verification; and safe operating procedures in the planned operational environment. This paper presents and discusses the experiences and lessons gained by the authors on the development of end-toend aviation safety; from the safety requirements to their final safety certification in the planned operational environment. The authors’ previous and ongoing works include the Global Navigation Satellite Systems (GNSS) systems such as the GPS; WAAS; LAAS; MSAS; GPS III; and different operational environments at different airports such as Incheon International Airport. The FAA started with the two traditional safety certifications processes: airborne system certification and ground system certification; governed mostly by Federal Aviation Regulations (FAR) and FAA’s Acquisition Management System (AMS), respectively. However, when FAA started to implement GNSS, the lines between airborne and ground systems became blurred, and as a result many current Communications, Navigation, Surveillance, and Air Traffic Management (CNS/ATM) systems have to follow both processes. We will also discuss the current Safety Management Systems being developed by both FAA and ICAO as an integrated, systematic, and harmonized approach and process to sort out the differing safety requirements from FAA, SAE-ARP, MIL-STD, RTCA, ASTM, ICAO, etc. to provide the eventual safe operations within the NAS. The discussion will then focus on the real world of institutional, operational, and technical issues for safety certification worldwide. Despite the numerous standards and guidance documents, many past safety analyses and studies were guided by best practices that had been used successfully in the past to streamline the process of providing all the required documentations and verifications. One such area is in the use of the “Integrity Panel of Experts” that had been used successful in the implementation of safety for the FAA’s Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS) programs. In many areas of the world, safety certification from a technical point of view is only the first step to achieving safety certification to fly in their national and sovereign airspace. Finally, we will show the first steps that UAV manufactures need to consider if they want their UAVs to be approved to fly safely in different national civilian airspace.