Test bench solutions for advanced GNSS receivers : implementation, automation, and application

Considerable study has been devoted to the implementation of GNSS receivers for diverse applications, and to finding solutions to some of the non-idealities associated with such receivers. However, not much research is devoted to innovations in their performance evaluation, even though this is an integral step in the overall implementation process. This research work attempts to address this issue through three different perspectives: by focusing on innovation in the testing procedures and test-bench implementation, its automation and its application to advanced multi-frequency, multi-constellation GPS and Galileo receivers. Majority of this research was conducted within the GREAT, GRAMMAR, and FUGAT projects funded by EU FP6/FP7 and TEKES respectively, during which the author was responsible for designing test-scenarios and performing validations of the implemented receiver solution. The first part of the research is devoted to the study and design of sources of test signals for an advanced GNSS receiver test-bench. An in-depth background literature study was conducted on software-based GNSS signal simulators to trace their evolution over the past two decades. Keeping their special features and limitations in view, recommendations have been made on the optimum architecture and essential features within such simulators for testing of advanced receivers. This resulted in the implementation of an experimental software-based simulator capable of producing GPS L1 and Galileo E1 signals at intermediate frequency. Another solution investigated was a GNSS Sampled Data Generator (SDG) based on wideband sampling. This included designing the entire radio front-end operating on the bandpass-sampling principle. The low noise amplifier designed as part of this SDG has been implemented on a printed circuit board. Phase noise (PN) from the radio front-end’s local frequency generator (LFG) is a source of error that has hitherto not been included in any GNSS signal simulator. Furthermore, the characterization of the baseband tracking loops in presence of this phase noise has not yet been included in the typical receiver test scenarios. The second part of this research attempts to create mathematical models representing the LFG’s phase noise contribution, first for a free running oscillator and later for a complete phase-locked loop (PLL). The effect of such phase noise was studied on the baseband correlation performance of GPS and Galileo receivers. The results helped to demonstrate a direct relation between the PN and the baseband tracking performance, thus helping to define guidelines for radio front-end PLL circuit design in order to maintain a minimum baseband tracking performance within the GNSS receiver. The final part of this research work focusses on describing the automated test-bench developed at Tampere University of Technology (TUT) for analyzing the overall performance of multi-frequency multi-constellation GNSS receivers. The proposed testbench includes a data capture tool to extract internal process information, and the overall controlling software, called automated performance evaluation tool, that is able to communicate between all modules for hands-free, one-button-click testing of GNSS receivers. Furthermore, these tools have been applied for the single frequency GPS L1 performance testing of the TUTGNSS receiver, with recommendations on how they can be adapted to testing of advanced multi-frequency, multi-constellation receivers

Hybridization of GNSS and On-Board Sensors for Validating the Aurora Ecosystem

This paper presents a hybrid navigation algorithm based on loose coupling of the on-board speedometer and inertial sensors of a land vehicle with a GNSS receiver. An Extended Kalman Filter estimating ten error states is used as the hybridization framework. The algorithm is developed to serve as a baseline for the evaluation of the navigation infrastructure of the Aurora ecosystem which is an Arctic test bed for autonomous vehicles and intelligent transport systems. In the experimental tests we focus on the performance of the navigation algorithm during GNSS outages. First, the tests indicate that the quality of GNSS updates has an immediate effect on how fast the position errors accumulate when GNSS becomes unavailable. Second, using low-cost sensors together with the current navigation infrastructure available at the Aurora test site, GNSS position fixes need to be obtained at intervals no longer than 4 seconds in order to maintain a 95 % horizontal positioning accuracy better than 0.2 meters. The results serve as a basis for recommendations for further development of the Aurora ecosystem, suggesting that further positioning infrastructure could be deployed for guaranteeing a navigation performance adequate for autonomous vehicles

Impact Analysis of Standardized GNSS Receiver Testing against Real-World Interferences Detected at Live Monitoring Sites

GNSS-based applications are susceptible to different threats, including radio frequency interference. Ensuring that the new applications can be validated against the latest threats supports the wider adoption and success of GNSS in higher value markets. Therefore, the availability of standardized GNSS receiver testing procedures is central to developing the next generation of receiver technologies. The EU Horizon2020 research project STRIKE3 (Standardization of GNSS Threat reporting and Receiver testing through International Knowledge Exchange, Experimentation and Exploitation) proposed standardized test procedures to validate different categories of receivers against real-world interferences, detected at different monitoring sites. This paper describes the recorded interference signatures, their use in standardized test procedures, and analyzes the result for two categories of receivers, namely mass-market and professional grade. The result analysis in terms of well-defined receiver key performance indicators showed that performance of both receiver categories was degraded by the selected interference threats, although there was considerable difference in degree and nature of their impact

Robustness, Security and Privacy in Location-Based Services for Future IoT : A Survey

Internet of Things (IoT) connects sensing devices to the Internet for the purpose of exchanging information. Location information is one of the most crucial pieces of information required to achieve intelligent and context-aware IoT systems. Recently, positioning and localization functions have been realized in a large amount of IoT systems. However, security and privacy threats related to positioning in IoT have not been sufficiently addressed so far. In this paper, we survey solutions for improving the robustness, security, and privacy of location-based services in IoT systems. First, we provide an in-depth evaluation of the threats and solutions related to both global navigation satellite system (GNSS) and non-GNSS-based solutions. Second, we describe certain cryptographic solutions for security and privacy of positioning and location-based services in IoT. Finally, we discuss the state-of-the-art of policy regulations regarding security of positioning solutions and legal instruments to location data privacy in detail. This survey paper addresses a broad range of security and privacy aspects in IoT-based positioning and localization from both technical and legal points of view and aims to give insight and recommendations for future IoT systems providing more robust, secure, and privacy-preserving location-based services.Peer reviewe

Test bench solutions for advanced GNSS receivers : implementation, automation, and application

Considerable study has been devoted to the implementation of GNSS receivers for diverse applications, and to finding solutions to some of the non-idealities associated with such receivers. However, not much research is devoted to innovations in their performance evaluation, even though this is an integral step in the overall implementation process. This research work attempts to address this issue through three different perspectives: by focusing on innovation in the testing procedures and test-bench implementation, its automation and its application to advanced multi-frequency, multi-constellation GPS and Galileo receivers. Majority of this research was conducted within the GREAT, GRAMMAR, and FUGAT projects funded by EU FP6/FP7 and TEKES respectively, during which the author was responsible for designing test-scenarios and performing validations of the implemented receiver solution. The first part of the research is devoted to the study and design of sources of test signals for an advanced GNSS receiver test-bench. An in-depth background literature study was conducted on software-based GNSS signal simulators to trace their evolution over the past two decades. Keeping their special features and limitations in view, recommendations have been made on the optimum architecture and essential features within such simulators for testing of advanced receivers. This resulted in the implementation of an experimental software-based simulator capable of producing GPS L1 and Galileo E1 signals at intermediate frequency. Another solution investigated was a GNSS Sampled Data Generator (SDG) based on wideband sampling. This included designing the entire radio front-end operating on the bandpass-sampling principle. The low noise amplifier designed as part of this SDG has been implemented on a printed circuit board. Phase noise (PN) from the radio front-end’s local frequency generator (LFG) is a source of error that has hitherto not been included in any GNSS signal simulator. Furthermore, the characterization of the baseband tracking loops in presence of this phase noise has not yet been included in the typical receiver test scenarios. The second part of this research attempts to create mathematical models representing the LFG’s phase noise contribution, first for a free running oscillator and later for a complete phase-locked loop (PLL). The effect of such phase noise was studied on the baseband correlation performance of GPS and Galileo receivers. The results helped to demonstrate a direct relation between the PN and the baseband tracking performance, thus helping to define guidelines for radio front-end PLL circuit design in order to maintain a minimum baseband tracking performance within the GNSS receiver. The final part of this research work focusses on describing the automated test-bench developed at Tampere University of Technology (TUT) for analyzing the overall performance of multi-frequency multi-constellation GNSS receivers. The proposed testbench includes a data capture tool to extract internal process information, and the overall controlling software, called automated performance evaluation tool, that is able to communicate between all modules for hands-free, one-button-click testing of GNSS receivers. Furthermore, these tools have been applied for the single frequency GPS L1 performance testing of the TUTGNSS receiver, with recommendations on how they can be adapted to testing of advanced multi-frequency, multi-constellation receivers

Bandpass-Sampling based GNSS Sampled Data Generator - A Design Perpective

This paper presents the design methodology and simulation results of a sampled data generator (SDG) designed to operate over the whole range of Global Navigation Satellite System (GNSS) frequencies (1164MHz to 1615.5MHz). An SDG is actually a radio front-end (RF FE) that generates digital samples at intermediate frequency (IF), which can be recorded and used in the future as test input to a baseband processing unit. The proposed SDG is based on the bandpass-sampling principle and works over combined (but overlapping) frequency bands of all three GNSS constellations (American Global Positioning System (GPS), European Galileo system and the Russian GLONASS system). It is observed that there is currently no commercially available multi-system multi-frequency GNSS SDG. This paper hopes to fill this gap. First, the overall architecture of the proposed SDG is described, followed by the detailed design of each block, namely, the bandpass & bandstop filters, and the frequency planning for the bandpass-sampling analog to digital converter (ADC).Peer reviewe

Wideband, high gain, high linearity, low noise amplifier for GNSS frequencies with compensation for low frequency instability

This paper presents the design methodology, simulation results and implementation details of a low noise amplifier (LNA) designed to operate over the whole range of Global Navigation Satellite System (GNSS) frequencies (1164MHz to 1615.5MHz). This LNA works over combined (but overlapping) frequency bands of all three GNSS constellations (GNSS consist of the American Global Positioning System (GPS), European Galileo system and the Russian GLONASS system). Designed to be unconditionally stable with gain of over 18dB and noise figure of 2dB over a considerable bandwidth of about 450MHz, the achieved results conformed quite well to the specifications. Final implementation results include a gain of 18.5dB at the centre frequency with a nominal variation of ±1.3dB over the desired bandwidth. The noise figure obtained is 2.18dB and the amplifier stability range extends from OHz to 9GHz. Very high degree of linearity is achieved with output 1dB compression at +13dBm and output third order intercept at +23dBm. This paper describes results at every stage of design, simulation and implementation along with a solution against typical low frequency instability by a small trade-off in noise figure.Peer reviewe

Combating Single-Frequency Jamming through a Multi-Frequency, Multi-Constellation Software Receiver: A Case Study for Maritime Navigation in the Gulf of Finland

Today, a substantial portion of global trade is carried by sea. Consequently, the reliance on Global Navigation Satellite System (GNSS)-based navigation in the oceans and inland waterways has been rapidly growing. GNSS is vulnerable to various radio frequency interference. The objective of this research is to propose a resilient Multi-Frequency, Multi-Constellation (MFMC) receiver in the context of maritime navigation to identify any GNSS signal jamming incident and switch to a jamming-free signal immediately. With that goal in mind, the authors implemented a jamming event detector that can identify the start, end, and total duration of the detected jamming event on any of the impacted GNSS signal(s). By utilizing a jamming event detector, the proposed resilient MFMC receiver indeed provides a seamless positioning solution in the event of single-frequency jamming on either the lower or upper L-band. In addition, this manuscript also contains positioning performance analysis of GPS-L5-only, Galileo-E5a-only, and Galileo-E5b-only signals and their multiGNSS combinations in a maritime operational environment in the Gulf of Finland. The positioning performance of lower L-band GNSS signals in a maritime environment has not been thoroughly investigated as per the authors’ knowledge

Local Oscillator Phase Noise Effects on Phase Angle Component of GNSS Code Correlation

This paper demonstrates the effect of radio frequency (RF) front-end (FE) free-running local oscillator (FRO) phase noise (PN) on the phase component of the Global Navigation Satellite System (GNSS) code correlation product. It is observed that as FE PN increases, it adversely affects the stability of the phase component of the code correlation. The tracking loops in baseband processing of a GNSS receiver attempt to lock on to the frequency, delay and phase of the correlation product. Until these parameters are varying within acceptable bounds, set by the dynamics handling capability of the tracking loops, the tracking loops are able to successfully track the satellite signal. However, PN increases the variation in phase of the correlation product calculated over consecutive epochs and may also cause loss of tracking lock if these variations go beyond phase locked loop (PLL) pull-in range thresholds. This paper studies the relation between FRO PN and phase component of correlation through numerical analysis, and software simulations by artificially contaminating GNSS signal stream with PN of increasing variance and checking the result on the standard deviation (SD) of the phase component of correlation product. Based on these results, this paper recommends certain maximum limits on the FE PN in order to keep the SD of phase component below the onesigma phase error limits of the PLL used in typical GNSS tracking loops.Peer reviewe