Sarang Thombre

Overcoming the Challenges of BeiDou Receiver Implementation

Global Navigation Satellite System (GNSS)-based positioning is experiencing rapid changes. The existing GPS and the GLONASS systems are being modernized to better serve the current challenging applications under harsh signal conditions. These modernizations include increasing the number of transmission frequencies and changes to the signal components. In addition, the Chinese BeiDou Navigation Satellite system (BDS) and the European Galileo are currently under development for global operation. Therefore, in view of these new upcoming systems the research and development of GNSS receivers has been experiencing a new upsurge. In this article, the authors discuss the main functionalities of a GNSS receiver in view of BDS. While describing the main functionalities of a software-defined BeiDou receiver, the authors also highlight the similarities and differences between the signal characteristics of the BeiDou B1 open service signal and the legacy GPS L1 C/A signal, as in general they both exhibit similar characteristics. In addition, the authors implement a novel acquisition technique for long coherent integration in the presence of NH code modulation in BeiDou D1 signal. Furthermore, a simple phase-preserved coherent integration based acquisition scheme is implemented for BeiDou GEO satellite acquisition. Apart from the above BeiDou-specific implementations, a novel Carrier-to-Noise-density ratio estimation technique is also implemented in the software receiver, which does not necessarily require bit synchronization prior to estimation. Finally, the authors present a BeiDou-only position fix with the implemented software-defined BeiDou receiver considering all three satellite constellations from BDS. In addition, a true multi-GNSS position fix with GPS and BDS systems is also presented while comparing their performances for a static stand-alone code phase-based positioning.

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.

Implementation of a Software-Defined BeiDou Receiver

Satellite-based positioning is undergoing a rapid change. Both the GPS and the GLONASS systems are being modernized to serve better the current challenging applications in harsh signal conditions. These modernizations include increasing the number of transmission frequencies and changes to the signal components. In addition, the European Galileo and the Chinese BeiDou systems are currently under development for global operation. Therefore, the research and development of Global Navigation Satellite System receivers in view of these new upcoming systems has been experiencing a new upsurge. In this paper, the authors discuss the main functionalities of a GNSS receiver in view of BeiDou satellite navigation system. While describing the main functionalities of a software defined BeiDou receiver, the authors also highlight the similarities and differences between the signal characteristics of BeiDou B1 open service signal and the legacy GPS L1 C/A signal, as they both exhibit similar characteristics in general. In addition, the authors implement a novel acquisition technique for long coherent integration in the presence of NH code modulation in BeiDou D1 signal. Finally, the authors present a BeiDou-only navigation fix with the implemented software-defined BeiDou receiver.

A Software Multi-GNSS Receiver Implementation for the Indian Regional Navigation Satellite System

ABSTRACT The Indian Regional Navigation Satellite System (IRNSS) is currently under development with four out of the total planned seven satellites deployed in space. The Department of Navigation and Positioning of the Finnish Geospatial Research Institute (FGI) has been an early adopter of this system in Europe through the development of its software-based multi-frequency multi-GNSS receiver, called FGI-GSRx. This paper presents the results of the first comprehensive IRNSS receiver implementation in Finland, if not in Europe, using the FGI-GSRx receiver. Following a brief description of the IRNSS system, the paper presents the receiver architecture, including the acquisition and tracking stages, and position computation. The results show that IRNSS satellites when used in multi-GNSS positioning can be beneficial in augmenting other satellite systems over north and east Europe. These benefits are expected to grow as more IRNSS satellites are deployed in space in the future. Therefore, the impact of these results is interesting to the positioning, navigation, and timing community even outside the intended service area of IRNSS.

Performance evaluation of carrier-to-noise density ratio estimation techniques for BeiDou Bl signal

The Carrier-to-Noise density ratio (C/N0) in a Global Navigation Satellite System (GNSS) receiver is an important parameter to measure the quality of a GNSS signal. The most traditional C/N0 estimation technique is implemented based on the Narrowband and the Wideband Power Ratio (NWPR), which works just perfectly for the legacy GPS LI C/A receiver. With the advent of new modernized GNSS signals from different systems, some basic signal characteristics of these signals have also changed in such a way that they might no longer enjoy the similar C/N0 estimation performance that NWPR-based C/N0 estimation does for GPS LI C/A signal. For example, in case of BeiDou B1I signal, the presence of an extra tier of modulation (i.e., Neumann-Hoffman code) for Dl signal, and the higher data bit rate in D2 signal may deteriorate the performance of NWPR-based C/No estimation technique. In view of this particular issue, two noise-estimation based C/N0 estimation techniques, namely Signal-to-Noise Power Ratio (SNPR) and Signal-to-Noise Variance Ratio (SNVR), are implemented along with the traditional NWPR-based C/N0 technique for four different GNSS signals in L1/E1/B1 bands. The objective of this paper is to evaluate the performance of these three C/N0 estimation techniques via Matlab-based signal simulations and also via hardware signal simulator and a software-defined multi-GNSS receiver. The simulation results show that the SNPR and SNVR-based C/N0 estimation techniques offer much better estimation performance than the traditional NWPR-based technique in weak signal condition and also with the signals which have relatively higher data bit rate (i.e., BeiDou Bl D2 signal and Galileo El signal).

Maritime Safety – Stakeholders in Information Exchange Process

This paper presents the methodology and research results on identification of potential users of the ESABALT system, which is targeted towards improving the situational awareness in the Baltic Sea region. The authors describe the technique of analysing the stakeholders involved in maritime sector processes, especially in maritime transport processes, while also taking into account their different classification criteria. The resulting list of stakeholders is used to identify system users and their classification into user profiles groups. This study will form the basis for the identification of user requirements of the ESABALT system.

ESABALT Improvement of Situational Awareness in the Baltic with the Use of Crowdsourcing

This paper presents the key assumptions and preliminary research on an integrated system called ESABALT, for enhancing maritime safety, which incorporates the latest technological advances in positioning, e-Navigation, Earth observation systems and multi-channel cooperative communications. The most novel part of the ESABALT concept, however, is a focus on user-driven crowdsourcing techniques for information gathering and integration. The system will consist of a situational awareness solution for real-time maritime traffic monitoring via utilizing various positioning technologies; an observation system of the marine environment relevant to transportation and accidents including assessing the sea ice, oil spread, waves, wind etc.; and a methodology for context-aware maritime communication with cooperative, multi-channel capabilities. The paper presents the intelligent, novel, user-driven solution and associated services developed in ESABALT for enhancing the maritime safety in the whole Baltic area.

Performance of a MEMS IMU deeply coupled with a GNSS receiver under jamming

Satellite navigation signals are very weak in power and, therefore, rather easy to jam for various purposes in both military operations and civilian life. This paper studies the jamming mitigation performance of deep GNSS-INS coupling when a low-cost MEMS inertial measurement unit (IMU) is being used. Deep coupling refers to the integration architecture which implements inertial-aided vector GNSS tracking instead of independent (scalar) tracking loops. In this paper the most important equations involved in noncoherent deep coupling are presented and the tracking performance using the MEMS IMU is compared to the performance obtained using the true antenna position instead of inertial navigation computations. Moreover, the convergence of the integration filter is investigated in the case where only four satellites are available. The results show that the MEMS IMU cannot quite bridge a jamming period of 35 seconds but still outperforms standard unassisted scalar tracking. Moreover, it is observed that an adverse satellite geometry significantly slows down the convergence of the accelerometer bias states of the integration filter while some other states reach a steady state normally.

Performance Analysis of a Dual-Frequency Software-Defined BeiDou Receiver with B1 and B2 Signals

The Chinese BeiDou Navigation Satellite System (BDS) is one of the fastest emerging Global Navigation Satellite Systems (GNSS) that offers two civilian navigation signals through its 14 operational satellites as of November 2014. The release of the 2nd version of the BeiDou Interface Control Document (ICD) in December 2013 makes it possible for the researchers worldwide to investigate the performance of the 2nd civilian BeiDou B2 signal along with the legacy BeiDou B1 signal. In this paper, the researchers at the Finnish Geospatial Research Institute (FGI) make an effort to analyze the performance of BeiDou B1 and B2 signals in Finland considering the similarities and differences between the signals that affect the final positioning result. The performance analysis is carried out in a software-defined multi-frequency multi-GNSS research receiver developed at FGI. The data collection and the result analysis are carried out in two steps. In the first step, a hardware multi-frequency multi-GNSS simulator is utilized to verify the performance of the developed software-defined receiver. Afterwards, in the second step, the performance evaluation of BeiDou B1 and B2 signals is carried out with live data sets.

Software Simulators and Multi-Frequency Test Scenarios for GALILEO

Global Navigation Satellite System (GNSS) signal simulators are essential in supporting education, research, and also development and testing of advanced positioning receivers. This chapter provides useful insights into the essential components of software simulators of GNSS signals, a brief background study of state-of-the-art in such simulators and finally, some test scenarios for testing performance parameters of multi-frequency GNSS receivers. Section “Introduction” is a brief introduction to the following sections of the chapter. Section “State-of-the-Art Software-Based GNSS Signal Simulators” is dedicated to literature review of state-of-the-art in GNSS software simulators. Thirty-eight example simulators available in the academic and commercial domain were selected and their characteristics compared based on the following parameters: the number of GNSS satellite constellations and signals modeled, the strategy of error modeling, the programming language used, the input and output data formats, and the modeling of the radio frequency front-end (RF FE) effects. Section “Important Components of GNSS Signal Simulators” is dedicated to describing the essential components of a typical GNSS software simulator. Usually, such simulators are modular in design, where each module is responsible for a specific functionality. The different modules are the signal generation module, error sources module, transmission channel module, receiver RF FE module, and finally, the space (satellite constellation) module. Lastly, sect. “Multi-Frequency, Multi-System Receiver Performance Test Scenarios” describes some important receiver parameters and their example test-cases in order to compare the performance of a multi-frequency multi-system receiver over its single-frequency single-system counterpart. It has been observed that in spite of the proliferation of numerous simulators of GNSS signals, there is no single comprehensive reference textbook that explains their baseline theory. This chapter intends to fill this gap.