In this paper we analyze the design of a digital PLL for a GNSS software receiver. Even if the to... more In this paper we analyze the design of a digital PLL for a GNSS software receiver. Even if the topic of phase tracking has been widely studied, we found it useful to provide a short walkthrough for the design of a PLL in a real software receiver, avoiding to introduce the common theoretical phase-based model and aiming to the practical implementation of a system that deals with frequencies. Nonetheless, our analysis and design will grow away from the canonical approach, in the way that we will not resort to analog filter theory. The result is a PLL which is more reactive than the ones usually found in literature and that implements a simple method to make its bandwidth adaptive with respect to the noise that affects the signal
This paper deals with the problem of false carrier phase lock when a digital PLL is inserted in t... more This paper deals with the problem of false carrier phase lock when a digital PLL is inserted in the channel chain of a digital GNSS receiver. A bad initialization of such a loop on the basis of the acquisition estimate might lead to an erroneous false lock in the carrier frequency and phase. Clearly this false lock affects in a dramatically way the functioning of the receiver. The solution to this problem might be performed both on the acquisition or tracking stages. In this paper the problem of the false lock as well as a solution to it suitable for a software implementation will be presented
This chapter contains sections titled: Introduction Review of Kalman Filtering and Extended Kalma... more This chapter contains sections titled: Introduction Review of Kalman Filtering and Extended Kalman Filtering for Navigation EKF-Based PVT Computation in a Stand-Alone GNSS Receiver Inertial Navigation Fundamentals IMU Alignment General Architecture for the Loose Integration General Architecture for the Tight Integration General Architecture for the Ultra-Tight Integration Conclusions References Appendix A
This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo ... more This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo signals jointly. A large set of possible solution can be implemented, with the main aim of assessing the performance of the receiver for the considered architectures. For this reason, software receivers, either real-time or non-real-time, are fundamental tools to enable research and new developments in the field of GNSSs. In this paper our intent is to discuss some of the choices one can face when implementing an SDR GNSS receiver, switching from the theory to the practice. We focus our attention on the pseudorange construction and the Position, Velocity and Time (PVT) estimation stage, discussing different algorithms to implement these blocks. Our aim is to offer an insight on the options to implement those stages of the receiving chain, in a practical vision which is difficult to find in the available literature.
Advanced and unexpected applications are recently raising new interest in Global Navigation Satel... more Advanced and unexpected applications are recently raising new interest in Global Navigation Satellite System (GNSS) codeless techniques that can be used, for example, for signal authentication and spoofing detection. Moreover, the presence of a subcarrier in modern GNSS signals introduces new challenges and opportunities. To take advantage of modern signal structures, codeless processing needs to be modified to recover the subcarrier which can subsequently be used for signal quality monitoring. In this paper, codeless tracking is modified for processing Binary Offset Carrier (BOC) modulated signals where a Subcarrier Lock Loop (SLL) is used to remove the subcarrier component. The performance of the suggested architecture is thoroughly analyzed and theoretical results are supported by Monte Carlo simulations. An open-loop, multi-correlator codeless architecture is also proposed to monitor the BOC subcarrier correlation function. The effectiveness of the proposed codeless framework is...
Proceedings of the 2012 IEEE/ION Position, Location and Navigation Symposium, 2012
This paper presents experimental results showing the impact of the proposed LightSquared Long Ter... more This paper presents experimental results showing the impact of the proposed LightSquared Long Term Evolution (LTE) signals on reception of both Global Positioning System (GPS) and Galileo civil signals in the L1/E1 band. A model for determining the impact of the interfering signal on the victim Global Navigation Satellite System (GNSS) receivers is also provided and this model is validated
IEEE Transactions on Aerospace and Electronic Systems, 2000
ABSTRACT Undesired interfering signals are considered to be one of the main threats to the correc... more ABSTRACT Undesired interfering signals are considered to be one of the main threats to the correct behavior of new Global Navigation Satellite System (GNSS) receivers. There is a huge variety of interference that can occur in the real world, such as narrow band, wide band, impulsive, stationary, or nonstationary CWs. Processing techniques based on time-frequency (TF) distributions allow one to detect and mitigate many different types of these undesired signals. A TF mitigation technique is proposed to enable GNSS receivers to reduce the interference affecting the incoming signal. The proposed algorithm uses a synthesis technique based on the orthogonal-like Gabor expansion, in order to obtain an estimate of the interference, that is then subtracted from the input signal. In the presence of a wide class of deterministic interfering signals, the proposed mitigation strategy is effective in terms of acquisition and tracking performance and outperforms other algorithms described in the literature.
This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo ... more This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo signals jointly. A large set of possible solution can be implemented, with the main aim of assessing the performance of the receiver for the considered architectures. For this reason, software receivers, either real-time or non-real-time, are fundamental tools to enable research and new developments in the field of GNSSs. In this paper our intent is to discuss some of the choices one can face when implementing an SDR GNSS receiver, switching from the theory to the practice. We focus our attention on the pseudorange construction and the Position, Velocity and Time (PVT) estimation stage, discussing different algorithms to implement these blocks. Our aim is to offer an insight on the options to implement those stages of the receiving chain, in a practical vision which is difficult to find in the available literature.
In this paper we analyze the design of a digital PLL for a GNSS software receiver. Even if the to... more In this paper we analyze the design of a digital PLL for a GNSS software receiver. Even if the topic of phase tracking has been widely studied, we found it useful to provide a short walkthrough for the design of a PLL in a real software receiver, avoiding to introduce the common theoretical phase-based model and aiming to the practical implementation of a system that deals with frequencies. Nonetheless, our analysis and design will grow away from the canonical approach, in the way that we will not resort to analog filter theory. The result is a PLL which is more reactive than the ones usually found in literature and that implements a simple method to make its bandwidth adaptive with respect to the noise that affects the signal
This paper deals with the problem of false carrier phase lock when a digital PLL is inserted in t... more This paper deals with the problem of false carrier phase lock when a digital PLL is inserted in the channel chain of a digital GNSS receiver. A bad initialization of such a loop on the basis of the acquisition estimate might lead to an erroneous false lock in the carrier frequency and phase. Clearly this false lock affects in a dramatically way the functioning of the receiver. The solution to this problem might be performed both on the acquisition or tracking stages. In this paper the problem of the false lock as well as a solution to it suitable for a software implementation will be presented
This chapter contains sections titled: Introduction Review of Kalman Filtering and Extended Kalma... more This chapter contains sections titled: Introduction Review of Kalman Filtering and Extended Kalman Filtering for Navigation EKF-Based PVT Computation in a Stand-Alone GNSS Receiver Inertial Navigation Fundamentals IMU Alignment General Architecture for the Loose Integration General Architecture for the Tight Integration General Architecture for the Ultra-Tight Integration Conclusions References Appendix A
This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo ... more This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo signals jointly. A large set of possible solution can be implemented, with the main aim of assessing the performance of the receiver for the considered architectures. For this reason, software receivers, either real-time or non-real-time, are fundamental tools to enable research and new developments in the field of GNSSs. In this paper our intent is to discuss some of the choices one can face when implementing an SDR GNSS receiver, switching from the theory to the practice. We focus our attention on the pseudorange construction and the Position, Velocity and Time (PVT) estimation stage, discussing different algorithms to implement these blocks. Our aim is to offer an insight on the options to implement those stages of the receiving chain, in a practical vision which is difficult to find in the available literature.
Advanced and unexpected applications are recently raising new interest in Global Navigation Satel... more Advanced and unexpected applications are recently raising new interest in Global Navigation Satellite System (GNSS) codeless techniques that can be used, for example, for signal authentication and spoofing detection. Moreover, the presence of a subcarrier in modern GNSS signals introduces new challenges and opportunities. To take advantage of modern signal structures, codeless processing needs to be modified to recover the subcarrier which can subsequently be used for signal quality monitoring. In this paper, codeless tracking is modified for processing Binary Offset Carrier (BOC) modulated signals where a Subcarrier Lock Loop (SLL) is used to remove the subcarrier component. The performance of the suggested architecture is thoroughly analyzed and theoretical results are supported by Monte Carlo simulations. An open-loop, multi-correlator codeless architecture is also proposed to monitor the BOC subcarrier correlation function. The effectiveness of the proposed codeless framework is...
Proceedings of the 2012 IEEE/ION Position, Location and Navigation Symposium, 2012
This paper presents experimental results showing the impact of the proposed LightSquared Long Ter... more This paper presents experimental results showing the impact of the proposed LightSquared Long Term Evolution (LTE) signals on reception of both Global Positioning System (GPS) and Galileo civil signals in the L1/E1 band. A model for determining the impact of the interfering signal on the victim Global Navigation Satellite System (GNSS) receivers is also provided and this model is validated
IEEE Transactions on Aerospace and Electronic Systems, 2000
ABSTRACT Undesired interfering signals are considered to be one of the main threats to the correc... more ABSTRACT Undesired interfering signals are considered to be one of the main threats to the correct behavior of new Global Navigation Satellite System (GNSS) receivers. There is a huge variety of interference that can occur in the real world, such as narrow band, wide band, impulsive, stationary, or nonstationary CWs. Processing techniques based on time-frequency (TF) distributions allow one to detect and mitigate many different types of these undesired signals. A TF mitigation technique is proposed to enable GNSS receivers to reduce the interference affecting the incoming signal. The proposed algorithm uses a synthesis technique based on the orthogonal-like Gabor expansion, in order to obtain an estimate of the interference, that is then subtracted from the input signal. In the presence of a wide class of deterministic interfering signals, the proposed mitigation strategy is effective in terms of acquisition and tracking performance and outperforms other algorithms described in the literature.
This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo ... more This paper deals with a Software Defined Radio (SDR) receiver capable to process GPS and Galileo signals jointly. A large set of possible solution can be implemented, with the main aim of assessing the performance of the receiver for the considered architectures. For this reason, software receivers, either real-time or non-real-time, are fundamental tools to enable research and new developments in the field of GNSSs. In this paper our intent is to discuss some of the choices one can face when implementing an SDR GNSS receiver, switching from the theory to the practice. We focus our attention on the pseudorange construction and the Position, Velocity and Time (PVT) estimation stage, discussing different algorithms to implement these blocks. Our aim is to offer an insight on the options to implement those stages of the receiving chain, in a practical vision which is difficult to find in the available literature.
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