1,720,974 research outputs found
Comparative Interference Vulnerability Assessment of GPS TMBOC and Galileo CBOC Signals
No full textAim of this paper is to present an interference impact
assessment in the context of Global Navigation Satellite
Systems (GNSS), focusing on the new modulations based
on the Multiplexed Binary Offset Carrier(MBOC)
scheme that will be used for modernized GPS L1C and
Galileo E1 civil signals.
Simulation results are presented and discussed in order to
perform a comparative analysis of GPS L1C and Galileo
E1 civil signals in presence of Continuous Wave(CW)
interference. Performance is discussed versus the main
signal and receiver parameters that could affect the
interference robustness of the signals and the receiver. In
detail, both double and single channel (data and/or pilot)
tracking schemes have been assessed, varying the receiver
bandwidth, integration time, correlator type and spacing.
The obtained results show that tracking both data and
pilot channels (correlating the incoming signal with
coherent local replica, including both the channels),
similar performance can be obtained by a receiver for
GPS L1C and Galileo E1 Open Service (OS) signals. On
the other hand, some differences can be noticed when the
receivers take advantage of only one channel (e.g.
tracking only the pilot channels), due to their different
power levels and modulation formats.
Some final remarks are also drawn in order to provide
also some guidelines to the reader on how to reduce the
interference impact on MBOC signals by means of a
proper receiver setup
A fully digital model for Kalman filters
Full text linkThe Kalman filter is a mathematical method, whose purpose is to process noisy measurements in order to obtain an estimate of some relevant parameters of a system. It represents a valuable tool in the GNSS area, with some of its main applications related to the computation of the user PVT solution and to the integration of GNSS receivers with INS or other sensors. The Kalman filter is based on a state space representation, that describes the analyzed system as a set of differential equations that establishes the connections between the inputs, the outputs and the state variables of the analyzed system. In the continuous time domain there exists a large class of physical processes with a time evolution well described by means of stochastic differential equations. A typical problem is the need for an equivalent system in the discrete time, due to the discrete nature of the data to be processed. In the literature, it is quite common to solve this problem in the continuous time domain and to approximate the solution using a Taylor series approximation, to obtain an approximate discrete time version of the continuous time problem. By the way, other methods exist, based on the possibility to transform a continuous-time system to a discrete-time system by means of transformations from the Laplace complex plane to the z plane. These methods are widely used in the digital signal processing community, for example, to design digital filters from their analog counterparts. The main advantage of this approach is that it is very easily implemented by applying some mechanical rules. Moreover the nature of the approximation introduced by the Laplace-z transformation is a-priori known and clearly readable in the frequency domain. In the following the classical methods based on the Taylor approximation and on the Laplace-z transformations will be analyzed and compare
Codes Cross-Correlation Impact on the Interference Vulnerability of Galileo E1 OS and GPS L1C Signals
No full textThis paper presents an assessment study of the impact of the spreading code properties in the reception of Galileo E1 Open Service (OS) and GPS L1C Multiplexed Binary Offset Carrier (MBOC) signals. The distortion of the discrimination function due to codes cross-correlations properties is analyzed, considering the features of the modulation schemes and investigating also different code families. Simulation results demonstrate that the S-curve of the code synchronization loop can be affected by an asymmetry and a bias in the lock point. Such a distortion can be noticed only in case of receiving a single channel (e.g. the pilot channel), whereas it is not present if the received signal is correlated with a coherent local replica including both data and pilot channels. This effect depends on the code cross-correlation properties and on the receiver setup (reception of data/pilot channels, variable correlators spacing). As a demonstration of its impact on a real single channel receiver, it is also shown that in presence of an interfering signal such a distortion can be magnified and lead to relevant performance degradatio
Trustworthiness GNSS signal validation by a time-frequency approach
No full textIn a short time new demanding applications, as for instance financial and life critical timing and positioning services, will be included in the plethora of uses of new Global Navigation Satellite System (GNSS). They will require the ability to restrict access to some class of protected information by the user position meaning, provided by some GNSS technology. Access control tokens using trusted GNSS receivers will provide the information security core for this kind of applications, including banking, enterprise and secure timestamps. In this paper a Time-Frequency (TF) signal validation algorithm is proposed as valuable tool both to define metrics to quantify the trustworthiness of the navigation signal and to provide countermeasure to the receiver functionalities. This algorithm can work as a subfunction of a signal conditioning stage placed between the Analog-to- Digital Converter and the acquisition block in an innovative secure GNSS receiver. The proposed method is based on a synthesis technique using the so called Orthogonal-Like Gabor Expansion in order to obtain an estimation of the interference to be subtracted to the input signal. Tests have been conducted using Continuous Wave (CW), chirp interference and combination of them added to GNSS signals. Baseline GPS BPSK(1), TMBOC(6,1,4/3,3), BOC(1,1) and Galileo CBOC(6,1,1/11) modulations are simulated for the scope by a software GNSS simulator. The algorithm performance are evaluated at the output of the acquisition stage by means of Receiver Operative Characteristics (ROC) curves, showing encouraging results in terms of mitigation effectivenes
Design of a complete GNSS signal analysis software tool and application to assess the interference robustness for GNSS signals
No full text
An Interference Impact Assessment Model for GNSS Signals
No full textThe significant growth of the number of applications based on position information and navigation technology is one of the reasons that pushed the investigation of methods for evaluating the signal robustness and reliability. Among the several aspects to be investigated when comparing different signals performance, the robustness to multipath effects and to external interference (i.e., radiofrequency signals generated by other transmission systems) have to be accomplished. When dealing with the interference issue, one of the main problems is the large number of unknown parameters needed to model the signal (modulation type, spectral bandwidth, etc). Aim of this paper is the definition of new families of curves, called Interference Error Envelope (IEE), able to assess the impact of the interferer on different GNSS signals. Continuous Wave (CW) and Wide Band (WB) interference signals are considered in order to obtain IEE and Interference Running Average (IRA) curves for different modulation signals like Multiplexed Binary Offset Carrier (MBOC) formats. Their performances in terms of interference robustness will be evaluated and compared with those of the well known modulations (Binary Phase Shift Keying, BPSK, or Binary Offset Carrier, BOC(1,1)
A Method to Assess Robustness of GPS C/A Code in Presence of CW Interferences
Full text linkNavigation/positioning platforms integrated with wireless communication systems are being used in a rapidly growing number of new applications. The mutual benefits they can obtain from each other are intrinsically related to the interoperability level and to a properly designed coexistence.
In this paper a new family of curves, called Interference Error Envelope (IEE), is used to assess the impact of possible interference due to other systems (e.g., communications) transmitting in close bandwidths to Global Navigation Satellite System (GNSS) signals. The focus is on the analysis of the GPS C/A code robustness against Continuous Wave (CW) interference.</jats:p
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