456 research outputs found
Design of a Local Segment of Galileo Based on Stratospheric Platforms
No full textThe use of stratospheric aircraft denoted as High Altitude Platforms (HAPs)
Politecnico di
Torino
Fabio Dovis - Paolo Mulassano
SAS Group
The use of stratospheric aircraft denoted as High Altitude Platforms (HAPs)
represents one of the most challenging perspective for future
telecommunication and remote sensing applications. Long Endurance
operation (weeks to months), reduced costs, possibility of maintenance and
drastic shorter distance from Earth with respect to satellites, make HAPs
attractive for a large class of commercial application
A study of multipath effects on Galileo signals
No full textThe characterization of the error budget related to GNSS can be performed over each component that affects the SIS measurement (pseudorange). Politecnico di Torino Fabio Dovis - Paolo Mulassano NAVSAS Group Considering the Galileo case, there are several error sources due to the receiver design; among them, the major one is the deleterious superimposition of the same SIS received at the antenna via multiple path: the multipath. Such an error is the most important contribution if indoor navigation/positioning is considered, and in addition it is also present in differential-GNSS applications where the reference station is located in a different environment with respect to users. This work presents an overview of possible multipath mitigation techniques applied to Galileo SI
On the Impact of Channel Cross-Correlations in High-Sensitivity Receivers for Galileo E1 OS and GPS L1C Signals
No full textOne of the most promising features of the modernized global navigation satellite systems signals is the presence of pilot channels that, being data-transition free, allow for increasing the coherent integration time of the receivers. Generally speaking, the increased integration time allows to better average the thermal noise component, thus improving the postcorrelation SNR of the receiver in the acquisition phase. On the other hand, for a standalone receiver which is not aided or assisted, the acquisition architecture requires that only the pilot channel is processed, at least during the first steps of the procedure. The aim of this paper is to present a detailed investigation on the impact of the code cross-correlation properties in the reception of Galileo E1 Open Service and GPS L1C civil signals. Analytical and simulation results demonstrate that the S-curve of the code synchronization loop can be affected by a bias around the lock point. This effect depends on the code cross-correlation properties and on the receiver setup. Furthermore, in these cases, the sensitivity of the receiver to other error sources might increase, and the paper shows how in presence of an interfering signal the pseudorange bias can be magnified and lead to relevant performance degradatio
GNSS Interference Threats and Countermeasures
No full textReliable positioning and navigation is becoming imperative in more and more applications for public services, consumer products, and safety-critical purposes. Research for finding pervasive and robust positioning methodologies is critical for a growing amount of societal areas while making sure that navigation is trustworthy and the risks and threats of especially satellite navigation are accounted for. This book provides a comprehensive survey of the effect of radio-frequency interference (RFI) on the Global Navigation Satellite Systems (GNSS) as well as of the spoofing threats.
Through case studies and practical implementation/applications, this resource presents engineers and scientists with a better understanding of interference and spoofing threats, ultimately helping them to design and implement robust systems
The Interference Threat
No full textIt is well known that several phenomena may affect the quality of the pseudor- ange estimation that is based on the measurement of the propagation time of a signal from a satellite to the user. Any electromagnetic source interacting with the signals is interfering with the process of estimating the propagation time. This book focuses on artificial sources of RFI generated either intentionally or unintentionally by some communication system. The following chapters address such sources of artificial interference and the receiver-based techniques used to detect and mitigate their effects. Note, however, that other kinds of interference might be a threat to GNSS positioning performance. They are discussed in the following subsections, but are not be specifically addressed in this book since their detection and mitigation follows specific approache
Interference mitigation based on transformed domain techniques
No full textReliable positioning and navigation is becoming imperative in more and more applications for public services, consumer products, and safety-critical purposes. Research for finding pervasive and robust positioning methodologies is critical for a growing amount of societal areas while making sure that navigation is trustworthy and the risks and threats of especially satellite navigation are accounted for. This book provides a comprehensive survey of the effect of radio-frequency interference (RFI) on the Global Navigation Satellite Systems (GNSS) as well as of the spoofing threats. Through case studies and practical implementation/applications, this resource presents engineers and scientists with a better understanding of interference and spoofing threats, ultimately helping them to design and implement robust system
Wavelet based design of digital multichannel communications systems
No full textThe huge penetration of the personal communications systems in the market is constantly presenting new challenges to the research, aimed at satisfying people's needs and requirements for effective communication systems. At present, the cellular telephone network is perhaps the most evident example of communication system that has had a great impact on the lives of ordinary people and, at the same time, is the subject of interest of many researchers both at academic and industrial level. For the future, one of the main challenges in telecommunications will be the provision of ubiquitous broadband tetherless integrated services to mobile users. Such a pretentious goal cannot be achieved without a continuous research facing such problems as service quality, complete mobility support, and affordable complexity that are still open problems. However, present telecommunication problems are not only a matter of implementation or development of new services, exploiting a totally assessed doctrine. In order to respond to the mobility of the users personal communication systems have to deal with the wireless communication channel whereby mobility and non-stationarity of the propagation conditions require a stochastic description of the channel parameters. While this fact can be viewed as strong limitation to the development of a solid theory whose validity can be assesed in practice, on the other hand allows for an investigation and study of novel communication schemes, sometimes encompassing basic aspects of digital communications. This thesis, is the result of a research work that has investigated one of the basic building block of every communication systems, the modulation scheme, and the design of the pulse shape carrying the digital information. We have studied the design of multichannel communication scheme exploiting the mathematical theory of wavelets. Such a theory, developed recently, has had a great impact in many fields of engineering and of other scientific disciplines. In particular, wavelet theory has become very popular in the signal processing area; in fact it is a flexible toolbox for signal analysis allowing effective representation of signals for features extraction purposes. The main features that make wavelet waveforms suitable to be used as shaping pulses for modulation are their substantial compact support both in the time and frequency domains, and the fact that they are ISI-free pulses over frequency flat channels. The study presented in this thesis is focused on application of wavelet theory to design high-efficiency multichannel communication schemes and to the performance evaluation over linear and non-linear channels. We present a general method to design wavelet based multichannel communication schemes that we denoted Wavelet Orthogonal Frequency Division Multiplexing (WOFDM). We show that such schemes, having a largerspectral efficiency for a small number of channels, are a valid alternative to the classical OFDM. Potential advantage of wavelet modulation are shown presenting other applications examined in this thesis: a joint use of WOFDM and Trellis Coded Modulation to shape the power spectrum in order to match a frequency selective channel and minimize distortion, and application to spread spectrum modulation. Particular attention has been devoted to the timing recovery problem in multichannel communication schemes, exploiting the timing information of the different subchannels to improve the error variance in estimation of the sampling instant leading to a reduction of the adjacent channels interferenc
Classical digital signal processing countermeasures to interference in GNSS
No full textReliable positioning and navigation is becoming imperative in more and more applications for public services, consumer products, and safety-critical purposes. Research for finding pervasive and robust positioning methodologies is critical for a growing amount of societal areas while making sure that navigation is trustworthy and the risks and threats of especially satellite navigation are accounted for. This book provides a comprehensive survey of the effect of radio-frequency interference (RFI) on the Global Navigation Satellite Systems (GNSS) as well as of the spoofing threats. Through case studies and practical implementation/applications, this resource presents engineers and scientists with a better understanding of interference and spoofing threats, ultimately helping them to design and implement robust system
A Comparison Of Transformed-Domain Techniques for Pulsed Interference Removal on GNSS Signals
No full textIt is well-known that GNSS receivers for aeronautical applications operating on the E5a/L5 frequency band have to deal with interfered signals due to the fact that this particular portion of the frequency spectrum is shared with other radio-aiding signals. Classical techniques, such as pulse-blanking, may turn out to be not effective in scenarios of multiple interfering sources. For this reason this paper focuses on a different class of techniques operating an invertible transform of the received signal. Such new representations of the signal allow decomposing the interfered received digital signal in a set of basis function providing a representation of the incoming signal in another domain where the interference can be better identified and removed. Description of these methods and their complexity will be presented when they are used to detect and remove pulsed interference. In particular, the Karhunen-Loève Transform (KLT) is introduced and a preliminary assessment of its performance for pulsed interference mitigation is provide
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