On Generalized Signal Waveforms for Satellite Navigation (797942), страница 8
Текст из файла (страница 8)
This thesis proves thatthe generalized signal waveforms can cover all current signals and other optimized signalsthat could potentially be proposed in the future. Chapters 2 and 3 give a general overview oftoday’s satellite navigation, paying special attention to those aspects related to signal andfrequency design. Chapter 4 presents the theoretical framework this thesis relies on.A second objective of this work is to assess the spectral performance of these generalizedsignal waveforms by analyzing the Spectral Separation Coefficient (SSC).
This figure is ofgreat interest in satellite navigation to understand the interaction of any two signals. Buildingon the generic signal formulas defining the spectrum, generalized expressions are derived forthe SSCs. Particular cases of interest are investigated in detail, using on the one hand side theobtained analytical expression and on the other hand real simulations under ideal conditions.Results show a perfect matching between the predicted analytical results and those obtainedfrom numerical computations, under multiple assumptions. Furthermore, the SSC theory isextended to account also for imperfections and non-ideal effects induced by the codes.Finally, the third main objective of this thesis is to provide a full understanding on current andfuture multiplexing techniques.
This work proposes different solutions to integrate any1Introductiongeneralized signal waveform into an unique multiplexed signal to be transmitted by thesatellite. Pros and Cons of the different solutions are discussed and investigated with regardsto the application for future signal waveforms.To accomplish all these objectives, several tasks have been identified:•To provide an actual description of the signal and frequency plan of all theGlobal Navigation Systems that have played or will play an important role in thecoming decades.
The American GPS and the Russian GLONASS are today in aprocess of modernization that will transform both in dual-use systems. In parallel, theEuropean Galileo project will soon start to work and the Chinese Compass is undercurrent development. This thesis presents their main constellation figures togetherwith other relevant signal and frequency characteristics.•To present a general description of all the Regional Satellite Navigation Systemsthat exist or are under design.
In order to provide improved positioningperformance, Japan (QZSS), India (IRNSS) and China (Beidou) are currentlydeveloping their own regional satellite navigation systems. A detailed description oftheir main parameters will be provided together with a discussion on the future andutility of these regional approaches.•To provide an actual and detailed description of all the current and plannedGNSS Augmentation Systems.
As the number of countries with a global navigationsystem increases, also the requirement to give an answer to particular needs in certainregions gains in interest. To cover this demand, the USA (WAAS), Europe (EGNOS),Japan (MSAS), Russia (SDCM), India (GAGAN), Nigeria (NIGCOMSAT), Canada(CWAAS), China (SNAS) and South America (CSTB), have planned or are currentlydeveloping satellite based augmentation systems to enhance the capabilities of theglobal navigation systems, providing in most cases common operations betweendifferent systems. In addition, other means to augment the navigation signals on aterrestrial basis (GRAS, LAAS, Pseudolites) are also shortly discussed in this work.•To present a clear picture of the evolution of the Galileo Signal and FrequencyPlan over the past years, covering all the gaps in the signal design history that havenot been covered sufficiently in the literature.
An important objective in this regard isindeed to present the evolution of the Galileo Signal Baseline in a comprehensiveway, underlining the drivers that have led Galileo to the final plan it presents today.•To provide a complete description of all the services and signal characteristics ofGalileo. This work pursues to present a correct and complete overview of all theaspects of the Galileo’s Signal and Frequency plan, emphasizing on those signals thatdue to their still short life are less known in the literature. Given the importance thatGalileo has played in past years, special attention is dedicated to it.2Introduction•To provide a theoretical framework that describes all current and futurenavigation signals. After a complete overview of the signal structure of currentGNSSes and future modernizations, all the potential modulations of interest forsatellite navigation are presented.
These are shown to belong to a generalized familyof signals, known as Multilevel Coded Symbols (MCS). A theoretical framework willbe set up and used to derive analytical expressions of generic signal waveforms.•To prove that the theoretical framework that describes any generalizednavigation signals covers all current and all new modulations.
This thesis furtherproves that all current signal waveforms are in fact particular cases of the generalizedmodulations that are proposed in this work.•To provide the reader with a list of appropriate tools to evaluate the goodness ofa signal waveform against other potential alternatives. Designing the signal andfrequency plan of any navigation system requires the deep understanding of the effectof any signal characteristic aspect onto the final positioning accuracy.
This workprovides answers to this.•To understand the meaning and importance of the Spectral SeparationCoefficient (SSC), stressing the value of this parameter in the design of theSignal and Frequency plan of any navigation system. The SSCs have been widelyused over the past years to assess compatibility of the candidate signals of all thenavigation systems that exist or are under development. Furthermore, a goodunderstanding of them provides a very rich insight into the global compatibility andinteroperability performance of a modulation.•Based on the theoretical framework that describes analytically any genericsignal, analytical expressions are also derived for the Spectral SeparationCoefficient (SSC) between any two signals.
The analytical SSCs are further crosschecked with results coming from numerical computation showing the validity of thederived expressions.•To assess how non-idealities of the real signal implementations are reflected inthe final performance of a signal. This work will assess the SSCs under ideal andmore realistic conditions, evaluating the potential effects that the drift from the idealcase can cause onto the final performance of a navigation signal.•To investigate the effects of the SSCs on the mutual interference andcompatibility among different navigation systems. Using a generally acceptedinterference model, the influence of the signal waveform on the final compatibilityand interference will be assessed.•One final but ambitious task of this work will be to provide a complete overviewof all the current and potential multiplexing schemes of future and modernizednavigation systems.
Signal Multiplexing has gained in importance over the past yearsas an increasing number of signals and services are planned to be shared in the very3Introductionscarce Radio-Navigation bands that satellite navigation has assigned today. Thisthesis will try to give a comprehensive and complete overview of all the multiplexingschemes that are relevant for satellite navigation, paying special attention to thoseapproaches that GPS and Galileo presently use and will potentially implement in thefuture.The organization of the thesis is determined by these objectives and will be further outlined inchapter 1.3.1.2Contributions of this ThesisThe major achievements of this thesis are enumerated next:•Review of current satellite navigation systems and signal waveforms:o A detailed description of the signal and frequency plans, including the mainconstellation parameters, of all the global, regional and augmentationnavigation systems that exist today or are planned for the coming years.o A detailed overview of how the Galileo Signal and Frequency Plan hasevolved over the past years, providing insight into the technical drivers thathave led to the baseline that Galileo presents today.o A complete overview of all the signal waveforms that have been relevant in thepast decades and of those that could potentially become alternative formodernized Satellite Navigation Systems.o A complete description of the Galileo baseline signals and services as well asof other candidates that were relevant in the past years together with anassessment of their potential positioning performance.•Development of new theory on signal design for satellite navigation:o A mathematical framework capable of describing any generic signal waveformis developed and analytical expressions derived.
This is further used to obtaingeneral expressions for the Spectral Separation Coefficients.o Derivation of analytical expressions and theory of generic Multi-CodedSymbol (MCS) Signals and their particular cases. By using this theoreticalframework it is shown that any signal can be in principle expressed followingthe generalized theory on MCS signals.o Derivation of analytical generalized expressions for the Power SpectralDensities that can describe all signals, modulations and multiplexing schemesthat are used today or could be used some day in the future to enhancenavigation.4Introductiono Analysis of the MBOC modulation and its different implementations by GPSand Galileo as well as possible receiver architectures for GPS and GalileoE1/L1 common receivers.o Derivation of analytical expressions for the Spectral Separation Coefficients(SSC) of generic Multi-Coded Symbol signals with infinite and limitedbandwidth and generalization to more complex waveforms.
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