Unambiguous Acquisition and Tracking Technique for General BOC Signals

This article presents a new unambiguous acquisition and tracking technique for general Binary Offset Carrier (BOC) ranging signals, which will be used in modern GPS, European Galileo system and Chinese BeiDou system. The test criterion employed in this technique is based on a synthesized correlation function which completely removes positive side peaks while keeping the sharp main peak. Simulation results indicate that the proposed technique completely removes the ambiguity threat in the acquisition process while maintaining relatively higher acquisition performance for low order BOC signals. The potential false lock points in the tracking phase for any order BOC signals are avoided by using the proposed method. Impacts of thermal noise and multipath on the proposed technique are investigated; the simulation results show that the new method allows the removal of false lock points with slightly degraded tracking performance. In addition, this method is convenient to implement via logic circuits

Modeling and Simulating GNSS Signal Structures and Receivers

In this thesis an end-to-end simulation was implemented encompassing the important effects from the user segments point of view. The modeling and implementation aimed to take all the relevant features into account that have a direct and significant impact on the performance of a GNSS receiver. In particular, emphasis was on the effects that are hard to formulate and treat theoretically, such as non-linearities, stochastic processes and the highly complex boundary conditions generated by the interaction of the signal with the environment. The three most important parts of the model development are the signal model, the signal propagation model and the receiver model. The signal model is an extension of the well-known signal modeling used to describe GPS signals. The present model was extended to include any sort of signal structure The most important part of the signal propagation model is essentially a ray-tracing algorithm together with the application of the Fresnel equations. This is a 3-D exact specular ray-tracing, which was derived and implemented during the work accompanying this thesis. Beside the signal model the receiver model constitutes a major part of this work. Essentially, it is a dynamic modeling of the tracking process (DLL and PLL). As the model is based on continuous calculus it was a challenge to incorporate the effects of the noise processes. However, this was solved by using the Îto calculus to extend the ordinary differential equations to stochastic differential equations. The implementation was verified by comparing the results to known theoretical expressions and an indirect experimental verification was performed in the sense that some of the theoretical formulas have been compared with experimental data.In dieser Artbeit wurde ein end-to-end Simulator entwickelt, der die wichtigsten Effekte aus der Sicht des Empfängernutzers berücksichtigt. Bei der Modellierung und der Implementierung wurde versucht die Faktoren zu berücksichtigen, die einen wesentlichen Einfluss auf die Performance eines GNSS Empfängers haben. Die drei wichtigsten Modellkomponenten sind das Signalmodell, das Signalausbreitungsmodell und das Empfängermodell. Das Signalmodell ist eine Verallgemeinerung des bekannten Signalmodells, das für die Modellierung von GPS C/A-code Signalen verwendet wird. Dieses Modell wurde für beliebige Signalstrukturen erweitert. Der Kern des Signalausbreitungsmodells ist ein Ray-tracing Algorithmus zusammen mit der Anwendung der Fresnel Gleichungen. Dabei handelt es sich um ein exaktes, dreidimensionales Ray-tracing Modell, das während der Arbeit entwickelt und implementiert wurde. Das Empfängermodell stellt ebenfalls einen wichtigen Teil der Arbeit dar. Im Wesentlichen werden die Regelkreise (DLL und PLL) als dynamischer Prozess modelliert. Das Modell basiert auf einem kontinuierlichen Ansatz, was die Einbindung von Rauschprozessen erschwerte. Durch die Interpretation der gewöhnlichen Differentialgleichungen als stochastiche Differentialgleichungen und Verwendung des Îto Kalküls konnten verrauschte Signale berücksichtigt werden. Die Implementierung wurde durch den Vergleich bekannter theoretischer Ergebnisse verifiziert. Da die meisten theoretischen Ausdrücke schon mit Experimenten verglichen worden sind, kann dies als indirekter Vergleich mit Experimenten gesehen werden

Efficient Delay Tracking Methods with Sidelobes Cancellation for BOC-Modulated Signals

In positioning applications, where the line of sight (LOS) is needed with high accuracy, the accurate delay estimation is an important task. The new satellite-based positioning systems, such as Galileo and modernized GPS, will use a new modulation type, that is, the binary offset carrier (BOC) modulation. This type of modulation creates multiple peaks (ambiguities) in the envelope of the correlation function, and thus triggers new challenges in the delay-frequency acquisition and tracking stages. Moreover, the properties of BOC-modulated signals are yet not well studied in the context of fading multipath channels. In this paper, sidelobe cancellation techniques are applied with various tracking structures in order to remove or diminish the side peaks, while keeping a sharp and narrow main lobe, thus allowing a better tracking. Five sidelobe cancellation methods (SCM) are proposed and studied: SCM with interference cancellation (IC), SCM with narrow correlator, SCM with high-resolution correlator (HRC), SCM with differential correlation (DC), and SCM with threshold. Compared to other delay tracking methods, the proposed SCM approaches have the advantage that they can be applied to any sine or cosine BOC-modulated signal. We analyze the performances of various tracking techniques in the presence of fading multipath channels and we compare them with other methods existing in the literature. The SCM approaches bring improvement also in scenarios with closely-spaced paths, which are the most problematic from the accurate positioning point of view.</p

IF-level signal-processing of GPS and Galileo Radionavigation signals using MATLAB/Simulink®: Including Effects of Interference and Multipath

Open-source GNSS simulator models are rare and somewhat difficult to find. Therefore, Laboratory of Electronics and Communications Engineering in the former Tampere University of Technology (and now Tampere University, Hervanta Campus) has took it upon itself to develop, from time to time, a free and open-source simulator model based on MATLAB/Simulink® for signal processing of a carefully selected set of GNSS radionavigation signals, namely, Galileo E1, Galileo E5, GPS L1, and GPS L5. This M.Sc. thesis is the culmination of those years which have been spent intermittently on research and development of that simulator model. The first half of this M.Sc. thesis is a literature review of some topics which are believed to be of relevance to the thesis’s second half which is in turn more closely associated with documenting the simulator model in question. In particular, the literature review part presents the reader with a plethora of GNSS topics ranging from history of GNSS technology to characteristics of existing radionavigation signals and, last but not least, compatibility and interoperability issues among existing GNSS constellations. While referring to the GNSS theory whenever necessary, the second half is, however, mainly focused on describing the inner-workings of the simulator model from the standpoint of software implementations. Finally, the second half, and thereby the thesis, is concluded with a presentation of various statistical results concerning signal acquisition’s probabilities of detection and false-alarm, in addition to signal tracking’s RMSE

Galileo AltBOC receivers - Analysis of receiver architectures, acquisition strategies and multipath mitigation techniques for the E5 AltBOC signal

Master of Science Thesi

Signal design and Theoretical bounds for Time-Of-Arrival estimation in GNSS applications

Positioning accuracy in satellite navigation systems depends on time-delay estimation (TDE) between satellite transmitted codes and local receiver replicas. This thesis is specifically focused on the problem of improving time delay estimation (TDE) accuracy of SS signals, focusing on the fundamental issue of estimation theory and on the properties of the transmitted signal. TDE fundamentals limits are deeply investigated, encompassing the Cram´er Rao Bound and the Ziv-Zakai Bound, and their modified versions to lighten their computation in presence of unknown parameters, in addiction to the time delay. The adoption of the ZZB as benchmark for both acquisition and tracking stage performance is addressed, analyzing innovative or standard signalling waveforms such as Galileo SIS. The main contributions of this thesis are dealt with the analysis of applicability of spread spectrum continuous phase-modulated (SS-CPM) and spread spectrum filtered multitone (SS-FMT) as ranging signals. A special subset of CPM, labeled as “Semi-integer MSK (SiMSK)” obtained by properly setting the modulation parameters, is revealed easily adaptable to the requirements on emissions, intrinsically constant envelope and spectral efficient, while still allowing good tracking performance. Besides, an ad hoc encoding of the SS-SiMSK enables the design of a constant envelope signal bearing two different rate services, without any approximation at the transmitter side. The analysis of the multicarrier (MC) signal revealed the high degree of freedom in its design, proposing the special Filtered Multitone (FMT) modulation as possible candidate for ranging signals. The strictly bandlimited property and the full spectral flexibility possessed by the FMT are exploited in some cases of study to adapt the system to channel conditions or in particular to emulate existing or innovative spectra. For both the SSCPM and SS-FMT modulation schemes investigated, some estimation algorithms are tested and their performance are compared to the correspondent theoretical bound

Semi-Analytic Techniques for Fast MATLAB Simulations

Semi-analytic techniques are a powerful tool for the analysis of complex systems. In the semi-analytic framework, the knowledge of the system under analysis is exploited to reduce the computational load and complexity that full Monte Carlo simulations would require. In this way, the strengths of both analytical and Monte Carlo methods are effectively combined. The main goal of this chapter is to provide a general overview of semi-analytic techniques for the simulation of communications systems. Specific emphasis is given to their implementation in Matlab and two examples from the communications and navigation context are analyzed in detail. More specifically, the impact of RF interference on acquisition and tracking, the two main stages of a Global Navigation Satellite System (GNSS) receiver, are considered. Although semi-analytic techniques have been considered in textbooks on simulations, limited attention has been provided to their analysis and implementation. This chapter mainly focuses on these two aspects with specific emphasis on the potential of the Matlab environment for their implementation.JRC.G.6-Security technology assessmen

Galileo Signal Generation. Simulation Analysis

Projecte realitzat eb col.laboració amb el Department of Computer and Electronic Engineering. University of LimerickThis work presents the navigation signals and their allocation in the radio frequency band used in the new European Global Navigation Satellite System (GNSS): Galileo. All signals are described mathematically and then simulated using Matlab language (in transmission). Results are shown thus proving the theory provided by the European Space Agency document: “Open Service Signal in Space Interface Control Document” (OS SIS ICD). Before introducing the navigation signals, a deep study and analysis on the modulations and multiplexing schemes (Binary Phase Shift Keying(BPSK), Binary Offset Carrier (BOC), Alternate Binary Offset Carrier (AltBOC), Carrier Adaptative Sub-Carrier Modulation (CASM) and Double Binary Offset Carrier (DBOC) is carried out, also giving detailed results and simulations in Matlab proving the theory again. Moreover, the acquirement of both the autocorrelation function (ACF) and the power spectral density (PSD) of all navigation signals (in Matlab) and all modulations (in theory) is emphasised in the study. Ranging codes are also studied in this work, however from a more practical than scientific point of view, showing how they have been implemented and what type of codes they are (memory codes, based register codes, gold codes). Finally, a paper is provided reviewing the innovative aspects of the navigation signals and why these have been selected for this new GNSS

Enhanced Acquisition Techniques for GPS L1C Receivers

A new, open-access Global Positioning System (GPS) signal, known as L1C, is the most recent of several modernized Global Positioning System (GPS) signals. The first launch of a GPS satellite with this signal is expected to occur within a few years. One of the interesting features of modern Global Navigation Satellite System (GNSS) signals, including GPS L1C, is the presence of data and pilot components. The pilot component is a carrier with a deterministic overlay code but no data symbols; whereas, the data component carries the navigation data symbols used in the receiver processing. A unique aspect of GPS L1C is the asymmetrical power split between the two components, 75% of the power is used for the pilot and the remaining power, or 25%, for the data. In addition, the pilot and the data components are transmitted in phase with orthogonal spreading codes. Unassisted acquisition of GNSS spread spectrum signals requires a two-dimensional search for the spreading code delay and Doppler frequency. For modern two-component GNSS signals, conventional GNSS acquisition schemes may be used on either component, correlating the received signal with either the pilot or the data spreading code. One obvious disadvantage of this approach is the wasting of power; hence, new techniques for combining, or joint acquisition of the pilot and the data components, have been proposed. In this dissertation, acquisition of GPS L1C is analyzed and receiver techniques are proposed for improving acquisition sensitivity. Optimal detectors for GPS L1C acquisition in additive white Gaussian noise are derived, based on various scenarios for a GPS receiver. Monte Carlo simulations are used to determine the performance of these optimal detectors, based on detection and false alarm probabilities. After investigating the optimal detectors for GPS L1C acquisition, various sub-optimal detectors that are more efficient to implement are thoroughly investigated and compared. Finally, schemes for joint acquisition of L1C and the legacy GPS C/A code signal are proposed and analyzed