Davide Margaria

Method for Assessing the Interference Impact on GNSS Receivers

The definition of new families of curves named interference error envelope (IEE) and interference running average (IRA) is presented. Such tools are able to assess the impact of RF interference on different GNSS receivers, taking into account the features of the in-band interference source. In fact the actual impact on the final performance is strictly related to the specific receiver architectures. Continuous wave (CW) and wide band (WB) interference signals are considered in order to assess by means of IEE and IRA the robustness of new modulations based on the multiplexed binary offset carrier (MBOC) scheme for several receiver configurations, by varying the discriminator spacing, type, and the front-end filter bandwidth. Interference robustness is evaluated and compared with those of the well-known binary phase shift keying (BPSK) and binary offset carrier BOC(1,1) modulations. Simulation and theoretical results are validated by means of laboratory tests, proving the reliability of IEE curves for interference impact assessment.

An assisted high-sensitivity acquisition technique for GPS indoor positioning

The extremely low signal-to-noise ratio experienced indoors impairs the acquisition stage of common GPS receivers, since reliable correlation peaks are hardly detected.

Galileo AltBOC signal multiresolution acquisition strategy

Herein, some critical aspects related to the acquisition of the future Galileo signals are discussed. In particular, the Alternative Binary Offset Carrier (AItBOC) modulation that will be used by the Galileo satellites to broadcast navigation signals on the E5 band is considered, addressing acquisition issues only partially analyzed in previous works. The implementation of an acquisition section for the AltBOC signals is not straightforward, since several different receiver architectures can be used and remarkable differences are required with respect to the conventional signal processing used in GPS receivers. The main problems that must be handled (risk of false lock, resolution of the search space, and computational burden) are outlined in the following. An innovative technique, called multiresolution acquisition and tailored to the AltBOC signals, is then proposed as an effective solution to previous problems. As demonstrated by means of simulations, this novel strategy can be successfully used in coherent dual-band AltBOC receiver architectures with a feasible implementation complexity and it leads to remarkable advantages in terms of acquisition time.

A novel local integrity concept for GNSS receivers in urban vehicular contexts

This paper proposes a novel concept of “local integrity” suitable to Global Navigation Satellite System (GNSS) receivers in urban vehicular scenarios. The idea is to take into account not only the system, but also the environment nearby the receiver in its nominal conditions, exploiting the potentialities offered by a Vehicular Ad-hoc Network (VANET) infrastructure. In detail, the potential availability of multiple observations of GNSS signals, taken by different vehicles participating to a VANET, can be shared and combined in order to implement a collaborative spatial/temporal characterization and prediction of the local degradations of the GNSS signals. These concepts are intended to pave the way for the reconsideration/redefinition of the classic GNSS integrity concept, in order to overcome the major problems and limitations to its applicability in urban vehicular scenarios. The analytical development of the proposed methodology and the suitable network architecture for its implementation, as well as some validation results, are presented and discussed in the paper.

Assessment on low complexity C/No estimators based on M-PSK signal model for GNSS receivers

In a GNSS receiver the measure of the carrier to noise power density ratio (CNo) is not only a measure of the strength of the received signal, but is also used to determine the lock condition of the carrier and tracking loops and to control the channel scheduling. This paper investigates the possibility of implementing various low complexity C/No estimators, properly adapted from the digital communications world in a real GPS/Galileo receiver. After a theoretical analysis, the paper presents the performance evaluation carried out on different C/No estimation techniques, through both simulated and real GPS signals. We used a real-time GPS/Galileo software receiver, that guaranteed a high level of flexibility and helped to analyze and compare the C/No estimators under test.

A Method to Assess Robustness of GPS C/A Code in Presence of CW Interferences

Navigation/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.

A new peer-to-peer aided acquisition approach exploiting C/N 0 aiding

The aim of this paper is to present an acquisition strategy for Global Navigation Satellite System (GNSS) signals exploiting aiding information provided by GNSS receivers in a Peer-to-Peer (P2P) positioning system. This work sheds light on the benefits of sharing information regarding the received satellite signal power: the Carrier-to-Noise density ratio (C/N0) estimated by aiding peers relatively close to each other, is used to optimize signal acquisition capability in terms of detection performance as well as Mean Acquisition Time (MAT). The proposed approach has been validated and assessed using real data collected with an experimental setup in light indoor conditions and by means of simulations. The performance obtained has also been compared with an Assisted-GNSS (A-GNSS) like acquisition strategy, showing the benefits of the availability of C/N0 aiding information in terms of MAT.

N-FUELS and SOPRANO: Educational tools for simulation, analysis and processing of satellite navigation signals

In recent years, research activities in the field of Satellite Navigation have boosted worldwide. At the same time, it has become evident that few educational opportunities in the field were available for students and there was a need to develop dedicated tools for hands-on sessions. To partially answer this need, the NavSAS Group has developed N-FUELS and SOPRANO. N-FUELS, a MATLAB®-based signal simulator, allows students to understand the physical layer of the Global Navigation Satellite Systems (GNSS) signals and to learn how to manipulate them via software. SOPRANO, a collection of ANSI C language routines, implements the whole chain of GNSS signal elaboration in post-processing and enables testing and validation of new GNSS signal processing algorithms and architectures. Both tools are used in post-graduate courses at Politecnico di Torino with a high degree of internationalization, which opens interesting points of discussion concerning the introduction of novel educational tools able to meet the demand and the learning styles of students with different educational backgrounds and cultures.

On the interference mitigation based on ADC parameters tuning

The function of the front-end of a global navigation satellite system (GNSS) receiver can be roughly described as the provision of received signal samples at intermediate frequency (IF) to the base band section. Due to the low power of the received signal, several phenomena might threat the correct operation of the front-end, and consequently degrade the performance of the acquisition and tracking stages. Among them, the interference from external electromagnetic sources is one of the most dangerous, due to the variety of candidates each with different features, that might affect the GNSS signals. This paper aims at presenting an analysis of the different blocks of the receiver chain in terms of performance degradation, due to the presence of wide-band interference. In particular the focus will be on the assessment of the impact of the tuning of the parameters of the analog to digital converter (ADC) on the receiver robustness to interfering sources.

Assessing GPS Robustness in Presence of Communication Signals

A constantly increasing number of new applications are based on wireless communication system integrated with navigation/positioning platforms. The mutual benefits they can obtain from each others 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 generated by other systems (e.g. communications) on Global Navigation Satellite System (GNSS) signals. The focus is on the analysis of the GPS C/A code robustness.