Impact of non-idealities on GNSS meta-signals processing

This paper deals with the concept of GNSS meta-signal processing, defined as the coherent process of two GNSS signals, broadcast on different carriers, and treated as a single wideband signal. The purpose of the paper is twofold: to analyse the effects on non-idealities on the meta-signal components and to investigate alternative schemes for the actual implementation inside the receiver

Fast analytical methods for the correction of signal random time-shifts and application to segmented HPGe detectors

Detection systems rely more and more on on-line or off-line comparison of detected signals with basis signals in order to determine the characteristics of the impinging particles. Unfortunately, these comparisons are very sensitive to the random time shifts that may alter the signal delivered by the detectors. We present two fast algebraic methods to determine the value of the time shift and to enhance the reliability of the comparison to the basis signals.Comment: 13 pages, 8 figure

Empowering the Tracking Performance of LEO PNT by Means of Meta-Signals

Global Navigation Satellite Systems (GNSSs) are by far the most widespread technology for Position Navigation and Timing (PNT). They have been traditionally deployed exploiting Medium Earth Orbit (MEO) or Geostationary Earth Orbit (GEO) satellite constellations. To meet future demands and overcome MEO and GEO limitations, GNSSs based on Low Earth Orbit (LEO) constellations have been investigated as a radical system change. Although characterized by a higher Doppler effect, a PNT service supplied by means of LEO satellites can provide received signals that are about 30 dB stronger. Moreover, existing LEO constellations and the forthcoming mega-constellations, which are designed for broadband internet coverage, can be exploited to provide a piggybacked PNT service. With this cost-effective solution, a secondary PNT service might be subject to an economical use of resources, which may result in substantial bandwidth limitations. At the same time, the introduction of meta-signals in the GNSS literature has brought a new receiver signal processing strategy, particularly effective in terms of available bandwidth exploitation. It allows to increase the positioning accuracy exploiting a wideband processing approach, which might be challenging under severe Doppler conditions. A narrowband implementation of the meta-signal concept, namely Virtual Wideband (VWB) can tolerate harsh Doppler conditions while also reducing the processed bandwidth. It is thus more effective when addressing a secondary PNT service, where a limited frequency occupation might be an essential requirement. The aim of this work is to show the applicability of a VWB receiver architecture on signals provided by a piggybacked PNT service, hosted on a broadband LEO constellation. We demonstrate the capability of this implementation to bear high Doppler conditions while empowering the potential of LEO PNT

Overconfidence is a Social Signaling Bias

Evidence from psychology and economics indicates that many individuals overestimate their ability, both absolutely and relatively. We test three different theories about observed relative overconfidence. The first theory notes that simple statistical comparisons (for example, whether the fraction of individuals rating own skill above the median value is larger than half) are compatible (Benoît and Dubra, 2007) with a Bayesian model of updating from a common prior and truthful statements. We show that such model imposes testable restrictions on relative ability judgments, and we test the restrictions. Data on 1,016 individuals' relative ability judgments about two cognitive tests rejects the Bayesian model. The second theory suggests that self-image concerns asymmetrically affect the choice to get new information about oneâs abilities, and this asymmetry produces overconfidence (Kőszegi, 2006; Weinberg, 2006). We test an important specific prediction of these models: individuals with a higher belief will be less likely to search for further information about their skill, because this information might make this belief worse. Our data also reject this prediction. The third theory is that overconfidence is induced by the desire to send positive signals to others about oneâs own skill; this suggests either a bias in judgment, strategic lying, or both. We provide evidence that personality traits strongly affect relative ability judgments in a pattern that is consistent with this third theory. Our results together suggest that overconfidence in statements is most likely to be induced by social concerns than by either of the other two factors.IQ, field experiment, social signaling, self-image, Bayesian updating, overconfidence, numeracy, personality, MPQ

Irrationality is needed to compute with signal machines with only three speeds

International audienceSpace-time diagrams of signal machines on finite configurations are composed of interconnected line segments in the Euclidean plane. As the system runs, a network emerges. If segments extend only in one or two directions, the dynamics is finite and simplistic. With four directions, it is known that fractal generation, accumulation and any Turing computation are possible. This communication deals with the three directions/sp eeds case. If there is no irrational ratio (between initial distances between signals or between speeds) then the network follows a mesh preventing accumulation and forcing a cyclic behavior. With an irrational ratio (here, the Golden ratio) between initial distances, it becomes possible to provoke an accumulation that generates infinitely many interacting signals in a bounded portion of the Euclidean plane. This b ehavior is then controlled and used in order to simulate a Turing machine and generate a 25-state 3-speed Turing-universal signal machin

Performance Limits of GNSS Code-Based Precise Positioning: GPS, Galileo & Meta-Signals

This contribution analyzes the fundamental performance limits of traditional two-step Global Navigation Satellite System (GNSS) receiver architectures, which are directly linked to the achievable time-delay estimation performance. In turn, this is related to the GNSS baseband signal resolution, i.e., bandwidth, modulation, autocorrelation function, and the receiver sampling rate. To provide a comprehensive analysis of standard point positioning techniques, we consider the different GPS and Galileo signals available, as well as the signal combinations arising in the so-called GNSS meta-signal paradigm. The goal is to determine: (i) the ultimate achievable performance of GNSS code-based positioning systems; and (ii) whether we can obtain a GNSS code-only precise positioning solution and under which conditions. In this article, we provide clear answers to such fundamental questions, leveraging on the analysis of the Cramér–Rao bound (CRB) and the corresponding Maximum Likelihood Estimator (MLE). To determine such performance limits, we assume no external ionospheric, tropospheric, orbital, clock, or multipath-induced errors. The time-delay CRB and the corresponding MLE are obtained for the GPS L1 C/A, L1C, and L5 signals; the Galileo E1 OS, E6B, E5b-I, and E5 signals; and the Galileo E5b-E6 and E5a-E6 meta-signals. The results show that AltBOC-type signals (Galileo E5 and meta-signals) can be used for code-based precise positioning, being a promising real-time alternative to carrier phase-based techniques