Use of the Karhunen-Loève Transform for interference detection and mitigation in GNSS

Improving the Global Navigation Satellite System (GNSS) receiver robustness in a radio interfered environment has been always one of the main concerns for the GNSS community. Due to the weakness of the signal impinging the GNSS receiver antenna, GNSS receiver performance can be seriously threatened by the presence of stronger interfering signals. In these scenarios, classical interference countermeasures may fail due to the fact that interference detection and removal process causes also a non-negligible degradation of the received GNSS signal. This paper introduces an innovative interference detection and mitigation technique against the well-known jamming threat. This technique is based on the use of the Karhunen-Lo`eve Transform (KLT) which allows for the representation of the received interfered signals in a transformed domain where interference components can be better identified, isolated and removed, avoiding significant degradation of the useful GNSS signal

Use of the Wavelet Transform for Interference Detection and Mitigation in Global Navigation Satellite Systems

Radio frequency interference detection and mitigation are becoming of paramount importance due to the increasing number of services and applications based on the position obtained by means of Global Navigation Satellite Systems. A way to cope with such threats is the implementation in the receiver of advanced signal processing algorithm able to raise proper warning or improve the receiver performance. In this paper, we propose a method based on the Wavelet Transform able to split the useful signal from the interfering component in a transformed domain. The wavelet packet decomposition and proper statistical thresholds allow the algorithm to show very good performance in case of multiple pulse interference as well as in the case of narrowband interference, two scenarios in which traditional countermeasures might not be effective

Advanced signal processing techniques for interference removal in Satellite Navigation Systems

This thesis investigates the use of innovative interference detection and mitigation techniques for GNSS based applications. The main purpose of this thesis is the development of advanced signal processing techniques outperforming current interference mitigation algorithms already implemented in off-the-shelf GNSS receivers. State-of-the-art interference countermeasures already investigated in literature, which process the signal at the ADC output, provide interference components suppression in the time domain or in the frequency domain, thus leading to a significant signal degradation in harmful interference scenarios where the GNSS signals spectra at the receiver antenna is completely jammed by external intentional or unintentional RFI sources. The proposed advanced interference countermeasures overcome such a limit, since they are based on particular signal processing techniques which manipulate the received samples at the ADC output, providing a representation in new domains where interference component can be better detected and separated from the rest of the signal, minimizing the useful signal distortion even in presence of multiple interference sources. At the cost of an increased computational complexity, such techniques can be optimized for increasing the sensitivity and the robustness of GNSS receiver merged in harmful environments. The work of this thesis addresses the design of such techniques by means of theoretical analyses, their performance assessment by means of simulation and their validation by means of synthetic and real GNSS data. Furthermore performance comparison with more traditional interference countermeasures is also presented considering a variety of harmful interference scenarios. In addition to the investigation of such new interference countermeasures, part of the thesis deals with the limit of current interference suppression technique, such as the pulse blanking, and its impact on the data demodulation performance. A very general investigation of the pulse blanking impact on the data demodulation performance for un-coded BPSK DSSS is provided. Then, the analysis focuses on the assessment of the navigation data demodulation performance for the current SBAS, then providing a proposal for system improvements, in terms of robustness and data rate increase, in future SBAS generation. Among the different interference scenarios considered, the thesis focuses on the potential interference environment expected in aviation context, since the Galileo E5 and GPS L5 bands, where the future GNSS based aviation services will be broadcast, are shared with other ARNS broadcasting strong pulsed interfering signals, which may seriously threat the on-board GNSS receiver operations . For such scenarios, simulation and analytic models are discussed and used as benchmark cases for assessing the mitigation techniques, in terms of SNR gain and data demodulation capability. The presence of interference (mitigated or not) causes a loss in the carrier to noise density ratio CN0 value for the received signal. For this reason, in order to reliably deal with such signals, the GNSS receiver must be able to feature high-sensitivity algorithms at the acquisition and tracking stages. For this reason the last part of the thesis investigates HS acquisition schemes for very weak GNSS signal detection. In particular, the purpose of this part of the work is to present a theoretical methodology for the design of an acquisition scheme capable of detecting signal down to 5 dB-Hz. The analysis carried out assuming the presence of assistance information which allows the receiver employing long coherent integration time (order of seconds). The particular scenario of the GNSS space environment is taken into consideration and the analysis is also focused on the definition of the requirements on the accuracy for potential Doppler aiding sources at the receiver level. The theoretical analysis is also supported by fully software simulatio

Context-aware Peer-to-Peer and Cooperative Positioning

Peer-to-peer and cooperative positioning represent one of the major evolutions for mass-market positioning, bringing together capabilities of Satellite Navigation and Communication Systems. It is well known that smartphones already provide user position leveraging both GNSS and information collected through the communication network (e.g., Assisted-GNSS). However, exploiting the exchange of information among close users can attain further benefits. In this paper, we deal with such an approach and show that sharing information on the environmental conditions that characterize the reception of satellite signals can be effectively exploited to improve the accuracy and availability of user positioning. This approach extends the positioning service to indoor environments and, in general, to any scenario where full visibility of the satellite constellation cannot be grante

Structural health monitoring and earthquake early warning: preliminary studies for application in eastern Sicily

In this work, the reduction of seismic hazard in eastern Sicily is addressed by both studying the fundamental resonant frequency of strategic buildings through low cost geophysical investigation techniques, and exploring a practical approach to earthquake early warning EEW) system. The fundamental period and the corresponding amplification of some selected strategic buildings has been estimated using ambient vibration and earthquake data. We analyzed the basic dynamic parameters of buildings chosen as target, by using continuous vibration measurements at different floors. The dynamic behavior of structures was evaluated considering both small strains induced by ambient vibrations and larger excitation levels due to the earthquakes occurrence. A practical approach to earthquake early warning in the investigated area was dealt with by using empirical relationships between parameters measured on the initial portion of seismic recordings and related to the earthquake magnitude and peak ground motion. In particular, we performed the first preliminary tests by using empirical relationships calibrated for the considered area and taking into account the geometry of the existing permanent seismic network deployed in the eastern Sicily. The estimated relationships have been used to provide onsite warning around a given seismic station and evaluate the potential damaging effects. The joint of EEW system and geophysical investigation shown in this work may be deemed a useful guide for the future implementation of the in real time seismic monitoring in the region.This work has been supported by the following project: “Attività di sviluppo sperimentale finalizzata alla riduzione del rischio sismico nella Sicilia Orientale” inside the PO-FESR 2007-2013 Sicilia; MED-SUV funded from the European Union Seventh Framework Programme (FP7) under Grant agreement n°308665. This work is sponsored by European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement n° 798480. We are thankful to Salvatore Rapisarda and Danilo Contrafatto to support us in the field work

Seismological constraints for the dyke emplacement of the July-August 2001 lateral eruption at Mt. Etna volcano, Italy

In this paper we report seismological evidence regarding the emplacement of the dike that fed the July 18 - August 9, 2001 lateral eruption at Mt. Etna volcano. The shallow intrusion and the opening of the eruptive fracture system, which mostly occurred during July 12, and July 18, were accompanied by one of the most intense seismic swarms of the last 20 years. A total of 2694 earthquakes (1 £ Md £ 3.9) were recorded from the beginning of the swarm (July 12) to the end of the eruption (August 9). Seismicity shows the upward migration of the dike from the basement to the relatively thin volcanic pile. A clear hypocentral migration was observed, well constraining the upwards propagation of a near-vertical dike, oriented roughly N-S, and located a few kilometers south of the summit region. Earthquake distribution and orientation of the P-axes from focal mechanisms indicate that the swarm was caused by the local stress source related to the dike intrusion

Congenital myopathies: Clinical phenotypes and new diagnostic tools

Congenital myopathies are a group of genetic muscle disorders characterized clinically by hypotonia and weakness, usually from birth, and a static or slowly progressive clinical course. Historically, congenital myopathies have been classified on the basis of major morphological features seen on muscle biopsy. However, different genes have now been identified as associated with the various phenotypic and histological expressions of these disorders, and in recent years, because of their unexpectedly wide genetic and clinical heterogeneity, next-generation sequencing has increasingly been used for their diagnosis. We reviewed clinical and genetic forms of congenital myopathy and defined possible strategies to improve cost-effectiveness in histological and imaging diagnosis

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

Performance assessment of wavelet based techniques in mitigating narrow-band interference

New Global Navigation Satellite Systems (GNSS) in addition to the current American Global Positioning System (GPS) and the Russian GLONASS are being developed leading the GNSS world towards a new era where a wider plethora of services and signals will be available for the end user. The majority of such services needs high accuracy and reliability provided by the navigational interoperable systems. However, intentional and unintentional interference represent one of the main causes of accuracy degradation, and as a consequence, they are a threat to GNSS based application. This paper focuses on a performance assessment of an innovative interference mitigation algorithm based on the use of the wavelet transform, targeting narrow-band interference. The paper will assess the capability of the representation in the time-scale domain to split the interference component and the useful signal thus allowing for a removal of most of the interfering power. Performance are assessed with respect to the interference bandwidth and carrier frequency offset, the number of decomposition levels and the effect of different wavelet families

Classical digital signal processing countermeasures to interference in GNSS

Reliable 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