Positioning precision of GPS/Galileo integration in Vietnam

The design of Galileo has been conceived so as to facilitate its possible joint use with GPS thus contributing to a favorable multi-GNSS environment. Evaluating the performances of such multi-GNSS combination is crucial for end users to assess the quality of obtainable PVT and the easiness of interoperability of the two systems. In this paper, we evaluate the GPS/Galileo integration performances in terms of estimated precision in position determination and in terms of availability of the service. Results obtained from real data are presented and show that there is an improvement of both these criteria when the two systems are jointly used

User Scheduling for Precoded Satellite Systems with Individual Quality of Service Constraints

Multibeam high throughput satellite (MB-HTS) systems will play a key role in delivering broadband services to a large number of users with diverse Quality of Service (QoS) requirements. This paper focuses on MB-HTS where the same spectrum is re-used by all user links and, in particular, we propose a novel user scheduling design capable to provide guarantees in terms of individual QoS requirements while maximizing the system throughput. This is achieved by precoding to mitigate mutual interference. The combinatorial optimization structure requires an extremely high cost to obtain the global optimum even with a reduced number of users. We, therefore, propose a heuristic algorithm yielding a good local solution and tolerable computational complexity, applicable for large-scale networks. Numerical results demonstrate the effectiveness of our proposed algorithm on scheduling many users with better sum throughput than the other benchmarks. Besides, the QoS requirements for all scheduled users are guaranteed.Comment: 6 pages,2 figures, Accepted to present at PIMRC 202

User Scheduling and Power Allocation for Precoded Multi-Beam High Throughput Satellite Systems With Individual Quality of Service Constraints

For extensive coverage areas, multi-beam high throughput satellite (HTS) communication is a promising technology that plays a crucial role in delivering broadband services to many users with diverse Quality of Service (QoS) requirements. This paper focuses on multi-beam HTS systems where all beams reuse the same spectrum. In particular, we propose a novel user scheduling and power allocation design capable of providing guarantees in terms of the individual QoS requirements while maximizing the system throughput under a limited power budget. Precoding is employed in the forward link to mitigate mutual interference among the users in multiple-access scenarios over different coherence time intervals. The combinatorial optimization structure from user scheduling requires an extremely high cost to obtain the global optimum even when a reduced number of users fit into a time slot. Therefore, we propose a heuristic algorithm yielding a good trade-off between performance and computational complexity, applicable to a static operation framework of geostationary (GEO) satellite networks. Although the power allocation optimization is signomial programming, non-convex on a standard form, the solution can be lower bounded by the global optimum of a geometric program with a hidden convex structure. A local solution to the joint user scheduling and power allocation problem is consequently obtained by a successive optimization approach. Numerical results demonstrate the effectiveness of our algorithms on GEO satellite networks by providing better QoS satisfaction combined with outstanding overall system throughput

The BELS Pproject: an opportunity for setting collaboration links between Europe and South East Asia in the field of GNSS

In 2016 the European Global Navigation Satellite System (EGNSS) Galileo should start initial services that will make it available for practical use together with other existing Global Navigation Satellite Systems (GNSS). South East Asia (SEA), which is the Region in the world with the highest multi-GNSS coverage, but has not developed any of them, is the ideal place to promote EGNSS solutions and related technologies to facilitate business while supporting sustainable development. This paper describes the opportunities offered by the project BELS to companies, institutions, researchers from Europe and SEA working in the field of GNSS. The project is funded by the European GNSS Agency (GSA) under the European Union’s Research Framework Programme Horizon 2020.

Local Government Law

Ionospheric scintillation causes rapid fluctuations of measurements from Global Navigation Satellite Systems (GNSSs), thus threatening space-based communication and geolocation services. The phenomenon is most intense in equatorial regions, around the equinoxes and in maximum solar cycle conditions. Currently, ionospheric scintillation monitoring receivers (ISMRs) measure scintillation with high-pass filter algorithms involving high sampling rates, e.g. 50 Hz, and highly stable clocks, e.g. an ultra-low-noise Oven-Controlled Crystal Oscillator. The present paper evolves phase scintillation indices implemented in conventional geodetic receivers with sampling rates of 1 Hz and rapidly fluctuating clocks. The method is capable to mitigate ISMR artefacts that contaminate the readings of the state-of-the-art phase scintillation index. Our results agree in more than 99.9% within¿±¿0.05 rad (2 mm) of the ISMRs, with a data set of 8 days which include periods of moderate and strong scintillation. The discrepancies are clearly identified, being associated with data gaps and to cycle-slips in the carrier-phase tracking of ISMR that occur simultaneously with ionospheric scintillation. The technique opens the door to use huge databases available from the International GNSS Service and other centres for scintillation studies. This involves GNSS measurements from hundreds of worldwide-distributed geodetic receivers over more than one Solar Cycle. This overcomes the current limitations of scintillation studies using ISMRs, as only a few tens of ISMRs are available and their data are provided just for short periods of time.Peer Reviewe

An Adaptive Bandwidth Notch Filter for GNSS Narrowband Interference Mitigation

The low level of received signals power makes Global Navigation Satellite Systems (GNSS) receivers vulnerable to many classes of disturbing signals. Among them, narrow band interference (NBI) might cause serious receiver performance degradation. Cancellation of NBI can be implemented by using notch filters (NF), which are controlled by two parameters: the notch frequency, which specifies the band center, and the notch bandwidth, which defines the spectrum area to be removed. The literature on the topic focuses on adapting the notch frequency, without estimating the filter bandwidth. This paper proposes a method able to determine both the notch parameters, optimizing the interference suppression. The performance analysis shows a good improvement by using the adaptive bandwidth notch filter

Helicobacter pylori infection and gastroduodenal diseases in Vietnam: a cross-sectional, hospital-based study

<p>Abstract</p> <p>Background</p> <p>The rate of <it>H. pylori </it>infection in Vietnam is reportedly high, but the spectrum of <it>H. pylori</it>-associated gastroduodenal diseases has not been systematically investigated. Moreover, despite the similarities of ethnicity and diet, the age-standardized incidence rate of gastric cancer in the northern city of Hanoi is higher than that in the southern city of Ho Chi Minh, but the reason for this phenomenon is unknown. The virulence of Vietnamese <it>H. pylori </it>has also not been investigated in detail.</p> <p>Methods</p> <p>Individuals undergoing esophagogastroduodenoscopy were randomly recruited. <it>H. pylori </it>infection status was determined based on the combined results of culture, histology, immunohistochemistry, rapid urine test and serum ELISA. Peptic ulcer (PU) and gastroesophageal reflux disease was diagnosed by endoscopy, and chronic gastritis was determined histologically. <it>H. pylori </it>virulence factors were investigated by PCR and sequencing.</p> <p>Results</p> <p>Among the examined patients, 65.6% were infected with <it>H. pylori</it>. The prevalence of infection was significantly higher in those over 40 years of age than in those aged ≤40. Chronic gastritis was present in all <it>H. pylori</it>-infected individuals, 83.1% of whom had active gastritis, and 85.3% and 14.7% had atrophy and intestinal metaplasia, respectively. PU was present in 21% of infected patients, whereas its incidence was very low in non-infected individuals. The prevalence of PU was significantly higher in Hanoi than in Ho Chi Minh. The prevalence of <it>vacA m1</it>, which has been identified as an independent risk factor for PU in Vietnam, was significantly higher among <it>H. pylori </it>isolates from Hanoi than among those from Ho Chi Minh.</p> <p>Conclusions</p> <p><it>H. pylori </it>infection is common in Vietnam and is strongly associated with PU, active gastritis, atrophy and intestinal metaplasia. <it>vacA m1 </it>is associated with an increased risk for PU and might contribute to the difference in the prevalence of PU and gastric cancer between Hanoi and Ho Chi Minh.</p

A differential joint data/pilot strategy for high sensitivity Galileo E1 signal acquisition

Global Navigation Satellite Systems (GNSS) with the ability to provide accurate positioning and timing information have become very important for many essential applications of both military and civil purposes. Toward the objective of a high sensitivity GNSS receiver architecture capable of operating anywhere at anytime, this paper introduce a new acquisition strategy to adapt with the problem of low received signal power in indoor environments. The strategy combines the proved advantages coming from joint data/pilot acquisition strategies and differential integration technique to further improve the robustness of the acquisition process. Analytical expressions as well as Monte Carlo simulations in indoor scenarios are presented to describe and prove the strategy improvement with respect to other strategies in literature