2018. 3rd Issue
Full issue (6,9 MB)
GUEST EDITORIAL minta
László Bacsárdi and Kálmán Kovács
Featured papers of the H-SPACE 2018 conference
In 2018, the annual International Conference on Research, Technology and Education of Space has been held the 4th time. The host was the BME Space Forum operated by the Federated Innovation and Knowledge Centre (EIT) of the Faculty of Electrical Engineering and Informatics at the Budapest University of Technology and Economics (BME) – in cooperation with the Hungarian Astronautical Society (MANT), which is the oldest space association in Hungary. Three selected papers are featured in the current issue of the Infocommunications Journal.
PAPERS OF THE SPECIAL ISSUE
Bernard Adjei-Frimpong and László Csurgai-Horváth
Using Radio Wave Satellite Propagation Measurements for Rain Intensity Estimation
The European Space Agency launched a communication satellite called Alphasat in 2013, with two experimental beacons to carry out a scientific experiment by measurement at frequencies of 19.7 GHz and 39.4 GHz respectively. Propagation through the atmosphere at these frequencies is affected by the resence of atmospheric gases and other particles like water vapour, rain and ice drops. Rain attenuation is the most significant parameter which degrades the performance of the links by absorbing and scattering radio waves that can be determined as the measured received signal power’s deviation from the nominal, non-attenuated level. Rainfall statistical data are also measured and recorded by the propagation terminals to provide additional information to apply prediction methods that require minutes of integration time rain intensity.
Andrea Farkasvölgyi and István Frigyes
Optical transfer in space communication
This paper presents the possibilities of Free-space optical connection (FSO) in space communication in case of satellite-to-spacecraft or satellite-to-satellite link. It summerizes the advantages and disadvantages of optical transmissions in case of near-earth and deep space region. We present the most significant problems during FSO link application and introduce some techniques to eliminate the drawbacks. In this paper, we introduce the use of multi-channel FSO system, which is the most appropriate in order to maximize channel parameters with minimizing the transmission error. It compares available maximum channel parameters of near future space missions. Under special conditions in satellite-earth connection, the usage of the optical link may become very uncertain, because of the strong turbulent medium. We describe conditions under which the optical link can be applied in satellite communication and when it is necessary to effectively modify the optical connection, This article discusses the application of multichannel or more precise diversity systems, which we recommend for space communication.
Máté Galambos and László Bacsárdi
Comparing Calculated and Measured Losses in a Satellite-Earth Quantum Channel
Long distance distribution of quantum states is necessary for quantum communication and large scale quantum experiments. Currently this distance is limited by channel loss. Previous theoretical analisys and proof of concept experiments showed that satellite quantum communication may have lower losses than optical cable based counterparts. Recently the QuESS experiment  realized the first satellite-Earth quantum channel. In this paper we compare heoretical predictions of different mathematical models with experimental results regarding channel loss. We examine the HV-5/7 model, HV-Night model and Greenwood model of optical turbulences, the geometric  and diffraction  models of beam wander and beam widening. Furthermore we take into account the effect of atmospheric gases and aerosols as well as the effect of pointing error. We find that theoretical predictions are largely in the same order of magnitude as experimental results. The exception is the diffraction model of beam spreading where our calculations yielded only one tenth of the measured value. Given the ever changing nature of weather conditions and the changing composition of atmospheric aerosoles we conclude that calculated and measured losses are in good agreement.
PAPERS FROM OPEN CALL
Dániel Péter Kun, Erika Baksáné Varga and Zsolt Tóth
Ontology based Indoor Navigation Service for the ILONA System
An ontology based way finding algorithm is presented in this paper that allows route generation between two separate parts of an indoor environment. The presented ontology provides a flexible way to describe and model the indoor environment, in addition it fits and extends the existing model of the ILONA System. Ontology reasoners provide an efficient way to perform complex queries over the knowledge base. The instances, that are queried by the reasoner, are used to initialize the graph which represents an indoor environment. Due to parameterization of the reasoner, different graphs can be generated from the ontology which makes the way finding algorithm flexible. Thus, the task of indoor way finding was converted into a well-known graph search problem. Dijkstra’s shortest path algorithm is used for route generation in the graph yielded. The algorithm was implemented and tested in the ILONA System and its functioning is demonstrated by real-life scenarios.
Miklós Gábriel Tulics and Klára Vicsi
Automatic classification possibilities of the voices of children with dysphonia
Dysphonia is a common complaint, almost every fourth child produces a pathological voice. A mobile based filtering system, that can be used by pre-school workers in order to recognize dysphonic voiced children in order to get professional help as soon as possible, would be desired. The goal of this research is to identify acoustic parameters that are able to distinguish healthy voices of children from those with dysphonia voices of children. In addition, the possibility of automatic classification is children. In addition, the possibility of automatic classification is examined. Two sample T-tests were used for statistical significance testing for the mean values of the acoustic parameters between healthy voices and those with dysphonia. A two-class classification was performed between the two groups using leave-one-out cross validation, with support vector machine (SVM) classifier. Formant frequencies, mel-frequency cepstral coefficients (MFCCs), Harmonics-to-Noise Ratio (HNR), Soft Phonation Index (SPI) and frequency band energy ratios, based on intrinsic mode functions measured on different variations of phonemes showed statistical difference between the groups. A high classification accuracy of 93% was achieved by SVM with linear and rbf kernel using only 8 acoustic parameters. Additional data is needed to build a more general model, but this research can be a reference point in the classification of voices using continuous speech between healthy children and children with dysphonia.
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