Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-Photon Systems

The article is devoted to issues related to the propagation and transformation of vortexes in the optical range of frequency. Within the framework of the traditional and modified model of slowly varying envelope approximation (SVEA), the process of converting vortex beams of the optical domain into vortex beams of the terahertz radio range based on nonlinear generation of a difference frequency in a medium with a second-order susceptibility is considered. The modified SVEA splits a slowly varying amplitude into two factors, which makes it possible to more accurately describe the three-wave mixing process. The theoretical substantiation of the rule of vortex beams topological charges conversion is given—the topological charge of the output radio-vortex beam is equal to the difference between the topological charges of the input optical vortex beams. A numerical simulation model of the processes under consideration has been implemented and analyzed.

THROUGHPUT INCREASE IN THE OFFICE LI-FI SYSTEM

Background. Wi-Fi has many disadvantages, such as how the maximum bandwidth is limited by the frequency of the range. The work uses Li-Fi technology, which uses visible light for data transmission. The frequency range of Li-Fi is 1000 times greater than the entire radio range. Feedback is used to increase the throughput. But the feedback decreases the bandwidth of the downstream signal. Objective. The purpose of the paper is to analyse what parameters are advisable to change to increase the throughput of the Li-Fi system. Methods. Study of the simulated dependence of the optimal interval change for using the feedback, and using this interval plot the dependence of the throughput on the change in the parameters of the Li-Fi system with a mobile user. Results. With an increase in the area of the photodiode and its refractive index, the throughput increases. As the receiver speed increases, the throughput decreases slightly <0.1%. Reducing the angle of the photodiode field of view and the half-angle of radiation significantly increases the throughput (by 50%) only when decreasing to small angles (<10 °). Conclusions. It is advisable to make photodiode from a material with a high refractive index, with a big area. Since mobile devices are often used in the office Li-Fi network, it is not advisable to reduce the receiver's viewing angle, as well as to reduce the half-angle of radiation. It may also be beneficial to give mobile users more download throughput than upload throughput.

Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-photon Systems

The article is devoted to issues related to the propagation and transformation of vortexes in the optical range of frequency. Within the framework of the traditional and modified model of slowly varying envelope approximation (SVEA), the process of converting vortex beams of the optical domain into vortex beams of the terahertz radio range based on nonlinear generation of a difference frequency in a medium with a second-order susceptibility is considered. The modified SVEA splits a slowly varying amplitude into two factors, which makes it possible to more accurately describe the three-wave mixing process. The theoretical substantiation of the rule of vortex beams topological charges conversion is given &ndash; the topological charge of the output radio-vortex beam is equal to the difference between the topological charges of the input optical vortex beams. A numerical simulation model of the processes under consideration has been implemented and analyzed.

Formation and development of the Ukrainian network of meteor radio observations

During the decade of research, the Research Institute “Mykolaiv Astronomical Observatory” (RI “MAO”) developed hardware and software for monitoring, extracting, and calculating the parameters of meteor phenomena using the forward scattering by meteor ionized trail of the signals of over-the-horizon FM-stations broadcasted in the frequency range of 88—108 MHz. This allowed creating a network of observations of meteor phenomena in the radio range, which consists of six stations located in Mykolaiv (three stations), Rivne, Lviv, and Hlukhiv. The stations have identical hardware and software. Yagi-Uda antennas with six or eight horizontal vibrators and SDR receivers based at RTR2832U microchip are used to receive radio signals. The station software performs continuous registration and analysis of received radio signals at the output of quadrature detectors of the receivers, automatic detection of moments of appearances of meteor reflections, formation, and sending by e-mail daily reports on detected meteor phenomena. Equipment setup and current monitoring of stations operations are carried out by the RI «MAO» using remote access to station computers via the Internet. Monthly reports on the number of meteor events recorded by each station are posted on the site of Radio Meteor Observation Bulletin (RMOB). The article presents the results, obtained by the network in 2017—2019, confirming a correspondence of daily variations in the number of meteors registered by network stations, to the known dependence (observation of meteors in the apex and antapex), as well as a correspondence between the expected characteristics (in time and intensity) of three meteor showers (Perseids, Geminids and Quadrantids) and that had been obtained by the network. Recommendations are also given in the article for additional research aimed at achieving the main goal, namely, expanding information about meteor phenomena, including the estimating of kinematic parameters (velocities, radiants) of meteoroids and their relationship with potentially hazardous asteroids.

A centrality-based history prediction routing protocol for opportunistic networks

Opportunistic networks are a subclass of delay tolerant networks based on a novel communication paradigm that aims at transmitting messages by exploiting direct contacts among nodes, without the need of a predefined infrastructure. Typical characteristics of OppNet include high mobility, short radio range, intermittent links, unstable topology, sparse connectivity, to name a few. As such, routing in such networks is a challenging task since it relies on node cooperation. This thesis focuses on using the concept of centrality to alleviate this task. Unlike other nodes in the network, central nodes are more likely to act as communication hubs to facilitate the message forwarding. In this thesis, a recently proposed History-Based Prediction Routing protocol is redesigned using this concept, yielding the so-called centrality-based HBPR protocol. The proposed CHBPR is evaluated by simulations using the ONE simulator, showing superior performance compared to HBPR without centrality and the Epidemic protocol with centrality.

A centrality-based history prediction routing protocol for opportunistic networks

Opportunistic networks are a subclass of delay tolerant networks based on a novel communication paradigm that aims at transmitting messages by exploiting direct contacts among nodes, without the need of a predefined infrastructure. Typical characteristics of OppNet include high mobility, short radio range, intermittent links, unstable topology, sparse connectivity, to name a few. As such, routing in such networks is a challenging task since it relies on node cooperation. This thesis focuses on using the concept of centrality to alleviate this task. Unlike other nodes in the network, central nodes are more likely to act as communication hubs to facilitate the message forwarding. In this thesis, a recently proposed History-Based Prediction Routing protocol is redesigned using this concept, yielding the so-called centrality-based HBPR protocol. The proposed CHBPR is evaluated by simulations using the ONE simulator, showing superior performance compared to HBPR without centrality and the Epidemic protocol with centrality.

Assessment of Training Aircraft Crew Exposure to Electromagnetic Fields Caused by Radio Navigation Devices

The paper depicts research concerning the value of the electric component of the electromagnetic (EM) energy determined by the NHT3DL meter by Microrad with the 01E measuring probe during a number of flights made by Aero AT-3 R100, Cessna C172, and Tecnam P2006T fixed wing aircrafts and a Robinson R44 Raven helicopter. The point of reference for the recorded measurement was the normative limits of the electromagnetic field (EMF), which can influence a pilot in the course of a flight. Selected studies of the maximum value recorded by the meter was E = 10.66 V/m when landing at an airfield equipped with the VHF (Very High Frequency) omnidirectional radio range (VOR) approach system. Particular attention has been paid to changes in electric field intensity during the operation and their effects on the type of radio navigation systems as well as communication with the airfield control tower. The obtained results were validated in the Statistica 13.3 software for the purpose of a detailed stochastic analysis of the tested values. Results obtained are subject to the mandatory requirements of Directive 2013/35/EU as well as to the relevant regulations in Poland.