The paper presents a novel measurement technique of the parameters of erbium-doped fibers for modeling EDFA ampfiers in DWDM systems. A distinctive feature of the proposed measurement technique is the elimination of the effect of losses introduced by the passive components of the measuring schemes on the measurement results.

At present distributed optical fiber acoustic sensors are needed for various applications. Those systems can be realized using polarization optical reflectometry. External mechanical action on optical fiber causes local birefringence changes and variations of optical axis orientation. Thus, analysis of polarized backscattered characteristics can be applied for detection and estimation of acoustic action parameters. Mathematial model of polarization characteristics of optical fiber and results of competer simulation are represented in paper

The design of a microstructured fiber with a core of 35 μm in diameter and a trigonal rotational symmetry, providing more than 50 % discrimination of the higher-order mode components, is proposed and numerically analyzed. In particular, by comparing the values of the effective area and the spatial intensity distribution of the fundamental and most competitive higher-order modes, it is shown that optical elements with a hole ratio of small and large diameter d₂/d₁ = 0,40 within the considered symmetry are capable of maintaining a quasi-single-mode regime of operation in the passive and active performance at the wavelength of 1550 nm.

This article describes the relevance of expanding mobile object localization service area using wireless technologies, as well as improving the accuracy of localization. In order to solve this problem, has been developed a new algorithm of mobile object positioning data integration from several wireless systems giving an opportunity for mobile object localization both at open space and indoors. Efficiency of the developed algorithm was tested by the prototype of a hybrid positioning system. The usage of the algorithm for integrating data from different positioning systems allows not only to solve the problem of a mobile object location in junction region - from open space to indoor, but also to improve the accuracy of determining its true location.

The article is devoted to the analysis of the adjacent-channel interference effects in the IEEE 802.11n/ac networks. In particular, a method is proposed for estimating the modulation and coding rate change as a function of the signal-to-noise ratio degradation in the adjacent channel interference conditions. A number of work scenarios have been selected, for which calculations have been performed, showing the estimated degradation of the data rate. In particular, a comparison of several common frequency plans for IEEE 802.11n/ac networks was made and their effectiveness was estimated from the perspective of adjacent-channel interference. Thus, the impact of extraneous networks has been estimated. The proposed method provides the opportunity to estimate the efficiency of the channel plan selected in order to improve the network operation.

The paper presents a dual basis based algorithm for processing and determining the initial states of the shift registers that form the Gordon-Mills-Welch (GMW) wideband sequences, which are characterized by their greater number and higher structural secrecy than the widely used M sequences. It is shown that the proposed algorithm, in contrast to the known ones, allows one to determine arbitrary initial states of shift registers, which expands the possibilities of using composite wideband GMW sequences for solving various problems when transmitting information via communication channels with noise.

One of the main parameters of radio receiver is sensitivity, which is limited from the bottom side by its own noise. To correctly calculate this parameter in digital radio receivers, it is necessary to determine the noise figure of the digital signal processing unit, the main part of which will be digital filters. This article proposes a method for estimating the minimum bit width of the signal at the output of the filter decimator, in which the contribution of noise caused by truncation of the discharges at the out-put does not have a large effect on the signal- to-noise ratio.

A computer-based static model of high-power field-effect transistors designed to operate in the large excitation signal mode is proposed (in switch mode operation). Based on a static model, a dynamic model is constructed, describing the processes in switch mode transistor circuits. Modeling of radio-frequency generators on GaN-transistors with a switching frequency of 1 GHz has been carried out.

The article presents the results of an experimental investigation of the transfer of multimedia content for augmented reality applications based on a wireless sensor network. I EEE 802.15.4 and ZigBee protocol, as well as IEEE 802.11 (WiFi) are considered as a data transmission technology in a wireless sensor network. The choice of these technologies allows the interaction of Internet of Things devices with each other with the possibility of self-organization and delivery of data for augmented reality applications by relaying through intermediate nodes. In the first part of the article, the features of the transmission of voice and images through a network fragment are experimentally identified. During voice transmission, different languages are considered and the quality of perception at the receiving side is determined. In the second part of the article, the features of data transmission through intermediate nodes are experimentally identified for this purpose, full-scale and simulation modeling are used. On the basis of the conducted research and subsequent analysis, the dependences of the network operation parameters on the number of nodes in the network and the number of transitions are presented.

In this article positioning accuracy limits evaluation of radio emission sources using Time Difference of Arrival and Angle of Arrival methods are investigated. Different accuracy limits estimation metrics, such as Cramer-Rao lower band and Circular Error Probability, are presented. Accuracy limits estimation values, that depend on radiation sources position and its amount, are analyzed and analysis results as graphs in MATLAB are shown.

Audio signal with embedding of information based on modulated reverberation is considered. The goal of such stegosystem commonly is to provide a copy right protection by digital watermarking but sometimes may be interesting also to detect a fact of hidden signal presence by means of steganalysis. Detecting of such stegosystems occurs impossibly when it is executed either by a listening of audio signal or by a observation of signal wave form if deph of embedding is very small. Therefore we propose a new detection algorithm based on properties of modulated reverberation. A performance evaluation of such algorithm is investigated by simulation in terms of the probability of missimg and the probability of false alarm.

Modern wireless communication systems are increasingly penetrating into the millimeter wave rangres. Therefore, there is a need to develop reliable methods for calculating the characteristics of the wave propagation in the millimeter wave bands under various conditions. In this research we investigate the possibility of using the deterministic methods based on the numerical solution of the wave equation. This approach gives an opportunity to calculate and visualize such effects as diffraction, scattering, attenuation and refraction of the radio waves. Specific spatial structure of the radio channel can be taken into account. The well-proven parabolic equation method is used. The modern approaches to the numerical solution of the parabolic equation and the features of their application to the propagation of millimeter waves are considered. Numerical examples under various propagation conditions are given.

An analytical review of known methods for increasing the contrast of matrices of joint distributions based on information about their entropy is presented. The possibilities of the Hough transform. Justified the transition to joint transformations of the Wigner-Hough Theoretical and practical results confirming the increase of the signal components contrast in the time-frequency space are presented. Examples of modeling are given. The advantages and limitations of these approaches are shown.

There are papers in which improving the air radio communication networks. However, this improvement of the networks is not related to gist of the target tasks that are performed with special purpose aircrafts. At the same time, the main task of an air defense aircraft is to point the aircraft at an air target. The purpose of the paper is to formalize and study the impact of the timeliness of command transmission in the network on the guidance probability of the aircraft on the target.