The article presents the results of an experiment to measure the bandwidth of a WI-FI network with a different number of networks on a single channel. The formula for calculating throughput is given.

Keywords: WI-FI network, bandwidth, network speed

The article conentrates on the problem of synchronization the pseudo-noise sequence in direct sequence spread spectrum systems. Authors propose a method for transmitting information and synchronizing signals on a single carrier frequency, which allows data transmission in complex coditions in radio channel. A brief review of existing solutions for time synchronization direct sequence spread spectrum systems is carried out. The proposed solution is considered in terms of data transmission in broadband systems in the conditions of negative signal-to-noise ratio, while the limitations of the usage of this solution are also considered. A simulation of the scheme that implements the proposed synchronization method is carried out, and the requirements for the signal-to-noise ratio in the information and synchronization channels are determined. The proposed method can find application in systems with code division multiplexing, including modern IoT systems.

Keywords: time synchronization, direct sequence spread spectrum, broadband communication systems, Internet of Things, BER

Failures in modern communication networks are a factor affecting the indicators of economic efficiency of the organization. The main objective of the project is to study the failure of network elements in order to improve the reliability and resiliency of communication systems by making changes to its structure. The selected recovery strategy for a failed item can significantly affect reliability performance. Results are important to ensure the required level of fault tolerance with limited operating costs.

Keywords: fault tolerance, high availability, failure, reliability, recovery, simulation

The paper analyzes various planning approaches that are part of the QoS QoS assurance subsystem in LTE networks in situations of network traffic congestion. Using different strategies for different types of traffic allows operators to offer different levels of quality of service for voice users. Evaluations of the efficiency of packet transfer scheduling algorithms are given.

Keywords: LTE, Long-Term Evolution, scheduling algorithms, FIFO, Round Robin, Shortest Job First, Random Early Detection, RED, RR, SJF, QoS, VoIP, CSFB, VoLTE

The article focuses on radiowave propagation in complex conditions combining rough terrain with woodland or urban areas. The estimation of influence of all these factors on signal attenuation may be challenging. Consequently there are no propagation models for such environment for distances up to several kilometers. However by approximating the experimental data on radio wave attenuation it is possible to develop empirical propagation models for specific cases. The authors carried out a series of experiments to measure the level of radio signal at a given distance from the source. Based on the experimental results a hybrid model for rough terrain, wooded and urban areas for ground communications systems was developed.

Keywords: radiowave propagation, UHF, experimental study, rough terrain, urban area, wooded area, empirical model, radiowave attenuation, path loss, ground mobile communication

A wide variety of applications of wireless self-organizing networks and high requirements to their quality make it impossible to create a universal routing protocol that works equally well in all cases. Each time when you deploy a new network, you have to select its parameters, but this is inconvenient and often inefficient. In this article, we propose an add-on algorithm over the AODV routing protocol, which allows you to automatically adapt the protocol parameters to dynamically changing network parameters. The perspective of the proposed approach is shown. The architecture of the neural network allowing to control the routing protocol is proposed, the area of ​​further research is indicated.

Keywords: AODV, routing protocol, adaptive routing, ad hoc network, parametric adaptation, simulation

The authors examine the peculiarities of fiber-optic cable electric parameters changes under the influence of a strong homogeneous alternating electromagnetic field. Variants of the process which can be used to describe the influence of the electromagnetic field on the fiber-optic cable are proposed.

Keywords: Fiber optic cable, electrothermal degradation, kevlar, electrical conduction

This article describes electronic design software tools OrCAD implementation for the quadrature MSK-signals (minimum shift keying) modulator creation. Emulation results are presented: digital and analog signals, the output spectrum. The model is designed to generate MSK-signal and study their changes in various RF paths, using all possible analog-digital circuit simulation of OrCAD. The presented model is parametrized. The determinative model parameters are MSK-signal central frequency and pulse duration of modulation sequence. The input sequence - unipolar digital signal is read from an external text file. Realization of a parametric model of the MSK-signal modulator in OrCAD allows the researcher to quickly and easily change the parameters of the signal and to carry out research directly into the package without resorting to third-party software tools, thereby reducing the complexity and development time. The model can also be used in the study subjects issues concerning digital data transmission.

Keywords: circuit simulation, OrCAD, minimum-shift keying, quadrature modulator, parametric model

In the article authors examine specificities of internal components behavior changing in fiber-optical cable under influence of strong variable uniform electromagnetic field. There are some process variations proposed for describing of obtained results.

Keywords: fiber-optical cable, electrothermal degradation, kevlar, conductivity, open fiber-optical cable, partial discharges, water treeing

This article describes the model of the pseudorandom sequences (PRS) generator developed in OrCAD program suite.The described model is applicable for radio systems modules circuits simulation that are using in the operation a PRS. The PRS generator implementation in OrCAD make possible to change PRS parametres immediately in the program, without using other software. A model specificity is that it is parametrised. Parametrization facilitates model control and that is reduce to a minimum necessary manipulations for changing of PRS type. The model is constructed on the basis of circuitry implementation of the linear feedback shift register (LFSR). For adjustment of model it is enough to instal code words setting starting state a LFSR, parametres of a signal of a clock source and to specify register tap output. As an example, used a 16-bit LFSR to create maximum length PRS, tap sequence {0, 5, 9, 13}. Emulation results are presented.

Keywords: pseudorandom sequence, PRS generator, LFSR, OrCAD, circuit simulation

The authors of the article examine the problem of electrothermal degradation of fiber optical communication lines arranged on the high-voltage power lines pylons. The possible methods of reduction of high-voltage line electric field influence on fiber optical communication lines were studied. There is also the method of possible calculation and choice of optimal suspension place for fiber optical cable on a high-voltage line pylon. This method can be applied for one of the high-voltage line masses disposition cases.

Keywords: electromagnetic field, thermal-electric degradation, fiber-optical communication lines, high-voltage power lines

In this article authors give information about problem of fiber-optical communication lines thermal-electric degradation and its consequences and study main reasons and factors which have an influence upon the degree of thermal-electric degradation. Possible and the most promising research ways are examined in this subject area; they let not only study this subject of  fiber-optical communication lines thermal-electric degradation in detail but to solve this problem in whole.

Keywords: electromagnetic field, thermal-electric degradation, fiber-optical communication lines, FOC-cored static wire, kevlar, electrified railway