It is shown that, in order to increase the compression ratio in the course of statistical arithmetic coding, it is necessary to take into account the conditional probabilities of code symbols when the preceding symbols appear. The problem of obtaining the location of the most significant symbols when encoding the current symbol is solved by calculating the autocorrelation function of the encoded symbols. An algorithm for arithmetic coding and decoding is provided, which takes into account the dependencies between the coefficients of the wavelet transform and the results of modeling its operation.

Results of studies of dynamic energy losses in broadband switch amplifiers of the BD and ABD classes when operating on a hydroacoustic emitter are presented. Relative energy losses in amplifying stages based on silicon (Si) and silicon carbide (SiC) field-effect transistors are compared along with dynamic processes associated with "transistor-diode" through current in switching amplification circuits with Si pulsed reverse diodes and SiC Schottky diodes. The viability of using modern SiC transistors with their own reverse Schottky diodes is demonstrated. Highfrequency components of the low-pass filter current must be taken into account in order to assess the energy performance of the transmitting equipment. Recommendations on the choice of operating modes for the final stages of the switch amplification modules of hydroacoustic radiating paths are offered.

The assignation a particular channel to an access point in large, distributed IEEE 802.11 networks can present a complex challenge. Although the channel can be assigned automatically by the network controller in some cases based on specified settings, it may require human attention when this is not possible. In order to select a frequency plan, it is necessary to understand the advantages of a particular channel configuration and evaluate the resulting effects of adjacent-channel interference at the design stage. A similar problem may arise during WLAN troubleshooting. In this paper, we consider distributed flat wireless networks as regular structures in plane tessellation and propose a method for finding the best channel configurations for the most efficient channel planning of IEEE 802.11 networks, which take the specifics of spectrum use in these networks into account. In addition, we consider the simplest possible solutions for three- and four- channel frequency plans.

The problem of interference mitigation in satellite navigation signals is considered. Construction algorithms for space- and space-frequency adaptive filters are described. The processing of real satellite signals with broadband interference by means of the constructed filters is carried out in MATLAB. As a result of comparing different processing quality indicators, the most efficient filtering algorithms are identified.

An information leakage channel created on the basis of fiber bending when transmitting information over an optical fiber is studied. An increase in the bending diameter of an optical fiber is shown to lead to a decrease in the power of optical radiation proceeding from it. In a bending diameter range from 5 to 20 mm, the highest radiation power was observed for the optical fiber G.655, while the lowest corresponding figure was recorded for G.657. The information leakage channel bandwidth with changed bending diameter is determined for different types of optical fiber. The bandwidth of the information leakage channel is shown to depend on the location of the photodetector used to register optical radiation taken from the bend of the optical fiber.

The process of servicing traffic in a radio communication network in a complex interference environment is studied based on analytical and simulation modeling. A developed analytic-simulation model for servicing real-time traffic in a complex interference environment is described along with an algorithm for calculating a single-channel queuing system with an exponential time distribution between incoming requests and gamma distribution of service time in a channel.

The current technical condition of antenna fields used in short-wave stationary transmitting radio centers is considered. The basic requirements for antenna systems used in radio centers to allow effective operation on routes having a length of 100‒5000 km are formulated. Models for the most common types of HF-band antenna systems constructed using electrodynamic modeling methods, which include logoperiodic, rhombic horizontal double, symmetrical horizontal vibrator, are described together with their energy and non-energy characteristics. Designs for a modified version of an ultra-wide-band logoperiodic structure and active phased array operating in the frequency range of 2–30 MHz are presented. Energy and non-energy parameters of existing and modified antenna systems proposed for replacement are compared. Presented results of track tests using existing and prospective antenna systems operating on a real object include an assessment of the effectiveness of each system on an average-length radio track (2100 km). The developed approach to constructing a high-frequency path of a transmitting radio center using ultra-wide-band pyramidal curved logoperiodic and pin antennas is based on calculated and experimentally obtained results. Active phased antenna arrays with controlled directional patterns developed on their basis are presented along with an appropriate antenna field layout variant.

Thematic justification. When planning HF radio communication using surface waves, it is necessary to determine the signal-to-noise ratio at the inputs of each radio link receiver. Given a sufficiently high ratio, a conclusion can be drawn concerning the effective functionality of the analyzed radio link in a radio communication system. The planning process will be significantly simplified if the radius of the electromagnetic availability zone (REAZ) can be defined for surface waves at each radio station. Thus, the task of developing a methodology for engineering calculation of REAZ is relevant and practically important.

Goal. To develop an estimating technique for engineering calculations of a REAZ based on a surface wave source with a given isotropically emitted signal spectrum density.

Results. A technique for calculation of the radius of the electromagnetic accessibility zone was developed. A general approach for determining the limiting length of radio links of surface waves is proposed, based on the introduced "technical factor of a radio link" concept.

Practical implications. Nomograms for determining the radius of an electromagnetic accessibility zone were constructed. The dependence of the maximum temperature of external noise on frequency in the HF range can be approximated using an analytical expression. The developed frequency dependence of the temperature coefficient of the input of an ShT4N81 antenna is presented in a graphical form. The feasibility of using the proposed technique for solving practical problems is demonstrated on the example of calculating the radius of the electromagnetic accessibility zone of a TTR-2101M radio station for a monopulse direction finder with a ring antenna array consisting of eight elements of the ShT4N81 type.

The second part of the study on 5G NR network positioning technology with meter accuracy modeling is devoted to the procedures for range-difference measurements processing based on configured PRS positioning reference signals with the resulting estimate of the user equipment coordinates based on observed time difference of arrival (OTDOA) of the signals. The software implementation of the procedures for PRS signals primary and secondary processing in the simulation model uses the built-in functions of the 5G Toolbox extension package of the special MATLAB software. The assessment of the positioning accuracy of user devices in 5G NR networks using simulation modeling in the FR1 range shows that the accuracy of coordinate estimates of less than one meter is achieved when increasing the bandwidth from 50 to 60 MHz with the maximum positioning accuracy in the FR2 band in a channel having a bandwidth of 400 MHz and a sampling rate of 491.52 MHz was 0.2 m.

The complexity of ensuring the availability of geoinformation systems resources is due to the volatile structure of the system, the uncertainty of user tasks and destructive influences. This paper proposes methods that allow to halve the probability of information security risk associated with the disruption of resource availability. The effect is achieved by: 1) preserving the required probability of achieving the activity goal of the identification system, regardless of the strength of disruptive influences; 2) by aggregating the performance of individual physical system elements into virtual pools; and 3) by converting internal user task reserves into performance reserves. The performance of the methods was evaluated using a simulation model developed in MATLAB environment.

The paper considers a modification of the well-known algorithm for detecting anomalies in network traffic using a real-time fractal dimension jump estimation method. The modification uses real-time thresholding to provide additional filtering of the estimated fractal network traffic dimension. The accuracy of the current estimate of the fractal dimension and the reliability of anomaly detection in network traffic in online mode is improved by adding extra filtering to the algorithm.