SYNTHESIS OF SPECTRALLY AND ENERGY-EFFICIENT SIGNAL-CODE CONSTRUCTIONS FOR MIMO SYSTEMS WITH SIGNALS SPATIAL CODING

Wireless communication systems are considered, the main task of which is to increase their spectral (SE) and energy efficiency (EE) in conditions of limited frequency and energy resources. Additional use of the spatial resource based on flexible and universal methods of signals Space-Time Coding (STC) in MIMO-systems (Multiple Input - Multiple Output) can significantly increase the SE and EE values, as well as significantly improve the capabilities and conditions for EE exchange on SE. The advantages and disadvantages of Orthogonal Space-Time Block Coding (OSTBC) and Non-Orthogonal STBC (NOSTBC) are shown. Two main methods of synthesis of spectrally and energy-efficient information transmission methods are demonstrated. The first method is implemented by creating Perfect-codes that simultaneously achieve maximum diversity and multiplexing gains. The exponential computational decoding complexity of such codes makes it impossible for their practical implementation in mobile terminals at the present stage of development of circuitry. The second method of synthesis is based on improving the simple basic STC methods in terms of increasing the SE and EE by creating Signal-Code Constructions (SCC), which have the advantages of the basic STC methods and are devoid of the disadvantages inherent in Perfect-codes. A technique for the synthesis of SCC is proposed, the essence of which is to determine the priority areas (by the value of the Signal-to-Noise Ratio (SNR)) of using the STC and corresponding signal constellations, which provide the maximum SE for a guaranteed Bit Error Rate (BER). It was found that MIMO 2x2 with Alamouti OSTBC has an advantage in terms of EE over NOSTBC type VBLAST for SE not more than 8 b/s/Hz and SNR under 35 dB, BER not exceeding 10-5. In MIMO 4x4, OSTBC codes are inferior to NOSTBC in terms of EE. VBLAST code allows to provide SE 4 - 8 b/s/Hz at SNR 10 - 20 dB, BER not exceeding 10-5. Based on the results obtained, propositions for further improvement of OSTBC and NOSTBC are formulated.

JOB ORDER INPUT FOR EFFICIENT EXACT MINIMIZATION OF TOTAL TARDINESS IN TIGHT-TARDY PROGRESSIVE SINGLE MACHINE SCHEDULING WITH IDLING-FREE PREEMPTIONS

A schedule ensuring the exactly minimal total tardiness can be found with the respective integer linear programming problem. An open question is whether the exact schedule computation time changes if the job release dates are input into the model in reverse order. The goal is to ascertain whether the job order in tight-tardy progressive single machine scheduling with idling-free preemptions influences the speed of computing the exact solution. The Boolean linear programming model provided for finding schedules with the minimal total tardiness is used. To achieve the said goal, a computational study is carried out with the purpose of estimating the averaged computation time for both ascending and descending orders of job release dates. Instances of the job scheduling problem are generated so that schedules which can be obtained trivially, without the exact model, are excluded. As in the case of equal-length jobs, it has been ascertained that the job order really influences the speed of computing schedules whose total tardiness is minimal. Scheduling two to five jobs is executed on average faster by the descending job order input, where 1 to 3 % speed-up is expected. Further increment of the number of jobs to be scheduled cannot guarantee any speed-up even on average. This result is similar to that in the case of equal-length jobs, but there is no regularity in such an efficient job order input. Without any assurance for a single job scheduling problem, the efficient exact minimization of total tardiness by the descending job order input must be treated as on average only.

OPTIMAL ROUTES SEARCH IN LARGE MAIL NETWORKS

Currently, small postal networks, characterized by the presence of unique links between their structures and communication matrices, are mainly used to meet the needs of the postal service. These networks are constantly being developed and improved, in particular, new regional automated sorting centers are being created that use robotic complexes, machines and devices, mail transportation and processing schemes are complicated, and alternative options for such schemes arise, including alternative options for quantity, location and throughput specified sorting centers, securing postal service objects, sequences and time schedules for their passage, etc. As a result, small mail communication networks are gradually turning into large mail communication networks, a characteristic feature of which is the lack of unambiguous connections between their structures and connectivity matrices, which greatly complicates the search for optimal paths in these networks. In this work, as the prototypes of large postal networks, the lines of the largest undergrounds in the world are used. Although the subways are not intended for transportation and processing of mail, they provide an opportunity to get a real idea of the difficulty of finding optimal paths in large postal networks, to compare and evaluate the effectiveness of search algorithms for such paths in these networks

INCREASE OF STEALTH TRANSMISSION BASED ON TIMER SIGNALS AND LINEAR FREQUENCY MODULATION

Recently, much attention has been paid to the research of the properties and methods of forming complex noise-like signals to increase the noise immunity of radio communication systems operating in the conditions of electronic conflict. Using such signals, the tasks are resolved to improve the noise immunity and the main indicators of transmission stealth (energy, structural and information). For the task of the synthesis noise-like signals using timer signal designs in combination with the method of spreading the spectrum based on linear frequency modulation is proposed. The advisability of using timer signals is justified by their properties, which increase the noise immunity and stealth transmission. In contrast to positional codes, timer signals have more complex structure for construct signal construction. The initial parameters for constructing timer signals allow the formation of various sets of signal constructions. Such variational possibilities of constructing timer signals substantially increase the potential structural stealth of the transmission. Also based on timer signals, noise immunity coding is implemented without additional test elements. In the article A method for synthesizing noise-like signals based on linear frequency modulation and timer signal designs is proposed.

POLARIZATION MODE DISPERSION COMPENSATOR BASED ON ANISOTROPIC OPTICAL FIBER

In this paper, a new method of polarization mode dispersion (PMD), which can significantly limit the speed and range of transmission of fiber optic transmission systems (FOTS), compensation was developed and analyzed. In contrast to the existing types of PMD compensators, in which the optical fiber is subjected to mechanical stresses to create a photoelastic anisotropy, in this work the use of alternative method of creating photoelasticity in optical fiber (OF) by creating a helical ordered rotation of the glass microstructure (ORMG) is proposed. The helical orientation of the microstructure of the OF glass is achieved by acting on the fiber in the process of manufacture (drawing), when it is in a hot state, electromagnetic field, the power lines of which are directed in a circle. I am not sure what this sentence is trying to say. The result is an asymmetry of the dielectric constant of the fiber glass material and therefore the anisotropy of the optical properties. When the optical signal propagates in such OF, there is a double refraction, which is the cause of artificial PMD in the compensator fiber. Compensation is achieved by performing the equality of the modulus and the sign-opposite between the linear path PMD and the PMD of the anisotropic OF with the ORMG. The expression of the calculation of the PMD of the compensator, which depends on the rotation step of the microstructure of the glass, the chemical composition of the OF, the length of the line, the width of the radiation spectrum and the wavelength of the optical signal, and the optical characteristics of the OF, is analyzed, as well as the spectral dependence of polarization mode dispersion for different chemical compositions of the OF. The expression of determining the length of the OF with the ORMG is presented to compensate for the set value of the PMD in the line. The results of the studies made it possible to determine the lengths of the segments of OF with ORMG, which will provide partial or complete compensation of PMD over a wide range of wavelengths and create passive compensators for dispersion.

EMERGENCY CONTROL SYSTEM BASED ON NEURAL NETWORKS AND FUZZY LOGIC

The presented paper investigates the problem of ensuring the safety of modern vessels, represented as complex organizational and technical systems. This study solves the task of diagnosing and predicting the level of ships’ operational reliability using a hybrid expert system based on a combination of a neural network and fuzzy logic. Trends in modern control systems show that they must be adaptive and intelligent. However, these requirements cannot be met by expert systems based only on fuzzy logic. This work explores the possibility of combining neural network modules with fuzzy logic and considers the features of emergency management stages based on the offered hybrid expert system. The input information arrives in a knowledge base through gauges, where it is structured and distributed in the form of performance indicators. Emergency recommendations for the operator are formed as a result of a combination of performance indicators available in the knowledge base. Modules of the neural network and fuzzy logic form a system for assessing a complex technical system’s health based on calculated estimates of the health of technical nodes. In addition, the authors formed a hierarchy of factors affecting the reliability of the system. While developing the knowledge base, critical values for each variable influencing the system performance are set, and when the values are reached, the operation mode becomes an emergency. The authors chose a multilayer perceptron with a layer of recurrent neurons and inputs as fed factors and criteria for performance; one output displays the value of system performance. Prediction of the technical state of the system is made based on time series analysis. The system with six variables was used as a test set, three of which are non-linguistic (efficiency coefficient, temperature, and pressure). The standard linguistic variable, calculated by the neural network, includes speed, fuel consumption, and wear of the node. The fuzzy logic module was used to form recommendations for the prevention or elimination of an emergency.

THE INFLUENCE OF THE MOVEMENT OF IMPURITY IONS ON THE STABILITY OF LEDS

The influence of the motion of impurity centers on the stability of GaInAsP-based light- emitting diodes and their efficiency are studied. The stability and efficiency of the electroluminescence of LEDs is mainly determined by the ratio between the intensities of the radiative and non-radiative recombination of charge carriers. We studied the electroluminescent and electrical characteristics of LEDs. To clarify the degradation mechanism of LEDs, we studied the effect of their current training for 3000 hours at various current densities for stability and efficiency and for their electrical characteristics. It was shown that the degradation of LEDs at low injection levels is associated with the drift of impurity centers near the inhomogeneities of р-л-junctions. It is shown that during the degradation of LEDs, the magnitude of the radiative current component at a fixed voltage varies little. At the same time, nonradiative current components increase significantly. It was established that the growth of nonradiative current components is associated with the drift of mobile impurities to inhomogeneities of the р-л-junction. The kinetics of LED degradation was calculated using certain assumptions. The diffusion coefficient of the ions responsible for the degradation of the diodes is estimated. It is shown that “sudden” LED failures are of the same nature as their gradual degradation. They can occur at a sufficiently high concentration of mobile impurities. The obtained dependences of the radiation intensity on the duration of degradation can be used to estimate the diffusion coefficient of a mobile impurity.

FEATURES AND CONSEQUENCES OF MANIFESTATION OF INFORMATION RISKS AT THE GLOBAL LEVEL IN MODERN CONDITIONS

The article is devoted to the risk analysis associated with the use of information and information technologies. Activation and deployment of “digital transformation programs” are accompanied by the emergence of new or unfamiliar challenges and threats; they have a significant negative impact on all aspects of society and are called as “information risks”. It has been shown that any modern entity with social and economic relations provides a wide range of information risks. The purpose of the research is to identify and substantiate the existing problems of qualitative analysis of the emergence and consequences of global information risks, as well as to develop recommendations for their solution. The analysis of different views according to the problems of global risks has been given. The analysis gives an opportunity to offer a separate group of “global information risks” from a part of global risks. It is shown that this can be determined by: causes and peculiarities of their occurrence and emergence; specific activities in order to reduce the likelihood of their occurrence; exclusion, or mitigation of negative effects of their occurrence; specific requirements for the category, staff and competency of managers who should deal with global information risk management. Recommendations have been offered in order to supplement the existing global risks with a separate group - global information risks and to the list of risks such as “massive fraud and data theft”, “large-scale cyber attacks”, “destruction of critical information infrastructure and networks”. It is necessary to add “global content risks”, “risk of privacy loss (for state and private sectors)”, as well as “risk of confidence loss in the media (sources of information)”. Features of these risks emergence have been considered.

METHODS OF THERMAL-STTMULATED CURRENTS FOR RESEARCH OF IMPURITY SITES AT LTGHT-EMTTTTNG DTODES

Impurity sites in LEDs based on of Gai-xAlxAs for fiber-optic communication lines using thermal-stimulated current method were researched. The causes of the degradation of such diodes are clarified. The installation for research using the method of thermal-stimulated currents is described. Given in p-n junctions based on GaAlAs. The dependence curves of thermal-stimulated currents and temperature are shown at various heating rates. Was made a research of light-emitting diodes degradation by their power supply of current pulses up to 10 A, with a duration of 100 ns and a frequency of 300 Hz, as well as at 50 mA, 20 mA and a temperature of 800C. A connection was found in the process of degradation of LEDs with an increasing of the concentration of impurity sites. The curves of thermal-stimulated currents determined the concentration of impurity sites before and after the degradation of LEDs. It is shown that the main reason for the change in the electrical characteristics of the p-n junctions of the studied samples upon passing a direct current is the accumulation of impurity sites.

THE INFLUENCE OF INFORMATION PROTECTION PROTOCOLS ON THE FORMATION OF THE VALUE OF CRYPTOVALUTE AND ITS OSCILLATIONS

The study is aimed at identifying the influence of information security protocols used in cryptocurrencies on the formation of the value of cryptocurrencies and fluctuations in their value. A comparison is made of the value fluctuations against the US dollar. Attention is paid to transaction security algorithms - protocols for protecting information from outside influence. The reasons for the sharp changes in cost are considered. Considering that the phenomenon called "cryptocurrency" is quite new, but at the same time attractive to many, the study of this phenomenon can be useful both from a practical and scientific point of view. Research for practitioners can have the effect of avoiding unpromising areas in cryptocurrency development. Scientific research could answer what explains the existence of this phenomenon. The article notes that the phenomenon is extremely insufficiently discussed in the scientific community (according to the information that we have). The main means of forming an idea about the phenomenon of cryptocurrencies are separate disparate messages on social networks, and forums of people united by this topic. Probably the phenomenon does not fit well with the classical concept of "money", therefore it is perceived ambiguously. It is little defined how the improvement of software (technical) measures affect the popularity of cryptocurrencies, is there a dependence on other factors? This article examines information security protocols as a factor influencing the popularity of cryptocurrencies. Based on the analysis, it is concluded that there is no direct and unambiguous dependence on the improvement of information security protocols for cryptocurrencies and the demand for them. At the same time, the article analyzes other factors and proposes an improved formula for assessing the potential attractiveness of cryptocurrencies.