Перегляд за автором "Lemeshko, O."
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Публікація Analysis of Voice Signal Phase Data Informativity of Authentication System User(ХНУРЕ, 2020) Pastushenko, M.; Krasnozheniuk, Y.; Lemeshko, O.Directions of improving the quality characteristics specific to voice authentication systems in various access systems are analyzed and explored in the article. One of the main directions for improving the quality characteristics of the user authentication systems is the use of phase information of a voice signal. The urgent scientific task of studying new procedures is being solved to refine the estimates of the pitch frequency obtained on the basis of the amplitude-frequency spectrum analysis. The estimates were refined using phase data of the voice signal, as well as estimates of the pitch frequency in the process of obtaining cepstral coefficients. The results are obtained in the course of statistical analyzing the simulation results using experimental voice data of the authentication system user. Phase data of a voice signal allows obtaining adequate and reliable estimates in the process of spectral analysis. However, if there are errors associated with gross errors, for example, when taking the first or second formants for estimating the pitch frequency, preference should be given to the estimate obtained in the process of calculating cepstral coefficients. The presented research results should be used in voice authentication systems, improving speech recognition systems, as well as in solving speaker identification problems.Публікація ICT Disruptive Technologies: Starlink in Ukraine Case(2022) Yeremenko, O.; Lemeshko, O.; Persikov, M.; Lemeshko, V.Currently, disruptive technologies make fundamental changes in markets and industry and are vital in providing critical services. Starlink is such a technology provisioning global Internet access. Thus, there is an urgent need to deploy the Starlink in Ukraine for reliable Internet access to restore destroyed territories.Публікація Inter-domain routing method under normalized Quality of Service based on hierarchical coordination(ХНУРЕ, 2020) Lemeshko, O.; Yevdokymenko, M.; Hu, Z.; Yeremenko, O.The inter-domain routing method under normalized Quality of Service (QoS) based on hierarchical coordination in a Software-Defined Network (SD-WAN, Hybrid SD-WAN) is proposed in the paper. The novelty of the method is that the routing solutions are aimed at ensuring the normalized QoS in terms of average transmission rate and average end-to-end packet delay. The method is based on the use of a decomposition flow-based routing model, which consists of the inter-domain routing interaction and ensuring the normalized QoS conditions that obtained during tensor network modeling. Therefore, the inter-domain QoS routing problem was presented as an optimization problem with a quadratic optimality criterion. A number of numerical examples confirmed the efficiency and effectiveness of the proposed method in terms of providing the normalized QoS within the finite number of iterations. Reducing the number of such iterations helps to decrease the amount of service traffic transferred between routers and SDN controllers at different levels, as well as minimize the time for solving the inter-domain QoS-routing task.Публікація Model of data traffic qos fast rerouting in infocommunication networks(ХНУРЕ, 2019) Lemeshko, O.; Yevdokymenko, M.; Yeremenko, O.The subject of research in the article is the processes of fast rerouting with the protection of the Quality of Service level in infocommunication networks. The aim of the work is the development of a mathematical model of Fast ReRouting with the protection of the Quality of Service level by the bandwidth and probability of packet loss for data traffic. The following tasks are solved in the article: development and research of a fast rerouting flow-based model with the protection of the Quality of Service level of data traffic in the infocommunication network. The following methods are used: the graph theory, the teletraffic theory, the queuing theory, and mathematical programming methods. The following results were obtained: the fast rerouting flow-based model was developed and investigated, which, due to the introduced protection conditions on indicators of bandwidth and packet loss probability, allows providing the Quality of Service along both the primary and backup multipath. Conclusions: Within the framework of the proposed flow-based model, the fast rerouting technological task was formulated as an optimization problem with the constraints of the conditions of implementation of the multipath routing strategy, conditions of flow conservation, and conditions of protection of the link, node, and level of Quality of Service in terms of bandwidth and packet loss probability. The application of this solution contributes to the optimal use of the available network resource while providing the specified level of Quality of Service in terms of bandwidth and probability of packet loss along both the primary and backup routes in the case of a failure of the infocommunication network elements. The proposed flow-based model can be used as the basis of the algorithmic software of existing routers and/or controllers of Software-Defined Networks, which are responsible for the calculation of the primary and backup paths in the fast rerouting of data traffic sensitive to such Quality of Service indicators as bandwidth and packet loss probability.Публікація Network Security Approach based on Traffic Engineering Fast ReRoute with support of Traffic Policing(CEUR-WS, 2021) Lemeshko, O.; Yeremenko, O.; Yevdokymenko, M.; Shapovalova, A.; Lemeshko, V.The work is devoted to the approach development and investigation of the network security providing based on Traffic Engineering Fast ReRoute with support of Traffic Policing. The corresponding flow-based mathematical model has been developed where the technological task of secure fast rerouting was presented in the form of a linear programming problem. The novelty of the proposed model is the modification of load balancing conditions and bandwidth protection during fast rerouting, which in addition to the Quality of Service, also considers the probability of compromising the link as an indicator of network security. The routing solutions obtained within the proposed model are aimed at reducing the overload of communication links with a high probability of compromising by redistributing traffic for transmission through more secure network links. The advantage of the proposed solution is that in the conditions of congestion the load balancing is realized on the principles of Traffic Engineering and, if necessary, differentiated limitation of the load entering the network. An additional advantage of the proposed optimization model is its linearity, which focuses on the low computational complexity of the corresponding protocol implementation in practice. Numerical research of the Secure TE-FRR-TP model has confirmed the adequacy and efficiency of routing solutions made on its basis, both in terms of ensuring network security, resilience, and load balancing with traffic policing based on priorities.Публікація Results of an Experimental Study of the Fault-Tolerant Routing Method with the GLBP Protocol(Eskişehir Technical University, 2022) Lemeshko, O.; Yeremenko, O.; Kruglova, A.; Zhuravlyova, A.; Lemeshko, V.; Persikov, M.This work proposes the results of an experimental study of a fault-tolerant routing method in an infocommunication network. The method implements proactive and reactive protection of the default gateway to provide a high level of network fault tolerance. Therefore, method is based on solving an optimization problem related to calculating primary and backup routes and determining the order of balancing the load incoming to edge routers from access networks. If one of the routers creating the virtual default gateway fails, the method changes the load balancing order between the functional border routers. Causes of failure can include overloading, low equipment reliability, hardware and software router failures, and violation of their network security level (compromise). The method considers the flow-based nature of network traffic, and the optimality criterion of routing solutions under Traffic Engineering is a minimum upper bound of network link utilization. To evaluate the effectiveness of the solutions, they were implemented on Cisco equipment. In the lab experiment, the Gateway Load Balancing Protocol functionality was used. Based on this fault-tolerant routing protocol, it is possible to set weighting coefficients administratively, the value of which affects the order of load balancing on the border routers. During the experiment, the weighting coefficients were adjusted not heuristically but according to the calculations obtained by the studied fault-tolerant routing method. The results of the study confirmed the effectiveness of the proposed solution. Ensuring optimal load balancing between border routers compared to the solution based on multipath routing, but without access layer balancing, improved network performance by 25.45% and reduced the upper bound of network link utilization by an average of 63.77 %. Lowering the utilization upper bound positively affects the quantitative values of the main Quality of Service indicators – the average end-to-end delay, jitter, and packet loss probability.