Vol 22, No 2 (2023)
Digital information telecommunication technologies
Limit Bipolar Sequences for Patchwork-Based Robust Digital Audio Watermarking
Abstract
Ensuring the robustness of digital audio watermarking under the influence of interference, various transformations and possible attacks is an urgent problem. One of the most used and fairly stable marking methods is the patchwork method. Its robustness is ensured by the use of expanding bipolar numerical sequences in the formation and embedding of a watermark in a digital audio and correlation detection in the detection and extraction of a watermark. An analysis of the patchwork method showed that the absolute values of the ratio of the maximum of the autocorrelation function (ACF) to its minimum for expanding bipolar sequences and extended marker sequences used in traditional digital watermarking approach 2 with high accuracy. This made it possible to formulate criteria for searching for special expanding bipolar sequences, which have improved correlation properties and greater robustness. The article developed a mathematical apparatus for searching and constructing limit-expanding bipolar sequences used in solving the problem of robust digital audio watermarking using the patchwork method. Limit bipolar sequences are defined as sequences whose autocorrelation functions have the maximum possible ratios of maximum to minimum in absolute value. Theorems and corollaries from them are formulated and proved: on the existence of an upper bound on the minimum values of autocorrelation functions of limit bipolar sequences and on the values of the first and second petals of the ACF. On this basis, a rigorous mathematical definition of limit bipolar sequences is given. A method for searching for the complete set of limit bipolar sequences based on rational search and a method for constructing limit bipolar sequences of arbitrary length using generating functions are developed. The results of the computer simulation of the assessment of the values of the absolute value of the ratio of the maximum to the minimum of the autocorrelation and cross-correlation functions of the studied bipolar sequences for blind reception are presented. It is shown that the proposed limit bipolar sequences are characterized by better correlation properties in comparison with the traditionally used bipolar sequences and are more robust.
Informatics and Automation. 2023;22(2):221-260
221-260
Noise Immunity of Single-Sideband Modulation Signals with a Controlled Carrier Level
Abstract
Single-sideband modulation is actively used in the organization of communication through the ionospheric channel in the decameter range of radio waves. This is due to the fact that transmissions with single-sideband modulation make it possible to minimize the frequency band while maintaining the information transfer rate and at the same time increase the noise immunity of reception in relation to transmissions with amplitude and frequency analog modulation. At the same time, the widespread use of quadrature synthesis technologies has opened up new possibilities for the formation of transmissions with single-sideband modulation without the direct use of filtering procedures. An analysis of the implementation features of the method of quadrature synthesis of signals with single-sideband modulation showed that the introduction of an additional parameter into its procedures will allow you to control the residual level of the carrier wave, and thereby control the noise immunity of the reception. The opened opportunities made it possible to develop a method and a device for generating a single-sideband modulation signal with an adjustable level of the carrier wave that implements it. The technologies of quadrature synthesis of signals of amplitude modulation and single-sideband modulation with the suppressed carrier are considered both at the level of analytical modeling and using a standard quadrature modulator. The necessity of transition to the analytical form of representation of the modulating signal is substantiated. The role and place of the Hilbert converter in the formation of signals with single-sideband modulation are shown. Known technologies for generating single-sideband modulation signals with a stored pilot signal are considered. The possibility of controlling the value of the stored pilot signal at the level of quadrature synthesis procedures is substantiated. An analytical model and, based on it, a structural diagram have been developed that allow one to generate single-sideband modulation signals with an adjustable pilot signal level. The results of analytical modeling are demonstrated. The value of the provided energy gain as a result of regulation by the residual level of the carrier wave is calculated. Approaches to assessing the noise immunity of transmissions with single-sideband modulation are analyzed. An approach is proposed for calculating the bit error probability of SSB transmissions manipulated by discrete oscillations based on the results of energy redistribution between the carrier oscillation and the sideband, determined by the residual pilot signal level. Conclusions and proposals for the practical implementation of the results obtained are formulated.
Informatics and Automation. 2023;22(2):261-288
261-288
Building a Chatbot System to Analyze Opinions of English Comments
Abstract
Chatbot research has advanced significantly over the years. Enterprises have been investigating how to improve these tools’ performance, adoption, and implementation to communicate with customers or internal teams through social media. Besides, businesses also want to pay attention to quality reviews from customers via social networks about products available in the market. From there, please select a new method to improve the service quality of their products and then send it to publishing agencies to publish based on the needs and evaluation of society. Although there have been numerous recent studies, not all of them address the issue of opinion evaluation on the chatbot system. The primary goal of this paper’s research is to evaluate human comments in English via the chatbot system. The system’s documents are preprocessed and opinion-matched to provide opinion judgments based on English comments. Based on practical needs and social conditions, this methodology aims to evolve chatbot content based on user inter-actions, allowing for a cyclic and human-supervised process with the following steps to evaluate comments in English. First, we preprocess the input data by collecting social media comments, and then our system parses those comments according to the rating views for each topic covered. Finally, our system will give a rating and comment result for each comment entered into the system. Experiments show that our method can improve accuracy better than the referenced methods by 78.53%.
Informatics and Automation. 2023;22(2):289-315
289-315
Performance Analysis of Concatenated Coding to Increase the Endurance of Multilevel NAND Flash Memory
Abstract
The increasing storage density of modern NAND flash memory chips, achieved both due to scaling down the cell size, and due to the increasing number of used cell states, leads to a decrease in data storage reliability, namely, error probability, endurance (number of P/E cycling) and retention time. Error correction codes are often used to improve the reliability of data storage in multilevel flash memory. The effectiveness of using error correction codes is largely determined by the model accuracy that exhibits the basic processes associated with writing and reading data. The paper describes the main sources of disturbances for a flash cell that affect the threshold voltage of the cell in NAND flash memory, and represents an explicit form of the threshold voltage distribution. As an approximation of the obtained threshold voltage distribution, a Normal-Laplace mixture model was shown to be a good fit in multilevel flash memories for a large number of rewriting cycles. For this model, a performance analysis of the concatenated coding scheme with an outer Reed-Solomon code and an inner multilevel code consisting of binary component codes is carried out. The performed analysis makes it possible to obtain tradeoffs between the error probability, storage density, and the number of P/E cycling. The resulting tradeoffs show that the considered concatenated coding schemes allow, due to a very slight decrease in the storage density, to increase the number of P/E cycling up to 2–2.5 times than their nominal endurance specification while maintaining the required value of the bit error probability.
Informatics and Automation. 2023;22(2):316-348
316-348
Mathematical modeling and applied mathematics
Properties Investigation of Self-Dual Combinational Devices with Calculation Control Based on Hamming Codes
Abstract
A new approach to the synthesis of self-checking devices is considered, based on the control of calculations in testing objects using Hamming codes, the check bits of which are described by self-dual functions. In this case, the structure operates in a pulsed mode, which is actually based on the introduction of temporal redundancy when building a self-checking device. This, unfortunately, leads to some decrease in performance, however, it significantly improves the characteristics of controllability, which is especially important for devices and systems of critical use, the input data for which does not change so often. A brief review of methods for constructing built-in control circuits based on the self-duality property of calculated functions is given. The basic structures of the organization of built-in control circuits are given. The proposed ways of developing the theory of synthesis of built-in control circuits are based on checking whether or not the calculated functions belong to a class of self-dual Boolean functions. All possible values of the number of data bits for Hamming codes have been established. They will have the property of the self-duality of functions describing control bits. En-coders of such Hamming codes will be self-dual devices. Since the functions of the check bits of Hamming codes are linear, in order for them to be self-dual, it is necessary that an odd number of arguments be used in each of them. It is proved that the number of bits of code words of Hamming codes with self-dual check functions is equal to n=3+4l, l∈N0. The results of the simulations self-dual devices with built-in control circuits along two diagnostic parameters in the Multisim environment are presented. A method is proposed for modification of the structure of calculation control along two diagnostic parameters, which allows to use any linear block code (not necessarily Hamming code). It is based on retrofitting the encoder with a device for converting functions into self-dual ones. In fact, this is a code modification device. It is proved that to obtain a modified Hamming code with self-dual control functions for n≠3+4l, l∈N0; cases, it is enough to add modulo M=2 the non-self-dual control function with the function of the high data bit.
Informatics and Automation. 2023;22(2):349-392
349-392
Optimization of the Regression Ensemble Size
Abstract
Ensemble learning algorithms such as bagging often generate unnecessarily large models, which consume extra computational resources and may degrade the generalization ability. Pruning can potentially reduce ensemble size as well as improve performance; however, researchers have previously focused more on pruning classifiers rather than regressors. This is because, in general, ensemble pruning is based on two metrics: diversity and accuracy. Many diversity metrics are known for problems dealing with a finite set of classes defined by discrete labels. Therefore, most of the work on ensemble pruning is focused on such problems: classification, clustering, and feature selection. For the regression problem, it is much more difficult to introduce a diversity metric. In fact, the only such metric known to date is a correlation matrix based on regressor predictions. This study seeks to address this gap. First, we introduce the mathematical condition that allows checking whether the regression ensemble includes redundant estimators, i.e., estimators, whose removal improves the ensemble performance. Developing this approach, we propose a new ambiguity-based pruning (AP) algorithm that bases on error-ambiguity decomposition formulated for a regression problem. To check the quality of AP, we compare it with the two methods that directly minimize the error by sequentially including and excluding regressors, as well as with the state-of-art Ordered Aggregation algorithm. Experimental studies confirm that the proposed approach allows reducing the size of the regression ensemble with simultaneous improvement in its performance and surpasses all compared methods.
Informatics and Automation. 2023;22(2):393-415
393-415
Discovery of Economic Collusion by Metrics of Quantum Entanglement
Abstract
An effective economy requires prompt prevention of misconduct of legal entities. With the ever-increasing transaction rate, an important part of this work is finding market collusions based on statistics of electronic traces. We report a solution to this problem based on a quantum-theoretical approach to behavioral modeling. In particular, cognitive states of economic subjects are represented by complex-valued vectors in space formed by the basis of decision alternatives, while decision probabilities are defined by projections of these states to the corresponding directions. Coordination of multilateral behavior then corresponds to entanglement of the joint cognitive state, measured by standard metrics of quantum theory. A high score of these metrics indicates the likelihood of collusion between the considered subjects. The resulting method for collusion discovery was tested with open data on the participation of legal entities in public procurement between 2015 and 2020 available at the federal portal https://zakupki.gov.ru. Quantum models are built for about 80 thousand unique pairs and 10 million unique triples of agents in the obtained dataset. The reliability of collusion discovery was defined by comparison with open data of Federal antimonopoly service available at https://br.fas.gov.ru. The achieved performance allows the discovery of about one-half of known pairwise collusions with a reliability of more than 50%, which is comparable with detection based on classical correlation and mutual information. For three-sided behavior, in contrast, the quantum model is practically the only available option since classical measures are typically limited to the bilateral case. Half of such collusions are detected with a reliability of 40%. The obtained results indicate the efficiency of the quantum-probabilistic approach to modeling economic behavior. The developed metrics can be used as informative features in analytic systems and algorithms of machine learning for this field.
Informatics and Automation. 2023;22(2):416-446
416-446
Position Correction Algorithm of Well Pads When Solving the Problem of Developing Oil Fields
Abstract
This article is devoted to the problem of automation of the stage of combining wells into clusters, considered as part of the process of designing the development of oil fields. The solution to the problem of combining wells into clusters is to determine the best location of well pads and the distribution of wells into clusters, in which the costs of developing and maintaining an oil field will be minimized, and the expected flow rate will be maximized. One of the currently used approaches to solving this problem is the use of optimization algorithms. At the same time, this task entails taking into account technological limitations when searching for the optimal option for the development of an oil field, justified, among other things, by the regulations in force in the industry, namely, the minimum and maximum allowable number of wells in a pad, as well as the minimum allowable distance between two well pads. The use of optimization algorithms does not always guarantee an optimal result, in which all specified constraints are met. Within the framework of this study, an algorithm is proposed that allows us to work out the resulting design solutions in order to eliminate the violated restrictions at the optimization stage. The algorithm consistently solves the following problems: violation of restrictions on the ultra-small and ultra-large number of wells in a pad; discrepancy between the number of pads with a given one; violation of the restriction of the ultra-close arrangement of pads. To study the effectiveness of the developed approach, a computational experiment was conducted on three generated synthetic oil fields with different geometries. As part of the experiment, the quality of the optimization method and the proposed algorithm, which is a raise to the optimization method, were compared. The comparison was carried out on different values of optimization power, which denotes the maximum number of runs of the target function. The evaluation of the quality of the work of the compared approaches is determined by the amount of the fine, which indicates the degree of violation of the values of the main restrictions. The efficiency criteria in this work are: the average value, the standard deviation, the median, and the minimum and maximum values of the penalty. Due to the use of this algorithm, the value of the penalty for the first and third oil fields is reduced on average to 0.04 and 0.03 respectively, and for the second oil field, the algorithm allowed to obtain design solutions without violating restrictions. Based on the results of the study, a conclusion was made regarding the effectiveness of the developed approach in solving the problem of oil field development.
Informatics and Automation. 2023;22(2):447-481
447-481