Vol 31, No 10 (2025)

The paper shows the dependence of the noise immunity of signals with multiple PSK and QAM modulation of a shortwave communication channel with Rician fading on the ratio of the operating frequency to the maximum usable frequency and the degree of ionosphere diffuseness. The noise immunity was estimated based on the moment function and numerical methods. Numerical calculations of the error probability were performed using the built-in MATLAB simulation tool. The values of the permissible signal-to-noise ratio were established to ensure the required error probability for PSK signals with a modulation ratio of M = 8 and QAM signals with a modulation ratio of M = 64. The modulation ratio of the signals was selected based on the signals actually used in the shortwave communication channel established in the MIL-STD-188-110B standard. Interoperability and Performance Standards for Data Modems. To estimate the signal fading depth in the Rician channel, a known technique for estimating the dependence of the Rician parameter on the ratio of the operating frequency to the maximum usable frequency and the degree of ionosphere diffuseness was used. Also, energy losses of the permissible signal-to-noise ratio of PSK-8 and QAM-64 signals were established in comparison with signals with binary orthogonal frequency modulation BFSK depending on the ratio of the operating frequency to the maximum usable frequency and the degree of ionosphere diffuseness. For QAM-64 signals, it was found that their energy loss relative to BFSK will be about 4 dB under normal diffuseness conditions and about 2 dB under moderate diffuseness conditions. For PSK-8 signals, it was found that their energy gain relative to BFSK will be about 4 dB under normal and moderate diffuseness conditions. The developed method allows, based on the results of probing the level of ionospheric diffuseness, to select such ratios of the operating frequency to the maximum usable frequency in a single-mode short-wave communication channel that will provide an acceptable value of the probability of erroneous reception of signals with multiple phase and quadrature-amplitude modulations. It is advisable to further develop this method to evaluate the throughput of a short-wave communication channel when receiving PSK and QAM signals with Rician fading.

The main object of this work is to automate the process of detection key words and phrases using modern natural language processing methods, which will improve the structure and classification of text data, as well as adapt them for further integration with classification systems. For this purpose, algorithm for automatic detection of key words and phrases from texts in Russian language is proposed for use in working with complex multi-level classification systems such as UDC, GRNTI. This algorithm can work with single texts without linking them to collections of documents. А joint frequency and morphological analysis was used to detect keywords and phrases, take into account the structure of the document. When detection of key phrases, lexical and grammatical patterns consists of adjectives and nouns were used as well as stable combinations of nouns. The algorithm effective works with large texts divided into segments (ones of relevant). To adjust the rank of a relevant text element calculated using frequency analysis. А special coefficient is introduced that depend on the areas of occurrence of keywords. The comparative analysis showed that, in comparison with the TF-IDF and TextRank algorithms, the developed algorithm demonstrates high efficiency in detection key words. The integration of the automatic text analysis algorithm with classification systems discovers an additional opportunities to structure knowledge and to improve process efficiency the large amounts of data.

The results of an experimental study of a program for technologically independent minimization of multilevel representations of systems of fully defined functions in the form of Boolean nets, which are based on Shannon expansions of systems of disjunctive normal forms (DNF) of Boolean functions, are described. The main attention is paid to the effectiveness of using the choice of the best (in terms of the number of literals of Boolean variables) function polarization option when minimizing of Boolean nets. Polarization refers to the choice of an inverse or conventional form of assignment of each of the system functions. For minimized polarized Boolean nets, logic circuits are synthesized in the design library of digital ASIC (Application-Specific Integrated Circuits). The obtained results are compared in terms of crystal area and speed (time delay) with the synthesis results for minimized unpolarized Boolean nets and for jointly and separately minimized Boolean nets built using polarized DNF systems.

The article suggests a method for embedding hidden data into the program dynamic memory. The method is based on connecting a dynamic authentication library. The library works directly with a heap of programs. The algorithm breaks the security label into blocks of the same size. The blocks are evenly distributed across the heap. The memory scheduler is not involved in the generation of this data. The method deletes embedded data after a certain time period. Heap address calculation parameters and time period are parameters of the algorithm. The authentication library that embeds the information is universal. The probabilistic model of the program with a heap is proposed in the article. This model is necessary to investigate the possibility of collisions between embedded data and dynamic program variables. The model treats the creation and deletion of dynamic variables as random events. Computer simulation of program behavior for different probability ratios was carried out. А computer experiment showed the basic patterns of heap use by the program. The simulation results demonstrate the linear dependence of heap filling on the probability ratio of creating and deleting variables. The criteria for selecting steganographic embedding parameters are determined based on modeling. The period for placement of embedded data blocks and the time of presence the steganographic insert in the program memory are determined by the statistical characteristics of the executable code.

The paper describes the method of increasing memory performance by reordering requests to memory controller. DDR SDRAM is organized in 8 or 16 banks. Each bank is independent from each other, but if the contiguous access requests go to the same bank, the old row in this bank precharge operation and activation of a new row operation have to be performed. If DDR SDRAM access has frequent open row conflicts in the banks, memory subsystem performance significantly decreases. To increase memory access bandwidth, we need to make data burst transfers as long as possible. However, for example, copying algorithms of the Debian Linux operation system use the burst length limited by the cacheline size. To avoid it, it is proposed to reorder read requests with write requests. The reordering control is being done with a state machine. This state machine delays write requests by a dedicated FIFO. Read requests are first processed. If the address dependence in the read and write requests is detected, those requests are sent to DDR SDRAM memory in order. After debugging on the simulator, this mechanism was implemented in a FPGA. The performance was measured on the data transfer cycles with and without requests reordering. Measurements on copying data using the Linux operating system show an increase in bandwidth up to 39 %.

The work is devoted to the method of structural-parametric synthesis of multivariant documents that can be used for automated preparation and modernization of families of documentation corresponding to families of equipment, software or other systems that are implemented by several modifications. To achieve the goal of the work, the method of vector optimization on a discrete set was used and a set of effect parameters for assessing the quality of a multivariant document was proposed. The practical significance of the proposed solution lies in the development of a method for synthesizing the structure and content of multivariant documents, the use of which allows reducing the number of characters in the documentation by more than 15 %, and also minimizes the labor intensity of its modernization, reduces the likelihood of errors in it and increases the ease of use.