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• SIGNAL DEMODULATION USING CLASSICAL MACHINE LEARNING ALGORITHMS FOR THE WATTERSON MODEL

  А.S. Kirillov

  97-105

  2026-07-07

  Abstract ▼

  This paper investigates the application of classical machine learning algorithms for signal demodulation in a high-frequency communication channel described by the Watterson model. The relevance of this task stems from the need to improve noise immunity during broadband data transmission under conditions of multipath propagation and Doppler distortions. The classifiers used include Random Forest, Decision Tree, and k-nearest neighbors (KNN). The models are trained on synthesized data generated in the MATLAB Simulink environment, with varying path delays (0–4 ms) and Doppler shifts (0–10 Hz).
  The input features comprise the coordinates of signal constellations as well as the history of received symbols, since intersymbol interference significantly affects the position of the current point. The experiments revealed a critical feature: demodulation algorithms exhibit high sensitivity to variations in Doppler shift. A deviation of just 0.1 Hz from the training set parameters alters the structure of the signal constellation, increasing the bit error rate (BER) to 0.5. When the Doppler parameters align with the training grid, the Random Forest algorithm demonstrates the best performance, achieving a BER <0.01 on the full dataset. To address this sensitivity, a local training method with a reduced Doppler shift sampling step (down to 0.1 Hz) is proposed, enabling a BER ≤0.01 for Random Forest. Due to the exponential growth of the training dataset size (up to 1000 GB), data reduction techniques were developed: excluding time parameters and sampling data based on possible combinations of preceding bits. This reduced the data volume by a factor of 31.5 while maintaining a BER <10% for Random Forest with a training step of 0.2 Hz. The study concludes that the Random Forest classifier is suitable for demodulation in HF channels and highlights the necessity of adapting the training step to the required Doppler shift accuracy.

• INVESTIGATING MULTIPATH MESSAGE ROUTING ALGORITHMS THROUGH THREE-DIMENSIONAL GRAPH MODELS OF AUV NETWORKS

  N.V. Kolesov , А. М. Gruzlikov , Y.М. Skorodumov , V.S. Tiulnikov

  2026-04-29

  Abstract ▼

  This paper examines a class of telecommunication networks with mobile nodes, an important subclass within which is the so-called geography-aware networks. Their distinguishing feature is the availability of information about the geographic coordinates of all nodes in the network to each individual node, whereby each node is aware of the complete topology of the network graph, which enables rapid identification of the required number of information transmission routes between any two nodes. The purpose of this article is to investigate multipath routing algorithms. To this end, we propose a method for the automatic synthesis of adequate test models capable of representing networks of virtually unlimited complexity. The proposed solution is based on a compositional approach, in which a relatively simple network fragment that satisfies given constraints is first formed, and then the resulting model is constructed as a composition of copies of this fragment. To investigate the efficiency of multipath routing algorithms, we propose a compositional method for the random synthesis of test models of complex networks that satisfy constraints on distances between the vertices. This method was applied to the investigation of two routing algorithms, resulting in a large body of illustrative model data. The obtained results, presented in the form of graphs, demonstrate an increase in the gain in message transmission time as the queue length in the target flow grows. While the efficiency of multipath routing is insignificant under low network load conditions, its usefulness increases with growing network load. A similar increase in efficiency is demonstrated when transitioning from an algorithm that does not allow intersecting paths to an algorithm that allows such intersections.

• TRANSMITTING DATA IN 3D WIMAX CHANNEL BASED ON SISO-OFDM AND MIMO-OFDM

  V.P. Fedosov, Jaleel Sadoon Jameel, S.V. Kucheryavenko

  2021-02-13

  Abstract ▼

  This paper considers infrastructure to wireless mobile communications using Advanced-WiMAX. In this paper, the productivity performance throughput experienced the mobile users is compared in the cases of 3D SISO and 3D MIMO-channel models within a large urban cell. Re-cently, there has been substantial work and interest to expand MIMO and SISO-processing by taking into consideration in the design the elevation plane in addition to the azimuth dimension, Since the evaluation of elevation MIMO and SISO performance in 3D-channel design is needed. Bit-level simulation is performed for the channel in WiMAX operating at 2.5 GHz. The results indicate the accuracy of the 3D channel model, and the correct estimation of the 3D channel is showed. The difference in higher predicted capacity for the 3D channel model has resulted in the small-scale parameters for the SISO-case and the lower spatial correlation parameters for the MIMO-case. Different mobility speeds, the effect of the Doppler shift, several paths and the signal attenuation at a distance and with increasing frequency has been carried out in this study. Simulation runtimes are measured concerning the multi-section modulation types for both systems SISO and MIMO. Noise immunity is adversely affected by an increase in the number of spatial streams. The noise immunity is also affected by the increase in the number of antennas at the transmitters and receivers.

• THEORETICAL STUDY OF ESTIMATING THE PROBABILITY OF A CONNECTION IN SYSTEMS WITH BROADBAND SIGNALS AND FHSS

  D.I. Konkov , А. А. Schmidt , D.N. Polyakov , V.R. Bikbulatov

  285-294

  2025-07-24

  Abstract ▼

  The article is devoted to a theoretical study of the probabilistic characteristics of communication systems with broadband signals and pseudorandom tuning of the operating frequency in a complex electromagnetic environment. An analytical tool for calculating the communication probability is presented, taking into account the complex effects of multipath propagation, frequency-selective fading, and intentional interference. The dependence of the communication probability on the signal-to-noise ratio is investigated using integral expressions that take into account the normal power distribution at the input of the receiving device. A mathematical analysis of the transmission function of the communication channel as a complex characteristic describing the amplitude-frequency and phase distortions during signal propagation is performed. Theoretical models of synchronization processes are developed, including the stages of signal search, capture, and tracking, using the Markum function to describe the probability of signal detection against the background of Gaussian noise. Methods for optimizing the key parameters of the RFP system, such as the frequency tuning period, the total number of frequency channels, and the width of the protective frequency interval, are proposed. The theoretical foundations of adaptive control based on the maximum likelihood method and recursive filtering for estimating the parameters of the channel\are described. The energy efficiency of systems with RFP is studied, taking into account the frequency tuning losses and the necessary adjustment of the signal-to-noise ratio. A comprehensive indicator of the quality of a communication system combining probabilistic, energy, and time characteristics of the system is proposed. Analytical expressions are developed for estimating the intensity of synchronization failure based on statistical analysis of experimental data and calculation of the covariance matrix of measurement noise. The expediency of using reference signals to increase the reliability of measurements of communication channel parameters in adaptive control of the system is justified. Relations are derived for determining the duration of the synchronization window, taking into account the maximum allowable time of entering synchronism and the margin factor, which takes into account possible frequency instabilities of the reference generators.  The influence of the protective frequency interval on preventing inter-channel interference and ensuring electromagnetic compatibility of neighboring channels is analyzed. The presented theoretical results provide a scientific basis for the design of radio systems with increased noise immunity and can be used in the development of adaptive algorithms for controlling RF control systems in a dynamically changing electromagnetic environment, ensuring a balance between the reliability of information transmission and the efficiency of using frequency-time resources of the communication system.

• ADAPTIVE ALGORITHM FOR PROCESSING SPATIAL-TEMPORAL SIGNALS WITH REED-SOLOMON CODING FOR A THREE-DIMENSIONAL MODEL OF A WIRELESS RADIO COMMUNICATION CHANNEL

  V.P. Fedosov , Mohammedtaqi M. Jawad Al-Musawi Wisam , S.V. Kucheryavenko

  81-90

  2025-07-24

  Abstract ▼

  Reducing the probability of errors in message transmission is important in satellite, wireless and space communication systems. Reducing the probability of bit errors in a wireless communication system is possible by using encoding of the data being sent. Using channel encoding allows detecting and correcting errors in message transmission in a noisy channel. The aim of the work is to study the effect of using Reed-Solomon codes and the algorithm of space-time signal processing in a receiver using an adaptive antenna array on increasing noise immunity in wireless radio communication systems. In the presence of complex signal propagation paths, this allows performing spatial filtering in channels with reflections. The adaptation method, considered in this paper, is based on the theory of vectors and eigenvalues of the spatial correlation matrix. For Reed-Solomon codes, the simulation results show a significant decrease in bit error rates due to the correction of transmission errors. By using adaptive algorithms for single-input multiple-output orthogonal frequency division multiplexing (SIMO-OFDM) and multiple-input multiple-output MIMO-OFDM systems together with the Reed-Solomon code for the transmitted message, the signal-to-noise ratio for a fixed bit error level was increased to 8 dB and 5 dB, respectively. The results show that the adaptive algorithm with simultaneous use of the Reed-Solomon code can increase the throughput while significantly reducing the error probability. Under conditions of multipath signal propagation, it can be argued that the use of adaptive space-time algorithms improves the noise immunity of the receiving system during signal processing.