Development of a Radio Wave Propagation Model for Long-Haul Decameter-Band Communication Systems in the Decameter Range for the Analysis of Ionospheric Channel Parameters

Relevance. In long-haul decameter-band (LDB) communication systems, the number of bit errors is simultaneously influenced by two key factors: the signal-to-noise ratio and the degree of phase distortions caused by the Doppler shift, which arises from the random movement of ionospheric inhomogeneities. The challenge of improving the interference resistance of such systems is complicated by the fact that even with a high signal level at the demodulator's input, reception can be hindered by phase distortions, leading to a sharp increase in the number of bit errors and a degradation of the BER (bit error rate) coefficient. Despite the sufficient number of classical works, the problem of enhancing the interference resistance of modern domestic LDB radio communication systems under specified operating scenarios using contemporary methods and digital signal processing tools remains relevant and in demandich lead to a sharp increase in the number of bit errors and a deterioration in the BER coefficient. Despite a sufficient number of classical works, the problem of improving the noise immunity of modern domestic LDB or short-wave (HF) radio communication systems in specified operating scenarios using modern methods and means of digital signal processing (DSP) remains relevant and in demand. The object of the research is modern domestic decameter-band radio communication systems, which often exhibit known shortcomings, including low adaptability to changes in the ionosphere and issues with signal interference. For example, the R-016 system has limitations in its frequency range, making it less effective under varying ionospheric conditions that affect signal levels. Prototypes may also have problems with signal processing, which leads to bit errors of up to 10-3 even in the absence of noticeable interference. The subject of the study is the models and methods of functioning of LDB decameter-band communication lines.The objective of the research is to evaluate the impact of various factors, such as changes in preamble length and the use of adaptive filters, on the interference resistance of the system. The analysis of the obtained results shows that increasing the preamble length in such systems contributes to enhancing the interference resistance of long-haul communication. The scientific novelty lies in the improvement of existing radio propagation models in the decameter range by applying a complex of parameters that includes the signal-to-noise ratio set for a specific communication session in the radio line, and to increase the accuracy of field strength calculations at the receiving point, recalculated values of critical frequencies based on electron concentration forecasts, as well as Doppler shift for each layer of the ionosphere. The practical significance of the results lies in the enhancement of the interference resistance of existing decameter-band communication systems in ionospheric propagation conditions.

long-range communication system, signal-to-noise ratio, interference immunity, decameter radio communication, equalizer, preamble, adaptive filters