Методология и макет программно-конфигурируемой сиcтемы для низкоскоростной передачи информации по ионосферному радиоканалу с высокой надёжностью
Authors: Иванов Д.В. , Иванов В.А. , Елсуков А.А. , Рябова Н.В. 
Published: February 2025

Разработана методология низкоскоростной передачи информации по ионосферному радиоканалу при одновременном получении информации о его состоянии в результате использования сложного сигнала типа FMCW–FSK. Рассмотрены вопросы выбора параметров такого сигнала с учётом совмещения системы сенсорной диагностики ионосферного радиоканала и передачи информации. Разработан реализующий данную методологию макет программно-конфигурируемой радиосистемы передачи информации и проведена его апробация в лабораторных экспериментах при имитации ионосферного радиоканала многоотводной линией задержки.

Introduction. For high-rate and reliable data transmission over the ionospheric channel, selecting the most appropriate operating frequency is crucial, which is achieved through spectral monitoring methods and sensor diagnostics across the entire frequency range. However, for scenarios involving small data volumes, employing a low-rate transmission mode alongside sensor diagnostics is reasonable. In this mode, a brief telegraph message is repetitively transmitted over all available frequencies, increasing the likelihood of finding the optimal frequency for transmission. Enhancing the dependability of message delivery over extremely long distances through HF communication systems represents a challenging scientific objective. It demands further research and the development of methods, algorithms, and hardware solutions to enable highly reliable, low-rate, and small-data volume transmission over ionospheric radio channels using spread spectrum signals. The aim of this research is to develop and experimentally validate a methodology and layout for sensor diagnostics and low-rate data transmission over an ionospheric radio channel, enhancing its reliability. Research methodology.To achieve low-rate data transmission across an ionospheric radio channel, we tackled the challenge of integrating Frequency-Modulated Continuous Wave (FMCW) diagnostic signals with Frequency-Shift Keying (FSK) communication. Signal parameters were chosen considering the peculiarities of processing echo signals for Near Vertical Incidence Skywave (NVIS) radio links. This methodology was then realized on a software-defined platform, USRP-N210, for low-rate data transfer. The methodology and prototype underwent testing in a laboratory experiment. We employed a multi-tap delay line and an adder to simulate a communication channel. The delay line enabled us to replicate various propagation modes and the bandwidth characteristics of the ionospheric radio channel. Findings. Following the experiment, we successfully obtained frequency-dependent power delay profiles for the simulated radio channel and the test telegraph message simultaneously. Our analysis of the results reveals that this method ensures reliable message transmission, even in cases where certain frequency ranges exhibit a high error rate within the channel's transparency band. We shall note, that 39% of the messages were received error-free, corresponding to the transparency band. Furthermore, in diagnostic mode, we can effectively identify the tracks of frequency-dependent signals reflected from the ionosphere, determining both the delay and energy losses. Conclusions. The results we've obtained have practical applications in the development of advanced HF communication systems designed for transmitting concise telegraph messages with exceptionally high reliability over extensive distances. These systems are crucial for sending control commands, brief emergency messages, and telemetry data in regions with limited or no continuous coverage by information and communication networks.