РАЗРАБОТКА АДАПТИВНОЙ СИСТЕМЫ СВЯЗИ НА ОСНОВЕ OFDM ДЛЯ ТРОПОСФЕРНОГО И РАДИОРЕЛЕЙНОГО КАНАЛА

Abstract

It is known that inter-symbol interference may occur during data transmission in radio relayand tropospheric communication systems. The presence of multipath propagation, frequencyselectivefading and extreme instability in the tropospheric and radio relay channel significantlyreduces the energy efficiency of the communication system. The aim of the work was to increasethe efficiency of using the channel for radio relay and tropospheric communication by usingOFDM (orthogonal frequency-division multiplexing) signals in the system using adaptive codingand modulation. In the course of execution, the modulator and demodulator models of the OFDMsignal are implemented. When using various signal code structures in various reception/transmission conditions, it is possible to achieve optimal use of the frequency and energyresources, to create systems that adapt to the conditions of signal propagation. To implement thismechanism, a service field was introduced into the transmitted service data, which contains informationabout the code rate used, the modulation type, and the interleaving depth. This approachallows optimizing the use of energy and frequency resources. Together with the use of channelquality estimation algorithms, it becomes possible to dynamically change the signal-code structurewhen the reception conditions change. By adjusting the interleaving depth, it is possible to optimizethe S/N threshold or the amount of information delay in the channel, depending on the systemrequirements. The use of adaptive choice of code rate and modulation will allow more efficient useof the channel resource with a constant change in its state. The obtained results will significantlyincrease the energy efficiency of the OFDM system, lead to stable communication in nonstationarychannels and increase the throughput.