Methods for improving the energy characteristics of OFDM modems in frequency selective fading communication channels

T is a fact that during data transmission, inter-symbol interference can occur, caused by the presence of multipath propagation and frequency-selective fading in the radio channel, which can significantly reduce the energy efficiency of communication systems. One of the methods to combat such effects, relevant today, is the use of OFDM modulation (OFDM - Orthogonal Frequency Division Multiplexing), which allows to flexibly change the data rate, reduce the frequency resource by improving the spectral efficiency, and also deal with frequency - selective fading and selective interference. However, there are channels that are particularly susceptible to inter-symbol interference, such as, for example, the tropospheric channel. Also, the problem of selective interference is particularly acute in nearfield magnetic induction communication systems. For such channels, the use of OFDM modulation itself is not a panacea; the task of increasing the energy efficiency of an OFDM signal is an urgent one. This paper presents the key features of the OFDM mode of operation, which make it possible to increase the energy potential of the radio link in channels subject to intersymbol distortion. The results of modeling methods for PAPR reduction and digital predistortion for the linearization of the transmission path are presented. The practical significance of the work lies in the fact that the use of transmission path linearization methods will increase the maximum bandwidth of communication systems, primarily those using tropospheric, radio relay and near-field magnetic induction communication channels. At present, this issue is particularly acute, since there are no high-speed tropospheric stations with a data transfer rate of 50 Mbps in Russia. Increasing the throughput in tropospheric communication will provide communication to hard-to-reach settlements with difficult terrain. Also, the use of high-speed tropospheric communication is a costeffective alternative to satellite communication, since its use does not require the lease of a satellite channel.