Abstract
This article examines the current state of the science of the causes of digital signal distortion. Cellular and radio relay communications, data transmission over computer networks, digital radio broadcasting and television, presented in various and diverse formats, covered all countries of the world. The high quality of communication, relatively low costs for its organization and, therefore, accessibility to the general population of all countries, ensured this success. Modern digital communication systems use all the mastered frequency ranges, different types of modulation and signal processing methods. A real wireless communication channel has time-frequency scattering, which leads to inter-character (MSI) and inter-channel (MCI) interference. By itself, this phenomenon does not lead to big problems, because there are quite a lot of effective methods of fighting. At the present stage, for channels with time-frequency scattering, multiplexing (compaction) with orthogonal frequency division (OFDM - Orthogonal Frequency Devision Multiplexing) is considered the best. The article presents methods of combating distortion, noise-resistant channel coding, the use of OFDM, FBMC, UFMC.