EVALUATION OF CHANNEL CODING EFFICIENCY IN OFDM TELECOMMUNICATIONS

The paper presents the results a study of methods for increasing the noise immunity of telecommunication channels with OFDM. The structure of the OFDM signal is investigated. The influence of the structure OFDM signals on the noise immunity of their transmission under the influence of the effect of intersymbol interference in a multipath channel is estimated. Recommendations are given on the choice of the OFDM signal form in order to counteract the influence of intersymbol interference by optimizing the duration of the pulse sequence. The behaviour of OFDM signals in the case of intersymbol interference in the AWGN and the Rayleigh channel is investigated. Recommendations for counteracting interference influence on the quality of communication are given. A comparison is made of the efficiency signal-code constructions based on concatenated codes in the case of their application in channels with OFDM. The article presents the results of the development models of effective coding in telecommunications with OFDM based on concatenated codes, taking into account the coding rate and the number of decoding iterations to ensure the specified noise immunity indicators. At the current stage of implementation of modern telecommunication technologies, the use of channel coding plays a key role in increasing the performance of channels that use OFDM. The main contribution of channel coding in combination with time and frequency interleaving is the formation of inter-bit communication in the data stream transmitted on separate carriers in the signal spectrum in such a way that the transmitted information data in the fading channel can be updated in the receiving equipment. In general, in this case, having frequency selectivity creates a certain advantage through frequency diversity. Thus, the presence of information about the state of the channel in the case of channel coding creates the prerequisites for obtaining a certain gain. Optimal in terms of speed and computational complexity, the selection of the scheme and algorithm for decoding the error-correcting code makes it possible to find a compromise in the design of concatenated circuits in channels with OFDM and ultimately obtain a satisfactory gain in performance.