A.M. Saukov, S.I. Kovalyov, S.A. Dyoma, D.M. Krasyuk

High noise-immunity and efficient use of the radio-frequency spectrum have conditioned broad spreading of signals with orthogonal frequency division multiplexing (OFDM). The problem of estimation of their parameters during radiomonitoring of solved under conditions of a priori uncertainty and becomes more complicated in comparison with the earlier known radio signals . The traditional methods of separation and processing of some frequency channels do not allow to get the required results. The existing special facilities of radiomonitoring are oriented at documented standards and that is why they are not capable to process new types of OFDM signals the number of which to them all at present is more than 75 %. For eliminating the discrepancy of the requirements to special facilities of radiomonitoring as to their possibilities of automatic estimation of parameter of OFDM signals it is necessary to work out and introduce corresponding to approaches. The article deals with an advanced method of automatic estimation of the following most important parameters of OFDM signals: baud rate, carrying the frequencies, amount and frequencies of subcarriers, as well as the type of modulation on each of them. Its most important features are preliminary estimation and adjustment of the value of the frequency shift of subcarriers as to elementary frequency channels; use of non-standard functions for determination of duration of the interval of orthogonality on the basis correlative characteristics of the signal; estimation of location of positions and their number in the signal constellation on subcarriers with the use of the mathematical device of the cluster analysis. The use of this method, based on revealing structural regularities, allows to estimate the parameters and to demodulate OFDM signals of new undocumented standards. Correctness of the theoretical result received has been experimentally confirmed. It has been ascertained that the application of the worked out method for modernization existing facilities of radiomonitoring or the development of the new ones allows to enhance instrument accessibility of OFDM signal.