"The Spectral Approach to Adaptive Signal Filtering under Intersymbol Interference"

"To combat intersymbol interference caused by multipath propagation of radio waves, an adaptive filter is proposed. It is assumed that there are no linear distortions in the information transmission channel. A guard time interval exists between transmitted channel symbols. The duration of the guard interval is chosen such that an interfering channel symbol with the maximum delay time does not affect the preceding or fol-lowing channel symbols. The number of interfering symbols is assumed to be known. To adapt the filter, the attenuation coefficients and delay times of the received channel symbol and its delayed copies are determined. Systems of equations for determining the desired quantities are constructed based on the spectral representation of the received mixture. Three methods for constructing such a system of equations are proposed. It is shown that additive channel noise affects the accuracy of determining the desired quantities. It is hypothesized that the level of this influence also depends on the method for determining the desired quantities. A block diagram of the adaptive filter is provided."