Equalizer with a sequence estimation method with state reduction for a receiver in a digital transmission system

Abstract

The invention relates to a digital transmission system having a receiver which includes an equalizer for estimating transmitted binary symbols, from a sequence of sample values (6) of a received signal distorted by a transmission channel, by a reduced-state sequence estimation method or a reduced-state single symbol estimation method (11). To provide a receiver featuring high reliability combined with a clear state reduction of the estimation method, a minimum-phase substitute system (14) distorts the sample values received after received after a known training sequence (27) in the sequence of sample values (6)in the received order, and a maximum-phase substitute system (14) distorts the sample values (6) received before a known training sequence (27) and to be processed in reverse order for forming an estimate (11) for a received signal. The number coefficients of the impulse response which are reduced by the state reduction and used for the estimation, render the estimation inaccurate. In a minimum-phase system, the first coefficients of the impulse response of the substitute system have maximum energy with an unchanged frequency response. When these coefficients transformed in this manner are used for the state reduction, nearly all of the information is used for the estimation. This achieves a high reliability of the sequence estimation as is achieved when all the states are used.

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