Integrating decision feedback equalization and forward error correction

Abstract

A method and system which combines a properly designed FEC and the periodic transmission of known symbols to obtain a desired error performance in a point-to-multipoint digital transmission system employing a DFE which induces error propagation. A transmitter unit includes a forward error correction encoder (FEC) which implements a code to information provided to an input of a data interleaver having block length N and interleaving depth D, and a data modulator which is coupled to an output of the data interleaver to receive a stream of data symbols. At least one receiver unit includes a decision feedback equalizer (DFE) which includes a feedback filter and provides an input to a data deinterleaver having block length N and interleaving depth D, and a FEC decoder which receives data from an output of the data deinterleaver. Sequences of known symbols of length at least equal to the length of the feedback filter are periodically added to the output of the data interleaver. The receiver unit uses knowledge of the sequence to pass correct data to the feedback filter. The number of data symbols between the periodic sequences is made equal to an integer multiple k of the interleaving Depth D, thus limiting error propagation to cause no more than k errors per codeward of block length N. The FEC code serves to correct the k errors per error propagation event.