A Concatenated Equalizer/Trellis Decoder Architecture for a Terrestrial Digital Television Receiver

摘要

In the U.S. terrestrial digital television receiver, when the terrestrial channel presentsmultipath and additive white Gaussian noise, particularly strong multipath, errorpropagation in the feedback filter of a Decision Feedback Equalizer (DFE) severelyaffects the performance at the output of the trellis decoder. The performancedegradation occurs when incorrectly detected symbols are fed through the feedbackfilter. Then instead of mitigating Intersymbol Interference (ISI) from the cursorsymbol, the DFE enhances ISI. Error propagation causes bursts of decision errorsand a corresponding increase in the average probability of bit or symbol error. Thiswork evaluates the performance improvement achieved by a concatenatedequalizer/trellis decoder architecture for the receiver whereby the re-encoded trellisdecoder outputs are used as the input to the DFE feedback filter. In addition, theSoft Output Viterbi Algorithm (SOVA) is proposed for trellis decoding in order toachieve additional gains.