Bidirectional decision feedback equalizer: infinite length results

The use of a decision feedback equalizer (DFE) that employs time-reversal of the received sequence in conjunction with a normal mode operation is considered for a packet transmission system. The bidirectional decision feedback equalizer (BiDFE) combines the output of the normal mode and time-reversal mode DFEs and is known to provide improved performance. This paper shows that, under the decision-error-free assumption, the BiDFE, with an infinite length MMSE-DFE in each stream, has a smaller performance penalty from the matched filter bound (MFB) when compared to each individual stream. The BiDFE tap coefficients are optimized to minimize the overall MSE and it is shown that the infinite length MMSE-BiDFE attains the MFB.