Decision Feedback Equalizer With The Blind Matched Filter Estimation

Abstract

The optimal receiver front-end is the Matched Filter (MF) for a maximum Signal-to-Noise Ratio (SNR) in a communication channel with an Additive White Gaussian Noise (AWGN). The sampled MF output can be processed with the suboptimal yet computationally effective Decision Feedback Equalizer (DFE). In this paper, the filters of the DFE are derived in terms of the channel autocorrelation sequence which is estimated blindly using the sampled channel output signal. Initially, the MF followed by the DFE receiver the structure is operated in the Linear Equalizer (LE) mode (without the Decision Device (DD)) with the symbolrate sampled MF placed at the end of the receiver structure. During this LE mode, the MF is estimated blindly using the CMA. After the CMA converges, the structure is put back into its original form and the DD is included in the FeedBack Filter (FBF). The MF is adapted in the system identification structure using the detected symbols from the DD. In this way, the MF estimate from the CMA is improved further and an allblind DFE is realized for a Single Input Single Output (SISO) system. The Bit Error Rate (BER) values obtained from this structure are very close to those obtained with the true values of the MF and hence they proved that the structure is efficient and effective. 0-7803-8834-8/05/$20.00 ©2005 IEEE.

All-Adaptive Blind Matched Filtering for the Equalization and Identification of Multipath Channels—A Practical Approach

“…In Appendix B it is shown that as J gets larger, the very last coefficient of f F increases in value, while that of early filter coefficients get smaller and reach to zero. Since the first L components would be equal to zero, the filter in (30) can also be used as an alternative to (26).…”

“…However, once the matched filter is estimated so that the channel is, the channel estimate could be used to perform the Viterbi algorithm while the channel being updated in decision directed mode. See [26] for further reading on how the Viterbi algorithm can be used in the BMF receivers.…”