Hybrid DFE with variable length feedback filter

In the paper, a hybrid decision feedback equaliser (DFE) with a feedback filter (FBF) whose length can be dynamically adjusted is presented and investigated. The equaliser is an adaptive DFE with a feedforward filter (FFF) implemented in the frequency domain with its length fixed by the FFT/IFFT size and a feedback filter (FBF) in the time domain. The FBF length is adjusted according to the achieved mean squared error (MSE). In addition, the impact of small FBF coefficients on system BER performance is taken into account so that a shorter filter length can be considered. Computer simulations show that the proposed approach is capable of adjusting the feedback filter length to a satisfactory level in terms of MSE and system BER performance and is able to track channel changes successfully.