Efficient Blind Equalizer Schemes Using Variable Tap-length Algorithm

InterSymbol interference (ISI) distortion can be rectified without training sequence using blind equalization schemes. However, such a capability of the equalization methodology comes at the expense of high cost, and therefore it is necessary for the designers to think about efficient schemes to accomplish the blind equalization process. In this work, using a variable tap-length strategy, two algorithms for equalizing quadrature amplitude modulation (QAM) signals are proposed and tested. generalized Sato algorithm (GSA) and constant modulus algorithm (CMA) are incorporated with a variable tap-length technique to update the filter's coefficients and length. The variable tap-length method utilizes a fractional filter length in every iteration to optimize the filter coefficients and structure. Simulations are conducted in a microwave channel for 16-QAM, and the results have shown a considerable improvement in both mean square error (MSE) characteristics of the suggested algorithms as well as the ability of the presented algorithms to estimate the filters optimal length.