Decision Feedback Equalizer based Affine Projection and Normalized Least Mean Square Algorithms

In this paper, we address the problem of inter symbol interference (ISI) in digital communication channels by using adaptive equalization technique. The adopted structure is the decision feedback equalizer (DFE), combined with adaptive algorithms to eliminate ISI. In this paper, we combine the DFE based training sequence with the conventional affine projection (AP) algorithm, and compare it with the normalized least mean square algorithm (NLMS). This comparison is evaluated in terms of constellation diagram, and mean square error (MSE) criterion. The AP Algorithm based decision feedback equalizer technique have shown a faster convergence in comparison with DFE based on NLMS for the two types of modulation, 16-PSK and 16-QAM.