A Fuzzy Approach For Semi-Blind Equalizer Design

In wireless communication, the semi-blind equaliztion and blind equalization is a very important issue. Through the distorted and multipath channel, the received signals were interfered by the channel and the bit error rate (SNR) is high. So the equalizer is usually used to equalize the intersymbol interference. In the conventional zero-forcing or minimum MSE equalizers, a known training sequence is transmitted to the receiver for purpose of initially adjusted the equalizer coefficients. However, there are some applications, such as multipoint communication networks and multiuser communication, it is desirable for the receiver to synchronize to the received signal and to adjust the equalizer without having a known training sequence available. Equaliztion techniques based in initial adjustment of the coefficients without the benefit of a training sequence are said to be self-recovering or blind. One of this technique is called semi-equalization. In the semi-blind equalizer, the parameters is initialled by the knowledge of some known symbols from dedicated training or perhaps from synchronization overhead. Then the parameters of the semi-blind can be adjust by some algorithm.In this paper, a fuzzy approach to semi-blind equalization of nonlinear and finite-duration response (FIR) channels is proposed based on recursive least-squares (RLS) and the constant modulus algorithm (CMA). The new approach which merged the characteristic properties of fuzzy system has a high accuracy and fast convergence rate in comparison with usual algorithms. Simulations also show the superior performance in binary phase shift keying (BPSK).