Improvement and comparison of Modulus Algorithm Blind Equalizer learning curve in time and frequency domain

In this paper, we intent to realize the unknown channel and equalize the distorted signal simultaneously. Therefore, channel estimation is required in order to equalize the signal in the receiver side. However, the problem is that there is no information about the reference signal. Therefore, Blind Equalizer is suggested. Blind equalizers do not require any known training sequence for the startup period, but can rather perform at any time the equalization directly on the data stream. Moreover, due to utilization of Blind Equalizer, the pilot signal can be cut off so that the amount of transmitted data is reduced. Thus faster computational process is expected compare to conventional equalizer. In this paper, conventional method of equalization, Constant Modulus Equalizer, Modified Constant Modulus Equalizer and frequency domain process of Constant Modulus Equalizer and Modified Constant Modulus Equalizer are introduced, respectively. In order to evaluate the each scheme, we have analyzed with a simple multipath channel and calculated the Normalized Mean Square Error (NMSE). Also the computational complexity is evaluated for suggested schemes. Consequently, the Modified Constant Modulus Equalizer in time domain performed the lowest NMSE among given method. However, computational complexity point view of this paper, Frequency Domain Modified Constant Modulus Equalizer has the lowest complexity.