Improved concurrent constant modulus algorithm and soft decision directed algorithm based on fractionally spaced equalization

In digital communications, the constant modulus algorithm (CMA) for blind channel equalization has some disadvantages such as slow convergence speed and phase rotation. Therefore, an improved CMA+SDD (soft decision directed) algorithm based on FSE is proposed. The algorithm minimizes a modified error function and the learning-rate is modulated by the received sequences. The improved CMA+SDD blind equalizer is shown to have faster convergence speed, biggish improved steady-state equalization performance, and no phase rotation compared with the existing CMA blind equalizer.