Variable step size dual mode blind equalization algorithm based on forgetting factor

Constant mode blind equalization algorithm has been widely used in wireless communication system, but it has the problem of excessive steady-state error, so it usually adopts the combination of constant mode algorithm and decision guided least mean square algorithm. The traditional double mode blind equalization algorithm adopts the idea of weighted combination or switching, and the weighted combination method is complicated and impractical. The dual mode switching completes the algorithm switching by setting the threshold value, but the rationality of the switching time cannot be guaranteed. In this paper, a kind of mean square error estimator is constructed by using forgetting factor as the condition of algorithm switching, which ensures the rationality of switching time. In the convergence stage, modified constant modulus algorithm is used, and after convergence, decision guided least mean square algorithm is switched, and introducing the Softsign function to control the step size to improve the convergence speed of the algorithm. The simulation results indicate that the new algorithm has better steady state error and convergence speed, it also reduces the bit error rate.