Fast blind equalization with two-stage single/multilevel modulus and DD algorithm for high order QAM cable systems

In this paper, a fast blind equalization with two-stage single/multilevel modulus and decision-directed (DD) algorithm is proposed for high-order QAM (256/1024QAM) systems on the downstream wired cable channel. The proposed blind equalization algorithm applies the two-stage convergence scheme, which results from the modified constant modulus algorithm (MCMA) method and the DD least mean square (LMS)-like method. In the first convergence stage, the joint MCMA and DD LMS-like equalization is applied for the purpose of fast convergence. When the convergence process reaches the enough steady state, the convergence detector will switch the equalization process into the second stage. In the second convergence stage, the MCMA with multiple modulus, called the generalized MCMA (GMCMA) method and the DD LMS-like method, is applied to reduce the mean square error (MSE) further. On the cable channel with the 256/1024QAM schemes, the proposed algorithm performs faster convergence speed than the previous well-know blind methods do. Simultaneously, the proposed algorithm also provides better MSE performance than the other methods at the same signal-to-noise ratio (SNR).