An Eight-parallel Hierarchical Constant Modulus Algorithm for Sixty-four Quadrature Amplitude Modulation

Abstract

One derivative type of the constant modulus algorithm (CMA) termed hierarchical CMA (HCMA) is investigated for its parallel implementation with 8 lanes. Taking the essence of CMA, HCMA is also the steepest descent under the least mean-square (LMS) criterion theoretically. To update the tap coefficients of the equalizer, HCMA utilizes adjustable modulus in accordance with the dynamical amplitude of the baseband signals. The above mechanism of HCMA can make the expectation of the error estimation converge to 0. The 8-parallel HCMA adopts the framework of the pipelined LMS adaptive filter. On the basis of the iterated short convolution and the relaxed look-ahead approximation, the implementation of 8-parallel HCMA can reduce much multiplication. The numerical simulation indicates that HCMA performs better than CMA with evident gain for the equalization of 64 quadrature amplitude modulation (QAM).