Low complexity concurrent constant modulus algorithm and soft decision directed scheme for blind equalisation

Abstract

The recently introduced concurrent constant modulus algorithm (CMA) and decision-directed (DD) scheme provides a state-of-art low-complexity blind equalization technique for high-order quadrature amplitude modulation (QAM) channels. At a small cost of slightly more than doubling the complexity of the standard CMA blind equalizer, this concurrent CMA and DD blind equalizer obtains a dramatical improvement in equalization performance over the CMA. In this paper, a new blind equalization scheme is proposed based on concurrent CMA and a novel soft decision-directed (SDD) adaptation. The proposed concurrent CMA and SDD blind equalizer has simpler computational requirements than the concurrent CMA and DD algorithm. Extensive simulation shows that it has the same steady-state equalization performance as the concurrent CMA and DD algorithm and a faster convergence speed over the latter scheme.