An efficient soft decision-directed algorithm for blind equalization of 4-QAM systems

Abstract

This paper introduces an efficient soft decision-directed algorithm (SDDA) for blind equalization of 4 quadrature amplitude modulation (4-QAM) systems. A novel cost function (CF) based on the conventional SDDA is established to efficiently obtain the weight vector of the blind equalizer (BE). An appropriately modified Newton method (MNM) which is proposed in our previous work [9] is adopted to fast search the optimal equalizer weight vector. It is shown that the BE based on the novel MNM has an approximately quadratic order of convergence like Newton methods. Moreover, the proposed algorithm has better stability and much lower computational load than Newton methods.