Blind Equalization for QAM System in the Presence of Impulsive Noise

This paper investigates time domain-blind equalization of dispersive communication systems that employ high throughput quadrature amplitude modulation (QAM) signals under impulsive noise environments. A novel cost function that integrates negative moment with constant modulus algorithm is established to efficiently obtain the blind equalizer. Theoretical analysis indicates that the proposed negative moment algorithm (NMA) can effectively suppress the adverse effects of impulsive noise to improve the equalization quality. Also, a modified Newton method is designed to search for the optimal equalizer so that the blind equalizer can rapidly converge to the desired one. Moreover, the constructed iterative increment is proved to be the descent direction of the negative moment-based cost function, which guarantees the stable convergence of the proposed modified Newton method. In addition, computational complexity analysis of related methods indicates that the computational cost of the NMA is not significantly increased compared the least mean square methods. Finally, simulation results are conducted to show the good equalization quality and fast convergence speed of the proposed algorithm under impulsive noise environments.