Combined-Step-Size Affine Projection Sign Algorithm for Robust Adaptive Filtering in Impulsive Interference Environments

This brief proposes a combined-step-size (CSS) affine projection sign algorithm (APSA) to improve the poor tracking capability of the conventional variable-step-size APSA. To achieve a good tracking capability, the variable mixing factor of the proposed CSS-APSA is investigated by using a modified sigmoidal activation function. Meanwhile, the variable mixing factor is indirectly updated by minimizing the L1-norm of the system error to ensure robustness in the presence of non-Gaussian impulsive interferences. The good performance of the proposed CSS-APSA is demonstrated in the system identification and echo cancellation scenarios that include the impulsive interferences.