Efficient Implementation of the Affine Projection Sign Algorithm

-norm optimization-based sign algorithms (SAs) are more robust against impulsive interference than -norm optimization-based adaptive filtering algorithms. However, most SAs suffer from slow convergence rate, especially for highly correlated input signals. In order to overcome this problem, recently, an affine projection SA (APSA) has been proposed , which exhibits fast convergence rate. In this letter, we first analyze the computational complexity of the APSA in detail and then apply a recursive approach proposed for the affine projection algorithm (APA) to the APSA to reduce its computational complexity. Analysis results show that the computational complexity of the APSA with the efficient implementation method is even lower than that of the classical fast affine projection (FAP) algorithm.