Blind adaptive detection using differential CMA for CDMA systems

In this paper, we consider the application of adaptive linear filters adjus ted by stochastic gradient algorithms to the suppression of multiple-access interference in DS/CDMA communications. It is pointed out that the linearl y constrained constant modulus algorithm (LCCMA) cannot converge to the opt imum point if the desired user magnitude is less than a critical value. Nex t, we propose to use the linearly constrained differential constant modulus algorithm (LCDCMA), and show that the LCDCMA always converges to the optim um point regardless of the desired user magnitude. Several simulation resul ts show the following three points. First, the LCDCMA provides better perfo rmance than existing algorithms because the variance of the weight vector a djusted by the LCDCMA is less than that by existing algorithms. Second, the LCDCMA is relatively insensitive to the estimation error of the desired si gnal vector. Third, the LCDCMA combined with a blind channel estimation alg orithm is useful. (C) 2001 Scripta Technica.