Constant modulus algorithm for blind multiuser detection
Wookwon Lee, B.R. Vojcic, Raymond L. Pickholtz · 2002
We propose the use of the constant modulus algorithm (CMA) for blind adaptive interference suppression in code division multiple access (CDMA) systems. Synchronous multiple access signals are considered, for simplicity. The convergence behavior of the CMA is analyzed to examine the conditions for lock onto the desired signal. Since the multiple access interference dominates the performance, especially in severe near-far situations, we pursue the noiseless case to facilitate a simpler analysis. Two forms of the CMA update equations are considered. The first one is the standard gradient-descent based CMA. The second method, which we refer to as decorrelated CMA, employs the inverse of the channel correlation matrix to eliminate the effect of signals' cross-correlations on the convergence behavior of the CMA.