Adaptive blind MIMO channel estimation and multiuser detection in DS-CDMA systems

A novel adaptive blind approach is developed to simultaneously equalize and estimate the MIMO channel in DS-CDMA systems. The approach consists of two phases: multiuser detection and channel estimation. For multiuser detection, a blind adaptive space-time scheme developed in Kwak and Lu (1998) is employed to suppress the multiuser interference (MUI) or multiple access interference (MAI). The receiver consists of a space-time array and a decorrelator. The blind adaptive procedure is implemented using the constant modulus algorithm (CMA) and the decision directed algorithm (DDA). For channel estimation, the respread sequences of decision symbols are used as references. The MIMO (multi-input multi-output) channels are estimated (also blindly) using minimum mean square error estimation (MMSE). The adaptation to the varying environment or signals is implemented using the stochastic gradient method