In recent past there has been an ever increasing demand in the capacity which is either due to increase in the number of subscribers, or high data rate requirement of multimedia and wireless internet services. Therefore wideband code division multiple access (WCDMA) has gained tremendous attention. The multiuser detectors (MUD) for these systems are major research issue. However, the capacity, and hence the data rate of wireless communication are limited due to the obvious reasons of frequency selectivity and time varying nature of the multi-path wireless channel. The other formidable limiting factors for the capacity of the wireless system, especially when the system becomes overloaded, are MAI and computational complexity of MUD. The solution to these limiting factors is the main focus of this book.