Linear FIR multiuser detection for multiple data rate CDMA systems

Ideal linear multiuser detectors for code-division multiple-access (CDMA) systems have infinite memory-length (referred to as IIR detectors). To obtain practical detectors for CDMA systems linear finite memory-length (referred to as FIR) multiuser detectors have been proposed. We generalize the linear FIR detection to CDMA systems supporting multiple data rates. A generic multirate CDMA system model is formulated, which can represent different multirate system concepts. We analyze the performance of the FIR decorrelating detectors in multiple processing gain CDMA system and present several numerical examples. It is demonstrated that a moderate memory-length FIR decorrelator provides the performance of an IIR decorrelator, which makes decorrelation feasible in practical multirate CDMA systems.