Fractionally sampled linear detectors for DS-CDMA

In this paper we analyze the performance of fractionally chip sampled linear multi-user detectors for Direct-Sequence CDMA communication systems. We consider a general DS-CDMA system model accounting for user asynchronism and frequency selective propagation channels. Analysis shows that FIR linear defectors with chip rate sampling cannot perfectly recover N or more users for a system with spreading gain N in the presence of frequency selective channel dynamics or user asynchronism. Drawing inspiration from fractionally spaced equalization, we propose the fractionally chip sampled receiver and show that a FIR linear detector may be able to perfectly recover greater than or equal to N users.