System concept comparisons for multirate CDMA with multiuser detection

The decorrelating multiuser detector for asynchronous multirate multiuser code-division multiple-access (CDMA) systems is analyzed. A multirate CDMA system model able to fit several system concepts in the same framework is presented. The performance of the multi-code (MC) system with one processing gain and a multiple processing gain (MPG) system is compared. Lower bounds for the expected value of the asymptotic multiuser efficiency of a synchronous multirate CDMA system with three effective users are derived for a system with one and two processing gains. The numerical results show that the performance of the decorrelating detector for MC and MPG systems do not differ significantly.