Comparison of Multiuser Detection Techniques for Asynchronous Multirate DS-CDMA Sysyems

Abstract:
This paper compares performance of various multiuser receiver structures for asynchronous multirate DS-CDMA systems over multipath Rayleigh fading channels. Bit-error-rates (BER) of the novel decorrelator based successive interference cancellation (DBSIC) detector and other commonly used suboptimum multiuser receivers such as the decorrelating, minimum mean-square-error (MMSE), SIC, parallel interference cancellation (PIC) and decorrelating decision-feedback (DF) detectors are evaluated for variable processing gain (VPG) CDMA systems with both perfect and imperfect channel side information. Simulation results show that DBSIC outperforms all other considered multiuser detection techniques in various multirate scenarios including cases with more than two rates at the expense of some additional complexity. The advantage of DBSIC is particularly demonstrated in the case where some physical users have increased data rates (i.e. heavier system’s load in terms of virtual users). It is also observed that, while all the receivers suffer degradation in performance in the case of imperfect channel estimates, DBSIC still outperforms the other detection schemes.