Performance of VSG-CDMA and MC-CDMA in multirate systems
Zihua Guo, Khaled B. Letaief · 2002
The performance of two multirate schemes in DS/CDMA systems, variable spreading gain (VSG-CDMA) and multicode (MC-CDMA) are compared. We first present the signal model for a multirate DS/CDMA system. Then, the performance in terms of asymptotic multiuser efficiency (AME), near-far resistance (NFR), and BER are evaluated. Some typical detectors are considered in multirate systems. These include the optimal maximum-likelihood detector, the sub-optimal linear detector, the interference canceller and the conventional MF detector. We show that in multirate systems, MC-CDMA has a very similar performance to VSG-CDMA employing low-rate detection (LRD). But it performs much better than VSG-CDMA employing high-rate detection (HRD). Furthermore, we show some important distinctions between multirate systems and single-rate systems.