The effect of nonlinear amplifiers on orthogonal-CDMA link and measures of performance, using a simplified amplifier model

Existing and forthcoming personal communication systems (PCS) like Globalstar, use orthogonal-CDMA (O-CDMA) modulation and solid state power amplifiers (PAs). These amplifiers are often operated near saturation to maximize user capacity. In this paper an ideal one carrier O-CDMA system and a simple cubic law PA are used to gain understanding on the performance degradation due to working near saturation of the PA. Three measures of performance are compared: noise power ratio (NPR), a suggested Walsh power ratio (WPR) measure and uncoded symbol error rate (SER). Results of all these measures, both analytical and numerical, are presented. It is concluded that WPR and SER are both acceptable, while NPR is too optimistic