Analysis of BER Degradation for Transmitted Downlink DSCDMA Signals

A predistorter-high power amplifier (PDHPA) pair has become a common practice in wireless communication to compensate for nonlinear distortion due to HPA. However, the PD-HPA pair still produces severe signal distortion when the input signal exceeds the PD-HPA’s saturation level. The effects of such distortion on bit error rate (BER) degradation in downlink direct sequencecode division multiple access signals (DSCDMA) are analyzed. We establish which signal characteristics at the HPA input and the factors contributing to BER. Assuming that the baseband CDMA signal is characterized as a complex Gaussian process, we develop analytic expressions for the BER and the contributing factors to BER