Compensation of nonlinear distortion with memory in multi-code CDMA systems

We present a predistorter to compensate for nonlinear distortion with memory introduced by linear pulse shaping filters and nonlinear high power amplifiers (HPAs) employed in multi-code code division multiple access (CDMA) systems. Since the multi-code CDMA system has multi-level properties in its signal amplitude, the performance of the system is significantly degraded by the nonlinear effect of the HPA in the transmitter. Furthermore, the memory of the linear filter employed in the multi-code CDMA transmitter generates intersymbol interference. In order to mitigate these distortions, we develop a new data predistorter, which rests upon the fixed point approach associated with the contraction mapping theorem. With utilization of the proposed predistorter, we can significantly improve the performance of the multi-code CDMA system compared to that of the system without the predistorter in terms of bit error rate