On the performance of CDMA systems with nonlinear amplifier and AWGN

This paper proposes and discusses an analytical model for the evaluation of the effects of inband nonlinear distortion on the CDMA system performance. Both synchronous systems with orthogonal codes and asynchronous systems are considered. It is shown that in a broad range of cases, the nonlinear distortion in the decision variables at the receiver can be modeled by means of a complex scale factor and an additive noise, which is uncorrelated to the useful signal. Moreover, an analytical formulation of the bit error probability and total degradation (TD) as a function of output back-off (OBO) and number of user is given and the results are discussed for three classes of HPA models, the traveling wave tube amplifier (TWTA), the solid state power amplifier (SSPA) and the amplifier with ideal predistortion (IPA).