A hybrid nonlinear distortion compensator for multicode DS/CDMA systems

A multicode DS/CDMA is considered to be a promising technique for high rate data transmission, but it causes nonlinear distortion due to the multilevel amplitude characteristics after linear combining and nonlinear amplification at the mobile station (MS). This paper proposes a hybrid nonlinear distortion compensator that combines a predistorter at the MS and a maximum-likelihood (ML) detector at the base station, especially for the reverse link. The hybrid scheme can effectively compensate for the performance degradation due to nonlinear distortion by compromising the drawbacks incurred when either predistorter or ML detector is used separately. Simulation results show that the use of the hybrid scheme results in significant improvement compared to either one, and there exists trade-off between the two techniques in view of the back-off.