Performance of OFDM-CDMA System with Papr Reduction in Nonlinear Rayleigh Fading Channel

This paper studies an orthogonal frequency division multiplexing (OFDM) - code division multiple access (CDMA) system in the frequency-selective Rayleigh fading channel with the nonlinear distortion caused by high power amplifier (HPA). The bit error rate (BER) has been derived which agrees well with the simulation results. Next, we present a new technique to reduce the large instantaneous envelope variations of the OFDM-CDMA signals. This approach is a simple input-power management processing with just minimal extra bandwidth for side information. It is based on the recursive-least-squares (RLS) algorithm to minimize the mean squared error of input instantaneous power and the average input power to HPA, which is shown to suppress the peak-to-average power ratio (PAPR) significantly and improve the system performance as a result. Finally, from the spectral behavior investigation, the present power management is shown to yield a significant adjacent channel power ratio (ACPR) reduction.