Peak-to-Average Power Ratio Reduction Method Suitable for MC-CDMA System Downlink

In this paper, a novel peak-to-average power ratio (PAPR) reduction method named cyclic-shifted scramble code (CSSC) method is proposed for multicarrier CDMA (MC-CDMA) systems downlink. The proposed method utilizes the characteristics of multicarrier systems, i.e., if inverse fast Fourier transform (IFFT) input sequence changes, the output waveform also changes. In CSSC method, a scramble code assigned to a base station is applied to user data symbols after cyclic-shift. Comparing PAPRs of IFFT outputs amongst different shifts of the scramble code, the shift minimizing PAPR is selected and the MC-CDMA signal with the minimum PAPR will be transmitted. The receiver can estimate the amount of phase shifts by correlating between the scramble code and the received signal component in the pilot channel. The numerical results showed that PAPR can be reduced by approximately 3 dB by CSSC method without BER performance degradation