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A study on the PAPR using variable code sets (VCS) in multi-user MC-CDMA system

Because an MC-CDMA system raises the high peak-to-average power ratio (PAPR), it has some disadvantages, such as nonlinear distortion at a high power amplifier (HPA), a significant power efficiency penalty and the degradation of the bit error rate (BER). Various methods for reducing PAPR have been proposed for the MC-CDMA system, such as partial transmit sequence (PTS), selected mapping (SLM), etc. However, these schemes require some side information bits which result in some losses of transmission efficiency. We do not use any side information bits. We decide a threshold to combine all of the code sets. The code set which exceeds the threshold is fed back. As a result, the transmitted symbols have a PAPR less than that required of the system. The basic idea of the proposed scheme is to generate a signal based on variable code sets (VCS), and to choose, before the transmission, the signal which has a smaller PAPR than the threshold.