Design criteria for phase sequences in selected mapping

Multicarrier code division multiple access (MC-CDMA) has attracted much attention to the fourth generation mobile communication systems, because it can realize high-bit-rate and high capacity transmission by multiplexing information symbols of many users with orthogonal codes. One disadvantage of multicarrier modulation is its high peak-to-average power ratio (PAPR) that results in nonlinear distortion at a high power amplifier (HPA) and the degradation of the bit error rate (BER). Various methods have been proposed for reducing PAPR. Among them, partial transmit sequences (PTS) and selected mapping (SLM) have been investigated intensively. PTS and SLM have been applied to MC-CDMA. We showed that SLM is more effective than PTS at the same amount of side information. We also showed that the random sequences can reduce the PAPR most as phase sequences in SLM by computer simulation. However, it has not been clarified why the random sequences are good as phase sequences in SLM and how we should design phase sequences in SLM. In this paper, we propose design criteria for phase sequences in SLM.