Spreading code sharing MPSK-MC-CDMA system for low PAPR in wireless communications

We introduce a spreading code sharing M-ary PSK multicarrier CDMA (SCS-MPSK-MC-CDMA) system to obtain low peak-to-average-power ratio (PAPR) level in MC-CDMA system. The main advantage of the system is that low PAPR values can be obtained with a large system capacity. However, BER performance is similar to the conventional M-ary PSK MC-CDMA system. The PAPR reduction method of low PAPR spreading code selection (see Thilak Ginige et al., WPMC´00, vol.1., p.39-44, 2000) can be applied with the 4-QAM-OFDM-CDMA system as well as SCS-MPSK-MC-CDMA systems. It can be shown that, by applying this technique, the 15 dB PAPR level of a 90 user conventional MPSK-MC-CDMA system with 128 Walsh Hadamard (WH) code can be reduced to 13 dB by employing 64 WH codes with the same capacity and data rate. The dynamic spreading code allocation technique (see Thilak Ginige et al., IEEE Commun. Letters, p.408-10, 2001) also can be applied in SCS-MPSK-MC-CDMA system to reduce PAPR level further. Since MPSK systems are extremely sensitive to phase errors, the proposed SCS-MPSK-MC-CDMA system can be applied to indoor wireless systems with a larger number of users.