Optimized spreading code reallocation technique for PAPR reduction in MC-CDMA systems

Multicarrier code division multiple access (MC-CDMA) is one of the most promising techniques considered for future broadband mobile services. However, the high peak to average power ratio (PAPR) problem associated with multicarrier systems significantly degrades the power efficiency and makes it less preferred by the industry. In this paper, we exploit the order of the CDMA spreading codes as an extra degree of freedom to devise an efficient PAPR reduction scheme for the downlink of MC-CDMA systems. Both lightly loaded and fully loaded systems are considered when using the orthogonal sets of Walsh-Hadamard and Golay complementary sequences. The proposed technique requires only slight modification to the MC-CDMA base station and negligible complexity to the mobile terminals. It will be demonstrated that it achieves significant PAPR reduction with low system complexity at both transmitter and receiver.