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Transmission Systems Optimised spreading code redistribution PAPR reduction technique for 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 MC-CDMA systems can significantly degrade the power efficiency at the transmitter. This paper proposes an efficient PAPR reduction technique for the downlink of MC-CDMA systems. It regards the order of the CDMA spreading codes as an extra degree of freedom and exploits it to effectively reduce the PAPR of the signal. The proposed technique requires only slight modification to the MC-CDMA base station and negligible complexity to the mobile terminals. Both lightly loaded and fully loaded systems are examined when using the orthogonal sets of Walsh—Hadamard (WH) and Golay complementary sequences (CSs). It will be demonstrated that the proposed technique achieves significant PAPR reduction with low system complexity at both transmitter and receiver. Copyright © 2009 John Wiley & Sons, Ltd.