Dynamic Code-Allocation Based PAPR Reduction Technique for MC-CDMA Systems

Multicarrier code division multiple access (MC-CDMA/OFDM-CDMA) is a promising candidate for future high-data rate fourth generation (4G) wireless systems. However multicarrier modulation tends to have a high peak-to-average power ratio (PAPR) factor which leads to a significant degradation in the transmission power efficiency. In this paper we propose a PAPR reduction technique for the downlink MC-CDMA based on redistributing the spreading codes and optimizing the sequences with the objective to minimize the PAPR at the transmitter. Our technique utilizes the characteristic of the CDMA spreading codes as an extra degree of freedom that can be exploited to reduce the signal´s PAPR without any loss in the system performance. Both lightly loaded and fully loaded systems are considered with the orthogonal sets of Walsh-Hadamard and complementary Golay sequences. It will be shown that our proposed technique requires very low complexity and only a few side information, while at the same time achieves significant PAPR reduction.