Peak power reduction scheme based on subcarrier scrambling for MC-CDMA systems

We propose a new PAPR (Peak-to-Average Power Ratio) reduction scheme for MC-CDMA (multicarrier-CDMA) using subcarrier scrambling. Based on the fact that the PAPR of the MC-CDMA signal is highly dependent on the scrambling pattern of the subcarriers irrespective of users' data symbols, we searched the optimum fixed scrambling patterns for each combination of user spreading codes to achieve the minimum PAPR. This enables the system to dynamically allocate the optimum scrambling pattern during the system operation. The proposed scheme achieves a significant reduction in the PAPR compared to random scrambling, especially for a small number of users. We also propose a simple suboptimum scrambling scheme where a common scrambling pattern is used irrespective of the code combinations.