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

A new PAPR (peak-to-average power ratio) reduction scheme is proposed 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, the optimum fixed scrambling patterns for each combination of user spreading codes are searched to achieve the minimum PAPR. This enables the system to dynamically allocate the optimum scrambling pattern during system operation. The proposed scheme achieves a significant reduction in PAPR compared to random scrambling, especially for a small number of users. A simple suboptimum scrambling scheme is also proposed where a common scrambling pattern is used irrespective of the code combinations.