A new approach for very low-PMEPR transmission in the downlink of a DS/CDMA system

We develop signal processing techniques for reducing the PMEPR (peak-to-mean envelope power ratio) for downlink transmission within CDMA systems. These techniques are compatible with conventional CDMA receivers, just requiring some modifications at the transmitter side. The proposed transmitter structure includes a nonlinear operation in the time-domain followed by a linear, frequency-domain filtering operation. To reduce the envelope fluctuation regrowth associated with the filtering operation, the clipping and filtering operations are repeated iteratively. We also include a semi-analytical statistical characterization of the transmitted signals, which takes advantage of the Gaussian-like nature of CDMA signals with a high number of users. This characterization is used in evaluating the performance of the proposed techniques. Our performance results show that we can reduce significantly the PMEPR of the transmitted signals, while maintaining the spectral occupation of the corresponding conventional CDMA signals.