A sign selection method of orthogonal variable spreading factor code for peak power reduction in multi-rate OFCDM systems

In this paper, we propose a novel peak-to-average power ratio (PAPR) reduction method for multi-rate orthogonal frequency division multiplexing (OFCDM) based on an orthogonal variable spreading factor (OVSF) code. In the method, the base station assigns two signs of code sequence to each user to maintain the orthogonality among the code sequences that have different lengths. After that, one sign of the code sequence is selected for reducing the PAPR of the OFCDM symbol. Based on theoretical analysis and computer simulation, we show that the proposed method reduces the PAPR for two data rate classes.