A Low Complexity PAR Reduction Technique Using Cyclic Shifted Data Sequences in DS-CDMA Signals

Downlink direct sequence-code division multiple access signals have a large dynamic range causing these signals to be distorted by the nonlinear characteristics of the high power amplifier. The signal dynamic range is often characterized by peak-to-average ratio (PAR). Several techniques have been proposed to minimize such forms of distortion by reducing PAR such as partial transmit sequences and selected mapping (SLM), where several representations of the same signal are generated and the one with the minimum PAR is selected for transmission. Such techniques remarkably improve the system performance, but at the expense of an increased system complexity and computational burden. In this paper, we present a low complexity technique to reduce PAR based on cyclic shifts of the users´ data sequences (namely CSS). The search and optimization procedure in the proposed CSS technique is also simplified by adopting a greedy algorithm that selects the best representation sequentially as new users are added to the system. Comparison of the presented technique against SLM shows comparable improvement in terms of PAR reduction and bit error performance but with remarkable complexity reduction.