Design and Development of Hybrid Cos and Sine (CAS) precoding with reduced PAPR in OFDM system

Abstract

Reducing non-linear distortions by the HPA duty cycles away from their saturation region are not efficient in terms of power or cost. Another way to reduce these distortions would be to control the input signal of the non-linear amplifiers by lowering their PAPR as much as possible. By reducing the level of PAPR at the HPA input, its non-linear effects would be reduced. Since the margins of Input Back-Off (IBO) and Output Back-Off (OBO) would not saturate. Consequently, "back-off" levels could be reduced by improving the energy efficiency of the HPA. However, the main drawback of these techniques is the high computational cost they require. The majority of these PAPR reduction methods are applied before the IFFT block, where the signal in the frequency domain is modified so that the sum of the sinusoids in the time domain does not cause high peaks. However, there are techniques that act in the time domain, applied directly to these points. In this paper a hybrid CAS precoder method has been proposed. The partial transmit sequence method is used to reduce to PAPR of the proposed system. Simulations are carried out in MATLAB and performance of the proposed method is evaluated. By using the proposed CAS-PTS method,  50 % of PAPR is reduced compared with DCT based approach.