An improved technique to reduce peak to average power ratio in OFDM systems using gold/hadamard codes with selective mapping

Abstract

Despite its many advantages for high data rate transmission over frequency selective channels, one of the challenging issues faced by orthogonal frequency division multiplexing (OFDM) system is its high peak to average power ratio (PAPR). Selective mapping (SLM) is an efficient technique to reduce PAPR in OFDM without causing signal distortion. However SLM has high system complexity since it requires large number of inverse fast Fourier transform (IFFT) operations. And also it demands the transmission of side information for each data block which results in huge bandwidth overhead. In this paper, we propose an improved SLM technique with either Gold or Hadamard code which ensures low system complexity to achieve the same PAPR reduction performance as that of conventional SLM. Also the proposed SLM method promises superior PAPR reduction compared to that of conventional SLM for identical system complexities. Moreover, the proposed SLM approach needs less side information to be send to the receiver resulting in improved bandwidth efficiency. Simulation studies show that considerable reduction in PAPR than conventional SLM method is achieved for identical number of multiplying phase sequences. The effect of non-linear distortion caused by high PAPR is also studied and the proposed method is shown to ensure linear operation over a large dynamic range of high power amplifier (HPA) in an OFDM transmitter.