Low-complexity modified SLM method for PAPR reduction in OFDM systems

To overcome the multipath fading effect in wireless communications an efficient multicarrier modulation technique OFDM (Orthogonal frequency division multiplexing) is used. The OFDM system has high spectral efficiency and support high data rate wireless transmission without any additional requirement of equalization. So, it is an attractive technology formodern wireless communication systems. One major drawback of OFDM system is high peak-to-average power ratio (PAPR) of transmit signal. There are many methods to reduce PAPR in OFDM system, in which selected mapping (SLM) is one of the best distortion less method. However, it requires a bank of inverse Fast Fourier Transforms (IFFTs). Therefore, the system has more computational complexity. In this paper, we proposed a modified selected mapping (M-SLM) scheme using a perfect sequence /conversion vectors. In this method, the data sequences are equally divided then for the first half of the data sequence IFFT is taken then circular convolutionis performed with perfect sequences. conventional SLM is applied for the second half section to reduce the complexity and PAPR. Finally, the number of candidate signals are doubled from the same IFFT blocks. From the simulation results, the proposed method slightly reducesPAPR. Moreover, the computational complexity of the proposed method reduces much than C-SLM.

I. Introduction

OFDM (Orthogonal Frequency Division Multiplexing) is an efficient technique in which high data rate is achieved by dividing the available bandwidth into N number of narrow bands and then transmitting parallel [1]. With the OFDM principle many advantages are there, high spectral efficiency because of orthogonality among the sub carriers, robustness to channel fading, elimination of inter symbol interference, and converts the frequency selective fading into flat fading which reduces the equalizer complexity at the receiver side. The OFDM signals can be efficiently modulated and demodulated using inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) respectively because of these, it has already adopted as the standard transmission technique in the IEEE802.11a wireless LAN systems, digital audio broadcasting (DAB), and digital video broadcasting (DVB) [2]. For next generation mobile communication systems it is consider as one of the data transmission technique.