A new SLM OFDM scheme with low complexity for PAPR reduction

The authors introduce a new selected mapping (SLM) orthogonal frequency division multiplexing (OFDM) scheme with low computational complexity. The proposed SLM scheme transforms an input symbol sequence into a set of OFDM signals by multiplying the phase sequences to the signal after a certain intermediate stage of inverse fast Fourier transform (IFFT). Then, the OFDM signal with the lowest peak-to-average power ratio (PAPR) is selected for transmission. The new SLM OFDM scheme reduces the computational complexity, while it shows almost the same performance of PAPR reduction as that of the conventional SLM OFDM scheme.

I. Introduction

An orthogonal frequency division multiplexing (OFDM) system has been proposed as a standard for the next-generation mobile radio communication system. OFDM signals have efficient spectral bandwidth, and the performance of the OFDM system over frequency-selective fading channels is better than that of the single carrier modulation system. One of the major drawbacks of OFDM system is that the OFDM signal can have high peak to average power ratio (PAPR). The high PAPR brings on signal distortion in the nonlinear region of high power amplifier (HPA), and the signal distortion induces the degradation of bit error rate (BER). Various techniques [1]–[6] have been proposed for reducing the PAPR. The simple and widely used method is clipping the signal to limit the PAPR below a threshold level, but it causes both in-band distortion and out-of-band radiation. Block coding [2], the encoding of an input data into a code word with low PAPR, is another well-known technique to reduce PAPR, but it incurs the rate decrease.