Spectrum Efficient DSI-Based OFDM PAPR Reduction by Subcarrier Group Modulation

Abstract

High peak-to-average power ratio (PAPR) is a long-standing problem of orthogonal frequency division multiplexing (OFDM) system. Although there have been a plethora of proposals presented to date, most of the proposals sacrifice spectral efficiency to attain low PAPR. In this paper, a concept of subcarrier group modulation (SGM) is proposed to transform those spectrum inefficient schemes into spectrum efficient ones. The SGM scheme groups available subcarriers, and assigns one extra bit to each group depending on one of two different sets of constellation, thereby freeing some subcarriers for PAPR reduction. At the receiver, the constellation set used in a particular group is determined by the maximum-likelihood detection. The SGM scheme can be integrated to different PAPR reduction schemes. In this paper, it is integrated with the dummy sequence insertion (DSI) scheme. The DSI with SGM can attain the same spectral efficiency as the conventional OFDM does. Through simulations, it is found that it can achieve PAPR almost similar to that the conventional DSI scheme does without degrading BER performance significantly over both additive white Gaussian noise and Rayleigh fading channels. In addition to the PAPR reduction application, the proposed scheme can be used to improve throughput of any conventional OFDM systems.