Bit-Based SLM Schemes for PAPR Reduction in QAM Modulated OFDM Signals

In this paper, we propose two bit-based selected mapping (SLM) schemes for reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals with quadrature amplitude modulation (QAM), called bitwise SLM (BSLM) and partial bit inverted SLM (PBISLM). Contrary to the conventional SLM which rotates the phases of QAM symbols in the frequency domain, the proposed schemes change the magnitudes as well as the phases of QAM symbols by applying binary phase sequences to the binary data sequence before mapped to QAM symbols. Simulation results show that the proposed schemes have better PAPR reduction performance with shaping gain than the conventional SLM scheme for the QAM modulated OFDM signals, especially for the small number of subcarriers.

I. Introduction

Since orthogonal frequency division multiplexing (OFDM) can support high data rate and provide high reliability in voice, data, and multimedia communications, it has been adopted as a standard technique in many wireless communication systems. One of main advantages of OFDM is the robustness against frequency selective fading or narrowband interference. However, a critical drawback of OFDM is high peak to average power ratio (PAPR) which results in significant inter-modulation and undesirable out-of-band radiation when an OFDM signal passes through nonlinear devices such as high power amplifier (HPA) [1].