Low PAPR mapping for 16-QAM OFDM-based systems

Orthogonal frequency-division multiplexing (OFDM) is widely being used in different wide band technologies. Due to the nature of OFDM, the transmitted OFDM symbol is the superposition of several orthogonal subcarriers. This generates a high peak-to-average power ratio (PAPR), which degrades the overall system performance. In this manuscript, a new mapping scheme for 16-QAM that reduces the PAPR of the OFDM symbol is presented. Our proposal is based on reducing the amplitude of the symbols within the edges of the constellation. The new 16-QAM mapping is characterized by a lower PAPR, but with a small increase in terms of the bit error rate (BER). In terms of throughput, the proposed mapping scheme keeps basically the same trend as the traditional 16-QAM mapping scheme.

I. Introduction

ORTHOGONAL frequency-division multiplexing (OFDM) based systems have found widespread use in wireless technologies such as Wireless MAN (WiMAX) and Long Term Evolution (LTE), due to its high spectral efficiency and robustness in multipath environments [1]. However, it has the drawback of a high peak-to-average power ratio (PAPR), which generates a negative impact in its applications [2], [1]. To reduce the problems resulting from high PAPR, amplifiers must operate in back-off operation. This affects the power efficiency of the amplifier negatively. Considering this, the reduction of PAPR is a fundamental task in OFDM [3].