A PAPR reduction technique in OFDM transmissions using hierarchical QAM

摘要

Orthogonal Frequency Division Multiplexing (OFDM) is popularly used for high speed data transmission in various communication systems. However, an OFDM system has the main drawback of having high Peak to Average Power Ratio (PAPR) of the transmitted signals. High PAPR causes distortions in the signal when the signals that are modulated are passed through a high power amplifier (HPA). PAPR, if high, increases the hardware complexity and also brings down the power amplifier efficiency. Many techniques are practiced to reduce PAPR. In this article, a novel and effective technique of PAPR reduction is described in which Hierarchical Quadrature Amplitude Modulation (HQAM) scheme is employed. It is found that by increasing the ratio of distances between constellation points, PAPR can be reduced significantly.