Research On PAPR Reduction Of OFDM System In Wideband HF Communication

Orthogonal Frequency Division Multiplexing (OFDM) becomes one common technology in the high-speed communication owing to its robustness against multipath fading channel and high spectrum efficiency. However, an inherent drawback of OFDM signals is their high Peak-to-Average Power Ratio (PAPR). How to effectively reduce the PAPR of OFDM signal is an important issue. The problem is dealt with from two perspectives: firstly, the PAPR is reduced though carefully constructing the OFDM signal. Secondly, the linearity of HPA is enhanced by effective predistortion techniques.On one hand, techniques of reducing the PAPR are analyzed, such as clipping technique, coding technique and scrambling technique. Partial Transmit Sequence (PTS) and Pulse Shaping (PS) are studied in detail. Also, their performance of PAPR reduction, advantages and disadvantages have been analyzed. Compared to PTS, since there is no need of side information transmission, PS makes a better performance, especially in fading channels. On the other hand, the predistortion technique is considered to mitigate the problem. The analysis focuses on a digital adaptive predistortion method.The HPA estimator is designed based on the characteristic and it is easy to obtain the inverse of the rational bilinear function.A PAPR reduction scheme of OFDM system in wideband HF communication is proposed, which is based on the technique of Pulse Shaping and predistortion. MATLAB simulation shows that the scheme can work effectively in wideband HF communication system.