Research On Reducing Peak-to-Average Power Ratio Of OFDM Communication System

Orthogonal Frequency Division Multiplexing (OFDM) is regarded, as the key technology in the next generation mobile communication system for its high spectrum efficiency and robustness effective against multipath channel effect. OFDM has already been applied to many applications such as the DAB, DVB, HDTV, high-speed WLAN, HDSL, etc.However, one of the major drawbacks of this technology is the high peak-to-average power ratio (PAPR), which significantly restricts the practical application of OFDM. So, this thesis has done a lot of research that mainly focuses on the techniques of PAPR reduction. The main achievements of this work consist of following aspects::(1) This thesis firstly introduces the system model and basic theory of OFDM signal, and analyzes its advantages and disadvantages. And also it introduces the definition and distribution of PAPR in the OFDM system.(2) The paper makes detailed introduction and deep analysis on the most popular three kinds of PAPR reducing techniques, including pre-distorting technology, coding technology and non-distorting technology. Also, the paper makes corresponding performance simulation of the typical algorithm, and analysis of their respective advantages and shortcomings. Particularly, strong emphasis is cast on Clipping which belongs to the pre-distorting technology, and makes much research and simulation analysis of improved algorithm.(3) A simple and effective method that combines traditional clipping technique with LDPC code was proposed. Not only the traditional clipping technique could lower PAPR, but also it can improve the BER performance of the system and reduce the frequency dispersion by LDPC code combining with frequency-domain filtering. Matlab numerical results show that the proposed solution can reduce the PAPR effectively, improve the BER performance of the system and suppress the out-of-band radiation, which prove the effectiveness of this method.