The Research On Reducing The OFDM's Peak-to-Average Power Based On Discrete Cosine Transform

In the use of mobile communication, Orthogonal Frequency Division Multiplexing (OFDM) technology has many advantages, such as transmiting high-rate data, high spectral efficiency, combating ISI (Inter-Symbols Interference) and multi-path delay, etc. However, this system has some disadvantages itself, for example, sensitivity of frequency offset and high PAPR (Peak-to-Average Power Ratio). These problems of an OFDM system must be solved in practical application.This paper focuses on the research of the PAPR problem of OFDM system. The high PAPR is a major bottleneck problem due to limiting OFDM system's practical applying. What's more, the high PAPR can result in cross-modulation-distortion for OFDM signal and decline the system performance. Firstly, the key technology and advantages/disadvantages of OFDM system based on DFT( Discrete Flourier Transmission) are argued in this thesis,The definition and distribution of PAPR are given and methods of reducing PAPR home and abroad are summarized. The complete analysis and compare are done aiming at SLM (Selective Method) and PTS (Partial Transmission Sequences) of signal interference technology. Secondly, a new method applying DCT (Discrete Cosine Transmission) to reduce PAPR of OFDM signal is proposed in this paper. Furthermore, this paper discusses the PAPR performance during the different conditions. At the same time, the results of the system simulations based on the MATLAB show that DCT can reduce PAPR effectively and improve the OFDM systems' PAPR performance. Finally, the frequency specifications and noise performance of OFDM signal based on the DCT method are argued. And the technology characteristic of the DCT method proposed in this paper is summarized.