Research Of Reducing Peak-Average-Power Ratio Of OFDM System

High speed and reliability is required in future wireless data transmission system. With the rapid development of communication technology, broad and multimedia services is required to provided, which consist of data, voice, image, video and so on. People also require better communication quality and higher communication speed and larger capacity. So higher communication capacity and data transmission rate are becoming searching spot. OFDM (Orthogonal Frequency Division Multiplexing) can strongly combat multi—path fading and dispersive channel interference and keep high data transmission rate. Using DFT can greatly reduce the complexity of the receivers so OFDM is given more and more attention.However, many key problems of an OFDM system have not been solved yet, such as sensitivity of frequency offsets and high PAPR (Peak-To-Average Power Ratio), which limit wide application of OFDM technique .This thesis mainly focuses on the techniques of PAPR reduction and use MATLAB software to achieve simulation .We have achieved the following work:(1) This thesis first analyze the basic theory of OFDM signal and key technique . Then the paper introduces the orthogonal condition of sub-carrier.(2) This paper deduces the reason of high PAPR and sums up all kinds of methods of reducing PAPR all over the world. Then it analyzes the disadvantage of limited breadth filter and improve the companding method. Finally it uses MATLAB software to simulate the new method.(3) A coding scheme based on Golay Complementary sequences and Reed-Muller codes is proposed to reduce the PAPR.(4) SLM method and PTS method are particularly presented, and then put forward improvement based traditional SLM method. fn farther deep study about parameter and assistant adding power information this paper brings forward new method which may reduce the complexity of OFDM system. Last this thesis uses MATLAB software to simulate the new methods.