A New Scheme For Reducing The PRPA Of OFDM System

OFDM is an efective data transmission technology thatd istributes the high-speed data over a large number of orthogonal carriers. It can be robust against multipath propagation and narrowband interference, and it also has a high spectral eficiency. Because of this advantages OFDM maybe become the key technology of the next generation of mobile communication. However, OFDM also has some drawbacks compared with single-carrier modulation, it is more sensitive to frequency ofset and phase noise and it has a relatively large peak-to-average power ratio(PAPR).The focus of zhis research is to resolve one of the main problems of OFDM system,higher Peak to Average Power Ratio(PAPR). This project is supported by the Nature Science Foundation of China under contact No.60372084.First of all, the paper introduces the basic theory of OFDM briefly and analyzes the probability characteristic of PAPR of OFDM system, and make a comparison among the methods to reduce PAPR in OFDM. After this, the paper introduces a new method which reduce the PAPR by utilizing the probability characteristic of PAPR: Firstly, it divides all subcarriers into several groups to reduce the subcarriers number of every IFFT ; and then the results multiply a specific matrix ,so every signal amplitude is replaced by the different average of many signals amplitude.In order to testify the feasibility and validity of this new method, the paper set up an OFDM system using simulation tools, MATLAB 7.0, and apply the new method in the OFDM system. The result proves the property of the new method without signal distortion and losing of bandwidth is better than the gived methods and can be applied in practice. In the end, the complexity and improvement of the new scheme is be reviewed.