Research On OFDM Technique Used In High Speed Wireless Data Transmission

As the OFDM is more widely used in wireless communication increasely, in this thesis, the principle of the Orthogonal Frequency Divided Multiplex (OFDM) technique is studied, and the Peak-to-Average Power Ratio(PAPR) of OFDM is analyzed also. First of all, the OFDM is analyzed in detail;the basic model of OFDM system is given. The definition and character of probability statistics is researched, and the influence of oversampling on PAPR is described. Then the three main methods for reducing the PAPR of OFDM are summarized,included : signal distortion, scrambling, coding.According to the present condition of scrambling, in this thesis, the SLM for reducing the PAPR is researched and simulated, and the PTS for reducing the PAPR is analyzed and simulated also. Then the suboptimal PTS-OFDM algorithm is put forward, and the simulation results show that the CCDF performance is between the one when the most optimal method used and the one when no PTS used. From the duration of the program running process, it is concluded that although the complexity is heavily simplified, the system performance is just slightly deteriorated.Then, complement sequence coding to reduce PAPR value is discussed and simulated, as well as the specific coding&decoding ways being realized, the combined symbol rotation and Inversion method (CSRI) is researched ,and it is also simulated by using the tool MATLAB. And the result proved that CSRI is very useful to reduce PAPR of OFDM. Furthermore, the suboptimal combined symbol rotation and Inversion method (S-CSRI) is posed. The simulation shows that these two ways are of the capability of lowering PAPR sharply with slightly falling of performance.Compared to the PTS, CSRI cuts PAPR down more effectively. On the other hand, performing symbol cycle can reduce the value of PAPR more effectively than increasing phase weight coefficients, so CSRI is more suitable for being used in practice.