The Research On The Algorithm Of Reducing Thd Peak-to-Average Ration And Carrier Wave Synchronization In The OFDM System

With the development of the communication technology, people have entered the wireless communication age. In many communication technologies, the orthogonal frequency division multiplexing (OFDM) technology with its excellent transmission advantage has become the core technology of wireless communication.According to the principles and characteristics of the OFDM wireless transmission system, the reducing Peak-to-Average Power Ratio about this system is researched in this thesis. In order to improve the transmission performance of the system effectively, three methods are analyzed, including clipping method, U-rate(μ rate) Logarithmic method and the piecewise linear method. To get the applicable transmission environment of each method and improve the transmission performance of the system, the mathematical model of simulation comparison with MATLAB is given. Because the OFDM system is sensitive to the carriersynchronization migration, the problems of the integer times and decimal times thick and fine carrier frequency synchronization are discussed. Key points of each synchronization problem are analyzed and a new synchronization algorithm is introduced in this thesis. For integer times synchronization, FFT sliding windows are ensured and synchronous effect is improved through the addition of the adjacent frequency phase. The new algorithm of decimal times thick synchronization is carrying on the conjugate operation to the neighboring two protection intervals and gets the carrier wave frequency offset; the new algorithm of decimal times fine synchronization is using carrier samplings to get the pilot frequency and to calculate the carrier wave frequency offset. Finally through MATLAB simulation and comparison, the conclusion is that the new synchronous algorithm is of good performance.