OFDM系统频偏估计与补偿

his paper has recommended mobile communication development history at first, thus leading 3G mobile communication’s present development condition and its core technique- OFDM. This text mainly set up the basic principle and structures and advantages of the mold from the system, the parameter constitution of the system and the problem faced to elaborate the OFDM. Because OFDM is modulated of multiple carrier waves, the biggest problem faced is a synchronous problem. To resolve the frequency offset is the key to resolve the synchronous problem. So this text leans towards the reason produced from the system frequently offset and method emerging among the models, the method to produce Doppler frequency offset to explain. For carrier waves frequency offset which lead to interferences among sub carrier waves, usually adopt to estimate the frequency offset firstly and then carry on the frequency of the carrier waves to be corrected. This text mainly introduces two kinds of methods to estimate the frequency offset——Ask for help from the periodic delivering known sign to carry on the rectify of carrier waves frequency offset and Relevant estimations on the basis of the circulation prefix. Then make a comparison between the two methods. The method of frequency offset compensation adopted by this paper is a direct frequency offset compensation, namely frequency offset compensation before DFT, taking previous steps of frequency offset happened to estimate rotator angle make frequency offset for zero. Then explain mainly the modulation and demodulation of sub carrier waves under algorithms in ML, and compare the performance with carrying on QPSK modulation directly.