| OFDM can fight against multipath fading and time delay spread, meanwhile it own high rate of transmission and the spectrum efficiency. To the OFDM system using coherent reception is very important for estimation of channel. And good or bad of the performance can directly affect the performance of whole system. In this thesis, the technology of channel estimation in OFDM system that based on the pilot is analyzed and investigated.At first, the paper elaborates the development of technology of the OFDM system. On the basis of current technology of channel estimation in OFDM system, the thesis introduces the purpose and the meaning of the research. Meanwhile the property of wireless channel is analyzed. The thesis gives the model of OFDM system and elaborates the theory of system in detail.Then the thesis gives the process that direct towards the derivation and analysis of arithmetic of the channel estimation that based on the pilot. From the style of inserting the pilot, these arithmetic of the channel estimation about that based on block and comb pilot are researched in detail. Meanwhile the article gives the analysis and simulation of arithmetic.Finally, this thesis gives the proposal the mechanism between the performance of estimation and the efficiency of bandwidth,using controllable factor to control the performance of estimation and the efficiency of bandwidth. When the received signal in the training sequence and load the data co-exist in time. In the data detection,the training sequence and data carrying OFDM interference,resulting in a decline in system performance. So in some subcarrier for training sequence, the thesis use inserting zero to replace the data. Meanwhile this method can avoid the interference among data. So the arithmetic can improve the performance of estimation. Due to training sequence do not occupy the bandwidth of the system, while subcarrier for training sequence is data absolutely, the efficiency of bandwidth can be improved. |
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