Research On The Methods Of Channel Estimation In OFDM Communication Systems

As a high-speed multi-carrier transmission technology, OFDM has been regarded as the core technology of next-generation mobile communication systems due to its high bandwidth efficiency and robustness combat interference ability. Channel estimation, as the key technology of OFDM systems, has become a hot issue that people study.The channel estimation method based on pilot is studied in the thesis. To block-type pilot arrangements, the least squares estimation algorithm and the minimum mean square error estimation algorithm are discussed. To comb-type pilot arrangements, the methods of constant interpolation, linear interpolation, second-order interpolation, spline interpolation and time-domain interpolation are discussed. According to the distribution character of wireless channel response, the channel estimation method based on DFT noise suppression by time-domain filtering is proposed, and this method has been improved; at the same time, the channel estimation method based on DFT noise suppression by transform domain filtering is proposed. Experimental results show that the channel estimation method based on DFT noise suppression can eliminate most of noise, at the same time, most of channel energy is reserved. This method can reduce influence of noise on systems performance, improve accuracy of channel estimation. In addition, the channel estimation method based on decision feedback is studied in the thesis. To the defect that decision feedback method has a lot of incorrect decision, the forward error correction coding technique and the decision feedback method are combined in the thesis, and the coding feedback channel estimation method is proposed. Experimental results show that the coding feedback channel estimation method can combat multi-path fading and Doppler frequency shift effectively, with good performance in the complex channel environment.