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Channel Estimation Based on FFT and Improvedalgorithm for OFDM Systems

Author: LiuHui
Tutor: YangJinSheng
School: Tianjin University
Course: Communication and Information System
Keywords: Orthogonal Frequency Division Multiplexing COST 207 Channel FFT Interpolation Adaptive Channel Estimation
CLC: TN919.3
Type: Master's thesis
Year: 2010
Downloads: 94
Quote: 0
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Abstract


With the rapid development of digital communications in recent years , the demand for high data transmission technology, with the Japanese surge . Orthogonal frequency division multiplexing (OFDM) technology in the wireless environment , a high data rate transmission and resistant to inter-symbol interference , so more and more people's attention . OFDM as one of the key technologies for the next generation of wireless communication systems . In the OFDM system , usually the coherent demodulation, the differential demodulator as compared with 3dB gain . Coherent demodulation requires changes of the channel estimation to track the channel response . This paper estimates and improved OFDM channel based on the Fast Fourier Transform (FFT) algorithm . FFT - based interpolation various interpolation algorithm complexity and performance tradeoff method in practical applications has been widely appreciated. This paper first analyzes OFDM systems , FFT-based time -frequency domain two-dimensional letter Road estimated algorithm matlab platform structures OFDM system , study the based on the FFT channel estimated algorithm 's performance , and compare the different conditions of the channel is estimated algorithm performance the impact . For FFT-based channel estimation algorithm in actual systems unable to obtain accurate information channel , resulting in a lack of precision of the estimated results , estimation method based on FFT-based interpolation proposed two improved algorithms , one for the pilot position at the channel estimation algorithms for specific improvements , another improved algorithm is adaptive filtering using FFT interpolation channel estimation based on the minimum mean square (LMS) algorithm adaptive channel estimation . LMS algorithm based on the minimum mean square error (MMSE) criterion is an optimization algorithm, based on changes in the statistical properties of input signals , and continuously adjust the filter weights , in order to achieve optimal output . The research results show that the adaptive channel FFT-based estimation algorithm , has a strong anti-multipath fading characteristics can fast-track the fast fading channel , low complexity and easy to implement , there is a good prospect of application .

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