Research On Algorithm Of Channel Estimation In OFDM System

Orthogonal frequency division multiplexing (OFDM) technology is a special kind of multiple carrier transmission technology. In recent years, it has been regarded as an important part of the fourth generation mobile communication technology, because it has good ability of anti-multipath interference and good utilization of broadband. However, in the actual mobile communication system, the channel characteristic is changing with the time. In order to guarantee that the original signal can be restored in the receiver, the accurate channel estimation must be carried out. This paper mainly researched the channel estimation based on training sequence and the channel estimation based on implicit training sequence.Firstly, channel estimation based on cycle mismatch sequence is proposed based on the study of channel estimation based on cycle PN sequence.The energy of cycle mismatch sequence mainly concentrates in a few pilot points, so cycle mismatch sequence is inserted into the OFDM symbol as training sequence, then in the receiver mismatch sequence in a few pilot points is picked up, and channel is estimated by related calculation beteeen mismatch sequence and cycle shift sequence of mismatch filter. Compared with the channel estimation based on cycle PN sequence, the performance of channel estimation based on cycle mismatch sequence is simulated through computer.Secondly, channel estimation method combinating cycle mismatch sequence and gaussian radial basis function is put forward. Channel impulse response in the pilot subcarrieris is calculated through the channel estimation method based on periodic mismatch sequence, then channel impulse response in all subcarriers is calculated through the gaussian radial basis function interpolation algorithm. Compared with the two kinds of algorithms, its performance is simulated through computer,.Finally, an improved channel estimation method based on the periodic implicit training sequence is proposed based on the study of traditional channel estimation based on the implicit training sequence. Training sequence is added into the sending information periodically, then the receicered signal is sampled periodically,superposited and averaged, and channel is estimated through the wiener estimation. Compared with the old algorithm, the performance of the improved algorithm is simulated through computer.