Research Of Channel Estimation Algorithms Based On OFDM System

In the current wireless communication networks, orthogonal frequency division multiplexing (OFDM) technology has been applied to all areas of life, such as asymmetric digital subscriber loop (ADSL), Digital Video Broadcasting (DVB), digital audio broadcasting (DAB), wireless local area network (WLAN), they all have used this technique. In the fourth generation mobile communication system, OFDM technology is becoming one of its core technologies.Estimation and equilibrium technology is one of the key technologies in the OFDM system.This papper studies intensively on channel estimation algorithm in the time variant channel of the OFDM system.The may work goes as follows:(1)The paper describes the characteristics of wireless channel and the corresponding various models in detail.Then, it analyzes the affect of the Doppler frequency shift and time-varying effects in the signal transmission and time-varying channel characteristics of the OFDM system.(2)The paper analyzes the LS,MMSE,Wiener filter and SVD algorithm,and compares the performance simulation;this paper also analyzes the affect of the pilot pattern in the pilot-based channel estimation methods.(3)The paper proposes a channel estimation algorithm to adapt fast time-varying channel characteristics.The ideology of algorithm goes as followsw:firstly, we estimate the channel states at the polit by using ZF equalizer estimation and the states are recognized as the initial value;secondly,we calculate and update the weighting factor of time-varying channel status at the base of decision value of the sending signal;at last,we track the time-varying effect by combining the weighting factor and LMS channel estimation results together. And its simulation results show that the algorithm has good resistance to delay spread and Doppler shift.