Research On Non-blind Channel Estimation Algorithm For WiMAX

With the emergence of multimedia services like data, images, video, etc, the bandwidth and performance requirements continue to increase; A series of technical standards for the appropriate introduction, WiMAX comes. WiMAX using OFDM, adaptive modulation and coding, QoS mechanisms and other advanced technologies. If want to display their advantages, there must be other technologies such as channel estimation technology. Channel estimation based on whether the use of training sequences or pilot is divided into non-blind, blind and semi-blind channel estimation. This paper studies the non-blind channel estimation algorithm using OFDM physical layer.Channel estimates are based on the characteristics of the wireless time-varying channel and it impacts on system performance, so this paper introduces wireless channel characteristics first.Then, estimate the channel information using the preamble and pilot of data symbols. In the course of calculating the frequency domain response of pilot sub-carrier, it discussed the LS algorithm, MMSE algorithm. Based on the above results the papers discussed different algorithm like linear interpolation, sinc interpolation and DFT interpolation algorithm. Then, analyze the performance of their algorithms through the Matlab software.Finally, in order to suppress noise on the impact of channel estimation, using low-dimensional Kalman filter in time domain for each sub-carrier to estimate, using the minimum mean square error criterion in the frequency domain complete of all the pilot channel estimates. Get the whole channel frequency response through the second-order linear interpolation algorithm. Then reduce the computing complexity of the estimating results using the channel characteristics of sub-carrier frequency domain. Based on the above algorithm, use preamble-Pilot joint channel estimation algorithm, the estimation result is the optimal one, because the pilot estimation result corrects the preamble's one.