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Channel estimation for OFDM system with fast fading channels

An adaptive pilot insertion based frequency-domain channel estimation and equalization technique is proposed for OFDM systems with fast fading channels. The proposed method, in addition to the conventional method which averages and updates the estimated propagation characteristics on each channel, detects subchannels that are momentarily distorted by noise and intercarrier interference (ICI) over fast fading frequency-selective channels, or by the sudden intercept owing to shadowing effects. The information of the detected subchannels is used to decide whether or not to insert new pilots in the corresponding subchannels. Then we obtain the LS equalizer, and get the MMSE solution. Through simulation, we optimize the coefficients λ, α and β. The simulation results demonstrate that the method is effective for OFDM systems with fast fading channels.