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This letter proposes a neural network based channel identification and compensation methods for an OFDM system. Under the fast fading environment, pilot-aided channel estimation suffers from channel state fluctuation particularly in the last part of the packet. The proposed approach can estimate the whole transition of channel states and efficiently compensate the channel variation using the generalization capability of a neural network. The computer simulation results clarify its effectiveness via improved BER performance even under the stringent Doppler shift.

In the high mobility environment, the channel state information (CSI) in the last part of the packet is different from the beginning part's actual channel. This phenomenon degrades channel estimation accuracy, and hence it is necessary to be compensated to realize reliable communications. Decision feedback channel estimation (DFCE) has been widely considered as the channel tracking approach. It still causes estimation errors due to the decision-making process in the presence of time and frequency selective fading environments. To address these issues, this paper newly proposes a generalized regression neural network (GRNN) based channel tracking scheme incorporated with frequency-domain CSI smoothing. The latter part is the key to improve the dependability of the training data sets. Computer simulation results confirm that the proposed scheme can achieve superior BER performance and the lower root mean square error (RMSE) value of estimated CSI better than the conventional ones.

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