Delay and Doppler Shift Joint Tracking Method for OFDM Based Aeronautical Communication Systems

The aeronautical wireless channel can be modeled as a sparse double-selective channel, which includes a strong line-of-sight (LOS) path and a weak reflected diffuse path Compared with the LOS path´s, delay and Doppler shift of the reflected path are more difficult to be estimated, which are time-varying and non-stationary. With equalization using non-sufficient delay and Doppler shift estimation, OFDM system will be faced with serious inter-carrier interference (ICI). To obtain more accurate channel estimation values, we discussed the time-varying characteristic of delay and Doppler shift, and proposed a delay and Doppler shift joint tracking method based on extended Kalman filter. The simulation results show that the proposed method can track the channel parameters accurately, with fast convergence speed. Monte-Carlo simulations were also carried out to evaluate the BER performances of OFDM systems with our proposed tracking method in the typical two-ray aeronautical channel, and zero-force equalization was adopted to cancel ICI. The simulation results justified effectiveness of the joint tracking method.