Based on the analysis of decision-directed （DD） channel estimation by using training symbols, a novel DD channel estimation method is proposed for orthogonal frequency division multiplexing （OFDM） system. The proposed algorithm takes the impact of decision error into account, and calculates the impact to next symbol duration channel state information. Analysis shows that the error propagation can be effectively restrained and the channel variation is tracked well. Simulation results demonstrate that both the signal error rate （SER） and the normalized mean square error （NMSE） performance of the proposed method are better than the traditional DD （DD＋ LS） and the maximum likelihood estimate （DD＋ MLE） method.
The aeronautical en-route communication channel is modeled as a two-ray double-selective channel. Based on the channel model, a low-eomplexity iteration self-cancellation algorithm is proposed to cancel the inter-carrier interference （ICI） of orthogonal frequency division multiplexing （OFDM） system in aeronautical communications. ICI can be completely suppressed by the proposed algorithm if channel parameters are estimated ideally. We analyzed the SNR loss with variant iteration times theoretically, and pointed out how to choose the optimum iteration times. The algorithm is especially useful to the situation with high aviation veloc- ity, as less iteration is sufficient to separate the interference with larger Doppler shift, and less noise will he introduced. We carried out Monte Carlo simulation with typical aeronautical en-route channel, and the simulation results are in agreement with the deduced theoretical performance expressions and validate the effect of our cancellation algorithm.
