Research On Channel Estimation Algorithms Based On Priori Information In Aeronautical Communication System

With the development of civil aviation,users' requirements for aeronautical communication services are also increasing.However,in the aeronautical communication,the high Doppler frequency offset causes time-varying fading of the channel,and subcarriers interfere with each other.The delay causes the channel to exhibit frequency selective fading,and the signal has intersymbol interference.The above two problems seriously degrade the system performance.Therefore,obtaining accurate channel state information and eliminating Doppler frequency shift interference become two key technologies for improving communication quality.At present,the common channel estimation algorithm and Doppler frequency shift estimation algorithm are accompanied by an increase in computational complexity while increasing the estimation accuracy,and lack of attention to the characteristics of the aeronautical channel.The aeronautical communication has pre-planned aircraft routes and airports.The layout can provide some parameter information for the research of communication technology.Therefore,this paper will focus on how to fully exploit and utilize the characteristics of the aviation system and the priori information provided without improving the complexity of the algorithm.The main work contents are as follows:1.In order to solve the time-varying of aeronautical communication channels,this paper proposes a scheme combining the iterative feedback algorithm with the aviation system.The method reduces the estimation error rate by continuously updating and iterating the channel and utilizing the error correction capability of the system's channel coding.The simulation results show that the proposed scheme uses a small number of original pilots to significantly improve the channel estimation performance while maintaining the low complexity of the LS algorithm.2.In order to make full use of the advantages of pre-planned aircraft trajectories and scenes,this paper proposes a scheme for channel estimation using the priori information in take-off and landing scenarios.Based on the construction of the parameter channel model,the scheme uses the channel delay in the fixed airportenvironment as the priori information to reduce the estimation parameters and computational complexity.The simulation results show that the proposed scheme can effectively utilize the parameter information provided by the system and improve the channel estimation performance,which is more suitable for aeronautical communication systems.3.For the Doppler frequency shift estimation problem,this paper proposes a scheme based on the Radio Environment Management(REM)for the frequency offset estimation using the posterior estimation algorithm,which uses the estimate from REM as the prior knowledge,and the cyclic prefix structure of OFDM is utilized to provide a maximum a posteriori estimate.The cyclic prefix takes the data portion of the delay interference removal.By simulating and analyzing the performance of the maximum a posteriori estimation algorithm,it is compared with the REME,the classical CP-based estimation algorithm and its improved methods.The results show that the proposed method can not only overcome the delay interference,but also significantly outperform the existing method in estimating the mean square error.