Abstract:

Under air-to-air high-speed mobile communications,the Doppler frequency shift of the Aerial platform has characteristics of a large range and rapid change.It is difficult for existing frequency estimation algorithms to tackle both high estimation accuracy and engineering realization feasibility.In this paper,the time-varying Doppler frequency shift model is first constructed according to the traditional frequency offset model and the spatiotemporal correlation of Doppler frequency shift versus time.Based on this model,the coarse frequency offset estimation values of adjacent short preambles are associated.The optimization problem of frequency offset estimation is transformed into a classic optimization problem of overdetermined linear equations,which reduces the estimation variance to the maximum extent and improves the estimation accuracy.Simulation results show that the residual frequency offset of the proposed algorithm is reduced significantly compared with the traditional algorithm.Simulation results show that the root mean square error(RMSE) of the proposed algorithm is less than 100 Hz when the SNR is greater than 5 dB.Aiming at the numerical stability problem existing in the proposed algorithm,the corresponding engineering realizable method is given in the paper.Unlike the traditional phase-locked loop feedback tracking scheme,the proposed algorithm adopts a feedforward compensation scheme,thereby improving the system stability and timeliness.

Key words: high speed mobile communication, frequency offset model, frequency offset estimation, frequency offset tracking