Complexity-reduced Single Sideband and Narrowband Doppler Spectrum Filtering Method for ATG Fading Channel Simulation

Fast Fourier Transform (FFT) based Doppler filtering is widely applied for the simulation of Doppler spectrum of fading channels. In the en-route scenario of air-to-ground (ATG) communication systems, the Doppler power spectrum is single sideband and narrow-band. Under this scenario, the complexity of existing FFT based Doppler spectrum filtering algorithm may be prohibitively high. In this paper, we propose a complex-reduced FFT based Doppler spectrum filtering method with the strategy of frequency shifting (FS) and phase compensation (PC) to solve this problem. In our proposed method, FS is first performed to make the resulted maximal absolute Doppler frequency equals to the bandwidth of Doppler power spectrum. FFT based Doppler filtering is then constructed with respect to this frequency shifted single sideband Doppler power spectrum. Finally, interpolation in time domain and PC are used to compensate the frequency offset due to the operation of FS. Analysis shows that the order of FFT filter of our proposed method is much lower than that of the existing FFT based Doppler filter. Meanwhile, simulation results show that the proposed method can obtain the same statistical characteristics as that of the existing methods.