A single-carrier modulation system based on the fractional Fourier domain equalization in aeronautical channels

The channel is time-frequency-selective due to considerable relative movement between airborne communication transceivers in aeronautical communications systems. The performances based on traditional orthogonal frequency division multiplexing (OFDM) and single carrier frequency domain equalization (SC-FDE) systems are degraded because of the timing variant characteristic under time-frequency-selective channels. To get better performance, researches have been done for the OFDM system based on the fractional Fourier transform through selecting the optimal fractional order. However, the application of the method is limited because of the request of feedback link. This paper proposes a signal carrier modulation systems with equalization based on the fractional Fourier transform (SC-FRFDE), in which the feed-back link is not necessary. After description of the channel characteristic, the channel estimator and equalizer are designed according to the least squares (LS) algorithm and zero forcing criterion. Moreover, the algorithm for selecting the optimal order of fractional Fourier transform is derived. Theoretical analysis and numerical simulation results show that the system can significantly improve the performance of SC-FDE system.