A Two-Dimensional FFT Precoded Filter Bank Scheme

This work proposes a new precoded filter bank (FB) system via a two-dimensional (2D) fast Fourier transform (2D-FFT). Its structure is similar to Orthogonal Time Frequency Space (OTFS) systems, where the OFDM transmitter is changed to a filter bank multi-carrier (FBMC) one, thus obtaining a lower out-of-band emission. The complex orthogonality of the FBMC transmission is guaranteed by using pre-coding based on a discrete Fourier transform, which is also used to implement the two-dimensional fast Fourier transform. Furthermore, due to the filtering process, the proposed system obtains a good error performance using a simple equalizer in the time-frequency domain. In this sense, we also introduce a hybrid receiver in the proposed system to exploit this feature. First, the time-frequency domain equalization is performed, followed by an interference cancellation on the delay-Doppler domain. Using the delay-Doppler domain detection, the simulation results show that the proposed system obtains an error performance similar to the OTFS system. Already using the simple equalizer in the time-frequency domain, the proposed scheme presents great advantage compared to the OTFS with the same equalizer in the studied scenarios.