Theoretical Analysis of the Power Spectral Density for FFT-FBMC Signals

Filter-bank multicarrier (FBMC) modulation is appreciated for its spectrum well-localization. However, the drawback of FBMC is the presence of the intrinsic interference that prevents the application of some multiple input multiple output techniques. Recently, fast Fourier transfrom (FFT)-FBMC was proposed to get rid of the intrinsic interference by performing FFT/IFFT (i.e., inverse fast Fourier transform) precoding and postcoding on each subcarrier. Consequently, FFT-FBMC affects and modifies the spectrum of the transmitted signal. In this letter, we address the power spectral density (PSD) of the FFT-FBMC transmitted signal. We theoretically derive the expression of the PSD of FFT-FBMC signal. We also show that the FFT precoding of the signals on each subcarrier has the advantage to reduce the frequency band occupied by each subcarrier. Consequently, we will show that FFT-FBMC spectrum is more frequency-localized than that of the conventional FBMC.