Simple mathscripts for basic fast-convolution (FC) processing and generalized FC (GFC) processing are available through the below links. The GFC processing principles are explained in J. Yli-Kaakinen et al., “Generalized Fast-Convolution-based Filtered-OFDM: Techniques and Application to 5G New Radio,” to appear in IEEE Transactions on Signal Processing 2020, 10.1109/TSP.2020.2971949 generFC.m basicFC.m