Nowadays, several global navigation satellite system (GNSS) services coexist at L-band and some more will be available in the near future. These new signals were originally conceived to enhance the location accuracy, but they also offer a promising opportunity for improved GNSS-reflectometry (GNSS-R) retrievals. This work gives closed form expressions for GNSS-R waveform simulation using the composite GPS L1 and L5 and Galileo E1, E5, and E6 signals as function of the receiver bandwidth. The impact of the observation geometry and sea state on the waveform shape is studied in airborne and spaceborne conditions. Finally, the altimetric height bias using the derivative method is analyzed as function of the receiver bandwidth.