The paper considers the comparison of orthogonal frequency division multiplexing (OFDM) and high speed downlink packet access (HSDPA) techniques in the physical layer of a satellite system devoted to the provision of digital multimedia broadcasting (DMB) services. In particular, the paper demonstrates that the inherently high spectrum efficiency of OFDM can be retained even in unfavorable propagation channels affected by heavy non-linear and linear distortion, respectively introduced by the on-board high power amplifier and by frequency selective propagation. This encouraging performance, achieved through the proper design and application of coding and pre-distortion techniques, is compared with the standardized HSDPA radio interface for 3G terrestrial mobile networks, and is shown to be in line on non-selective channels. Advantages for OFDM are demonstrated in frequency selective channels, using low complexity equalization in the frequency domain