There is no doubt that wireless communication technologies have been one of the most interesting innovation fields in the telecommunications industry in recent years. The spectacular rate of innovation in this field has enforced the vision of ubiquitous connectivity: the vision of a world where every human being and every electronic device, from high-end supercomputers to tiny sensors of temperature in your car, can talk to each other through a dense web of communication links. A vision of this kind, although more “human-centric,” is proposed, for example, in the “Book of Visions” (2001) published by the Wireless World Research Forum. Of course, wireless communication technologies are instrumental in accomplishing this vision, as we cannot possibly imagine to connect everything by means of cables. Moreover, wireless communications offer the advantage of supporting mobility even at high speed.