This lecture is of a tutorial nature, aiming at clarifying the motivations and the benefits of introducing the array of antennas and the paradigm of software radio in the next generation of mobile communications. In addition to the conventional time, frequency and code diversity, the use of array of antennas adds the new dimension of space diversity that in perspective allows an increase of the performance of a mobile network, in terms of quality of services and subscribers capacity. Next generation universal mobile communications are likely to employ different techniques and standards. The implementation of as many as possible receiver functionalities in software appears to be the most effective solution to cope with the multiplicity of communications alternatives. The concept of Software-Defined Radio (SDR) refers to a programmable hardware to implement the receiver functionalities by different resident software or software downloaded from the network. Both approaches require advanced digital signal processing techniques and technologies, that are at the forefront of the state-of-art and in some cases are not yet available. The lecture provides the basic knowledge to understand the introduction of these two approaches in the next generation of mobile communications and the challenges posed on the digital signal processing techniques and technologies.