Dynamic Spectrum Access (DSA) plays a key role in the coexistence of heterogeneous networks at a maximum level of mutual interference and with a guaranteed Quality of Service. This project sets out to devise and evaluate theoretical tools and algorithms with potential impact on DSA and the resulting performance metrics. A number of research lines are identified, mainly related to the physical and medium access layers, but also targeting network-level issues, addressed from a combined application of Signal Processing and Information Theory tools.