Efficient use of limited spectrum is emerging as a major issue in wireless systems. The proposed work focuses on technologies that provide better understanding of wireless networks and greatly enhance spectrum efficiency. with three coupled thrusts: (i) wireless network modeling; (ii) mechanisms for efficient spectrum sharing; and (iii) exploiting enhanced spectrum efficiency for wireless video communications. The project also includes an experimental research component in which the developed approaches will be implemented and tested on the cognitive radio testbed hosted at Virginia Tech and the cooperative networking testbed hosted at NYU-Poly.<br/><br/>The proposed research plans to systematically investigate several of the unique technical challenges and open problems in enhancing radio spectrum efficiency, and supporting emerging video services. This fundamental research will support the development of technologies that achieve new levels of efficiency and quality in wireless broadband services, and will help alleviate the wireless bandwidth limits now being experienced. The work is supported by the Industry Advisory Board as well as individual industry members of the center and has the potential to extend the centers portfolio. The PIs plan to disseminate the work to their industry members and the broader industry and academic community via open-source software as wel as introduce the content within their degree and outreach programs.