Unlicensed Spectrum Sharing: From Coexistence to Convergence

The incorporation of unlicensed bands with licensed spectrum for mobile traffic offloading provides an effective solution to meet the ever growing data rate demands. The successful realization of harmonious multi-RATs operation in unlicensed bands requires more than mere consideration of coexistence. This has motivated us to develop Convergence of Multiple Radio Access Technologies (CONTACT), a framework for multiple RATs to explore the integration of several emerging technologies in both wireless communication and computer networking. In this article, we provide a comprehensive review of the state-of-the-art contributions from the perspective of coexistence and identify limitations. Then we present the overall design of the proposed CONTACT architecture, with an emphasis on the technical contributions. A duty-cycled convergence strategy is presented and implemented on a general- purpose-processor-based software defined radio hardware testbed. We conduct a real-world indoor experiment to demonstrate the feasibility of CONTACT. The experimental results show that the proposed strategy can achieve better performance than the existing coexistence mechanism. Finally, several open issues are identified.