Dynamic Spectrum Sharing among Femtocells: Coping with Spectrum Scarcity in 4G and Beyond

The ever-growing demand for mobile broadband is leading to an imminent spectrum scarcity. In order to cope with such situation dynamic spectrum sharing and the widespread deployment of small cells (femtocells) are promising solutions. Delivering such a view is not short of challenges. Massive deployment of femtocells in an uncoordinated way will create difficult interference scenarios.

For these reasons, this PhD thesis investigates how each femtocell can autonomously select portions of the spectrum in order to achieve more spectral efficiency and fairness. The solutions also strive for scalability to a large number of cells, stability and limited complexity. The work represents an evolution towards future cognitive femtocells.

The issue of inter-cell interference among femtocells is thoroughly analyzed with game theory, graph theory and system-level simulations. These analyses show that the interference should be managed, and the frequency reuse should be dynamically adapted locally. Three different methods are proposed. Two of them completely avoid the need for signaling among different cells, and the third method involves the setting of mutual agreements among neighbor cells. These methods allow attaining both high average throughput and high outage performance. Overall, they can be seen as future enablers of truly ubiquitous mobile broadband.