Less Is More: Creating Spectrum Reuse Opportunities via Power Control for OFDMA Femtocell Networks

Femtocell is a promising technology which can significantly improve the spectrum efficiency and system capacity of wireless cellular networks. However, densely and randomly deployed femtocells may experience severe interfemtocell interference due to rough-and-tumble spectrum reuse with unconstrained transmit power. Different from traditional macrocell scenarios, there is no central controller available for femtocell networks. Moreover, a static planning scheme is not workable here due to random network topology. Based on game theory, we propose a sophisticated downlink power control scheme which creates more spectrum reuse opportunities among mutually interfering femtocells and enables a flexible spectrum reuse scheme. The power control problem is modeled as a generalized Nash equilibrium (NE) problem, and we employ variational inequality theory to analyze it. Existence and uniqueness properties of the NE solution are derived. Furthermore, a distributed channel-aware power control algorithm is proposed to create spectrum reuse opportunities for femtocells interfering each other. Numerical results suggest that a significant capacity improvement is acquired, and the NE point can be reached within a few iterations.