Downlink Power Control in Co-Channel Macrocell Femtocell Overlay

In this paper, interference mitigation through downlink power control is considered for Macrocell Femtocell overlay. Specifically, the strong interference in the downlink from the home base station to a nearby macrocell user should be properly controlled such that the quality-of-service of both the macrocell user and the Femtocell users can be guaranteed. In this work, the fundamental capacity limitation of spatial spectrum sharing among a macrocell user and a Femtocell user is identified. A downlink power control problem is formulated to address the co-channel interference, as well as provide quality-of-service to both the macrocell! user and the Femtocell users. The feasibility condition of the problem is derived and both centralized and distributed solutions are provided. Because the co-channel interference are from heterogeneous cells, a joint power control, channel management and admission control procedure is suggested such that the priority of the macrocell users is always ensured. Simulation results demonstrate the effectiveness of the proposed schemes.