Distributed Power Control in Femtocell-Underlay Cellular Networks

In a two tier cellular network comprised of a central macrocell underlaid with shorter range femtocell hotspots cross-tier interference limits overall capacity with universal frequency reuse. To quantify near-far effects, this paper derives a fundamental relation providing the largest feasible cellular signal-to-interference plus noise ratio (SINR), given any set of feasible femtocell SINRs. A distributed utility-based SINR adaptation at femtocells is proposed in order to alleviate cross-tier interference at the macrocell. The Foschini-Miljanic (FM) algorithm is a special case of the adaptation. Each femtocell maximizes their individual utility consisting of a SINR based reward less an incurred cost (cross-tier interference). Results show greater than 30% improvement in mean femtocell SINRs relative to FM. An algorithm is proposed that adaptively curtails transmission powers of the strongest femtocell interferers. Simulations show that a cell-edge user can achieve its SINR target even with 100 femtocells/cell-site (with typical cellular parameters).