Dynamic Power Allocation for Downlink Interference Management in a Two-Tier OFDMA Network

We study the downlink interference problem in a two-tier orthogonal frequency-division multiple-access (OFDMA) system. Assume that macro- and femtotiers share the same spectrum and that the femtotier uses a closed-access scheme. Cross-tier and intercell interference in the two tiers is investigated. Resorting to game theory and variational inequality (VI) theory, we formulate the problem mathematically and design algorithms for the solution. With the algorithms, the femto base stations (FBSs) can dynamically allocate their power according to the feedback from the macrotier to avoid cross-tier interference and to adapt to intercell interference. The overall power allocation of the femtotier reaches an equilibrium, provided that every FBS aims to maximize its own Shannon capacity. The algorithms can be distributively implemented and can mitigate the interference quickly without unnecessary performance loss. Simulation results are provided to demonstrate the performance of our algorithms and to compare with other related algorithms.