Resource Allocation In Femtocell Assisted Two-Tier Network

Recent research has shown that most of voice services and data services take place in indoor environment. In order to provide high data rate and satisfied user experience, the application of so called Femtocell base station has been considered. Femtocells are usually comprised of small size, low-power, low-cost, and short-range home base stations. They work in the licensed frequency bands, are customer-owned wireless data access point deployed by terminal consumer and are connected to broadband Internet backhaul. As Femtocells can meet customer’s demand and indoor coverage requirement well, they have been widely used in many wireless communication standards, such as WiMAX, and LTE/LTE-Advanced.In practice, there are still some technical challenges to be further addressed before widespread deployment. A two-tier Femtocell network is usually implemented by sharing frequency rather than splitting frequency between tiers. Hence cross-tier interference (CTI) and inter-tier interference (ITI) are the key issues in two-tier Femtocell networks, and maximization of the total data rate of Femtocells with the consideration of cross-tier and inter-tier interference is an ongoing research area.In this paper, we address the problem of sub-channels allocation in OFDMA two-tier Femtocell networks. Our objective is to maximize the rate sum of multiple Femtocells with consideration of cross-tier interference between macrocell and multiple Femtocells. A resource optimization approach based on Ant Colony Optimization Algorithm is proposed to implement the solution process of system. Simulation results show that the proposed algorithms not only improve the capacity of the Femtocell system but also provide good proportional fairness among the Femtocell users, as compared with the traditional algorithm.On the other way, the power control problem for the co-channel deployed Femtocells is investigated. We first model the uplink power control problem as a non-cooperative game, where co-channel interference is taken into account in maximizing the energy-aware utility. By introducing a convex pricing function of the cross-tier interference, Pareto improvement can be obtained. Furthermore, based on the non-cooperative game, we devise a distributed power allocation algorithm together with an optimal price seeking algorithm. Simulation results show that the proposed algorithm can improve user utilities significantly, compared with existing power control algorithms.Finally, this paper summarizes the whole work and points out the next step research content.