Research And Optimization On Spectrum Allocation In Two-tier Femtocell Networks

Femtocell is a kind of micro base station which is widely studied according to the trend of broadband mobile development, to provide better service quality for the users of the indoor scenes such as family and business office. In two-tier macrocell and femtocell networks, spectrum allocation is critical to the practical application of the femtocell system. How to allocate spectrum to reduce the cross-layer interference between macrocell and femtocell and the mutual interference among femtocells, raise the spectrum efficiency and increase the capacity of the system is the point of this paper.In this paper, the author analyzes the configuration scenarios and interference model in two-tier macrocell and femtocell networks, proposes two methods of spectrum allocation, one method is the spectrum allocation in two-tier femtocell networks based on soft frequency reuse(SFR). This method can be divided into two steps, first of all, the macrocell apply SFR, the center area of the macrocell and the border area of the macrocell assigned with different power to improve the performance of the macro users. Then, an improved femtocell spectrum allocation method is proposed in femtocell to reduce interference between the macrocell and femtocell. Another method is mix with spectrum allocation and power allocation in femtocell system. First of all, the algorithm uses the adaptive fractional frequency reuse method to allocate spectrum, and then introduces the principle of water injection, under the premise of the total power is limited in accordance with the existing sub-channel allocation, allocate the power of sub-channel to achieve a better system capacity. Simulation results and analysis of the proposed spectrum allocation algorithms show that the algorithms can reduce the cross-layer interference between macrocell and femtocell and the mutual interference among femtocells and improve system performance.