Research On The Interference Coordination For Femtocells

With the development of mobile communication technology,more and more voice services and data traffic take palce in indoor environment.The indoors coverage weakness is getting worse. There are some solutions for the indoor coverage weakness in recent years, including the relay station, a distributed antenna system and radiation cable, etc.But all of them has disadvantages. After the deployment of femtocells, the original single macro network becomes Two-tier Femtocell Networks composed of macro-femto network which makes interference among cells more diverse and complex,especially the subscribers who are locating at the edge of the cell because of they will get the interference signals from the adjacent femtocells. Using fractional frequency reuse algorithm can reduce the interference between edge subscribers. But the traditional FFR algorithm has low efficiency spectrum, which resulting that the system throughput is not very well.So it is necessary to do some research for improving the efficient of FFR algorithm.The primary contributions are as follows:(1)This thesis mainly focuses on the interference scenarios and interference management scheme in two-tier femtocell networks. Firstly, do some reseach on the basic technical principles of femtocell and the challenges after the femtocell was introduced,analyzing the classic interference scenarios of two-tier femtocell networks are and then getting the solutions for the interference scenarios. In order to reduce the interference between femtocells, having some analysising and comparison of the common interference suppression techniques, which focus on the study of fractional frequency reuse algorithm in interference coordination technology.(2)Based on the classic FFR algorithm, proposing an improved Fractional Frequency Reuse algorithm for interference coordination. According to the dense deployment of femtocells, the algorithm can adaptively adjust the center area proportion and frequency reuse factor of the edge area. The algorithm has two core parts:One of them is to adjust the center area proportion according to the dense deployment of femtocells. The FFR scheme divides the cell into cell center region(CCR) and cell edge region(CER). The Frequency Reuse Factor(FRF) of CCR is 1 and the Frequency Reuse Factor of CER is more than 1 and generally is 3 so as to mitigate the cell edge interference. At present the center area proportion of most of the FFR algorithm is fixed;Another one is to adjust the Frequency Reuse Factor of CER according to the dense deployment of femtocells. So that it can not only reduce interference but also improve the spectrum efficiency.(3) In addition, researched and determined the models and parameters required in building two-tier femtocell network simulation platform, including antenna model, path loss model, deployment model, transmitting power and so on. Simulating the algorithm which is proposed in this thesis and analysis its performance.Simulation results show that the proposed scheme can solve the interference between femtocells and significantly improve the average throughput and the average spectral efficiency of subscribers. Allocating resource block for each cluster using simulated annealing coloring algorithm.