Research On Downlink Resource Allocation Of Femtocell In Lte System

According to statistics, most of the voice services and data services in a cellular network occurs in the indoor environment. However, the operators have been facing the problem of poor indoor coverage, resulting in the loss of many customers. So, how to control costs under the premise of improving indoor coverage is a serious challenge for the operators. To compensate for the lack indoor coverage for traditional macro cell base stations, the concept of home base station is proposed. The home base station is also called femtocell. It is a simplified picocell and installed directly by the users in their home.Home base stations can solve the users’ demand for high-speed data services in the indoor environment. But at the same time, as the introduction of home base station in the traditional macrocell network leads to changes in the network topology, interference problems will be followed. If the interference problems (including the interference between the macrocell and the home base station, and the interference between the home base stations) can not be well solved, the overall performance of the network is still very poor. So, Research on interference management issues as well as resource allocation scheme in femtocell has great significance.In order to solve the interference problem in home base station network, The3GPP proposed a series of interference coordination technology, including schemes of the frequency domain, the power domain, and time domain. This article makes research on interference coordination based on frequency allocation scheme. There are three traditional home base station network frequency allocation scheme: co-channel allocation scheme, orthogonal channel allocation scheme and partial channel allocation scheme.The co-channel allocation scheme can make good use of the frequency resources, but interference problems are serious. Orthogonal channel allocation scheme although reduces the interference between the femtocell and macrocell, but the spectrum utilization is not high. Although partial channel allocation scheme combines the advantages of both the above, system spectrum utilization is still not high. All of the above schemes have failed to solve the following two problems:mutual interference between the home base stations; fading characteristics of PRB resources.This article summarizes some of the existing frequency allocation technology schemes and proposes an adaptive frequency allocation scheme in femtocell network. The scheme firstly determines interference relation in femtocell network measuring interference information, then uses the idea of clustering to divide lots of femtoells into sereval clusters and determines available frequency resources of each cluster, finally achieves the allocation of resources within each cluster using graph coloring algorithm. The algorithm fully considers the fading characteristics of PRB resources in OFDMA system as well as unfixed characteristic of femtocell network, solves downlink interference in femtocell network well and improves the system spectrum utilization. This article also completes the system-level simulation of LTE femtocell network and compares schenme performance. Simulation results show that the dynamic frequency allocation scheme greatly improves network performance.