Research On LTE Femtocell Interference Management Based On Resource Allocation

In recent years, with the explosive development of mobile communication network and the increasing quantity of smart terminal, the requirements of mobile users for data transmission rate of network are increasing. Femtocells deployed indoor are able to shorten the distance between base stations and indoor users, which significantly makes up the inadequacy of traditional macrocell for indoor area coverage, enhances the system throughput and provides high quality voice and data service for indoor users. As a result, femtocells have a good development prospect.The introduction of femtocell would change the topology of original macrocell network and form a double layers heterogeneous network (HetNet), which brings not only cross-tier interference between macrocell and femtocell networks, but also co-tier interference between femtocell networks. In this dissertation, research is focused on the interference management in the HetNet in the context of Long Time Evolution (LTE). In this dissertation, we first elaborate the key technologies of LTE and femtocells, analyze interference scenarios of HetNet with the deployment of femtocells, and introduce several existing femtocells interference management techniques. After that, two different resource allocation schemes are studied according to different interference scenario.For downlink cross-tier interference scenario with femtocell and macrocell sharing the spectrum, a distributed joint subchannel and power allocation scheme is studied. Through allocating radio resources to femtocell users, interference from femtocell base station to macrocell users should be kept below a tolerable threshold. The scheme using Nondominated Sorting Genetic Algorithm-2 (NSGA-2) is able to maximize not only the throughput of all femtocell users, but also the power efficiency of the femtocell base station. The simulation result suggests that the scheme has better performance in femtocell network throughput with good protection for macrocell users comparing to existing schemes.For co-tier interference management in femtocell densely deployment scenario, a cluster-based subchannel allocation scheme is studied. A weighted undirected interference graph is constructed based on the interferences between femtocells. Then the femtocells that have strong potential interference with each other are assigned to a cluster. In a cluster, a cluster head is elected to allocate the subchannels to the cluster members. Power control based on reference users is applied to keep the interference between clusters below a certain threshold. The simulation result suggests that in femtocell densely deployment scenario, clustering method is able to acquire better system throughput and satisfaction.