Research On LTE Femtocell Downlink Resource Allocation And Interference Management

Nowadays, our daily life has been changed ubiquitously with the development of wireless communication. So far, LTE networks have been deployed in the world widely. Despite its advantages of high date speed and large covering areas outdoors, LTE networks do not work well indoors for some signal fading reasons.Femtocell is a kind of small cell, which solving the disadvantages of LTE networks indoors. It connects to the core network with broad band, and can use the same frequency with macro base stations, such that femtocell users can connect to femtocell networks without mode switching technology. In the introduction of femtocell, the heterogeneous network brings new problems and challenges, the most important one of which is interference management. In the heterogeneous network, not only the cross layer interference due to using the same resource blocks between base station and femtocell, but also the same layer interference between femtocells should be managed.First, a brief introduction of the interference management background in heterogeneous networks is given in this paper; then, the interference scenarios and resource block deployment scenarios are analyzed and described. Two aspects of the interference management of femtocell in LTE networks are mainly studied.1) By adding the different resource block needs of femtocell into the model and converting the nonlinear model into linear model, an algorithm about femtocell down link interference management based on bandwidth requirements is studied. According to the SINR of macro users, the available resource blocks of femtocell is firstly determined, so as to achieve the management of cross layer interference. After that, in order to maximize the effective utilization of resource blocks, an optimization model is established. Then, convert the nonlinear model into linear model for the initial allocation, and allocate the rest resource blocks according to the result of initial allocation. Simulation results show that the algorithm can meet the requirements of femtocell with fewer resource blocks and improve the effective utilization of resource blocks.2) Through the initial centralized allocation and distributed power adjustment, an algorithm about phased down link power control of femtocell is studied. First, a distributed power control for each femtocell is executed, aiming at maximizing throughput of each femtocell with the condition of the transmit power limit, and then adjust the transmit power according to the SINR of macro users. Finally, to increase the effective access ratio to resource blocks, use an index function made by constraints to adjust the transmit power greedily. Simulation results show that the algorithm can guarantee the communication quality of macro users while increasing the whole throughput and effective access ratio to resource blocks.