Research On Resource Allocation And Access Selection Algorithm In Femtocell LTE System

With the rapid development of technology and the popularization of LTE, people desire to communicate with others with better Qo S and higher transmission rate. As the demand of indoor communication is increasing rapidly, the indoor coverage problems in mobile network is attracted more attention. To increase the transmission rate and improve the Qo S, the femtocell is introduced into LTE. At the same time, the deployment of femtocell can also offload the traffic from marcocell network. The existence of co-tier and cross-tier interference in heterogeneous network composed by macrocells and femtocells is becoming a hot issue.We firstly elaborate the key technologies of LTE and the characteristics of femtocell respectively, analyze the interference scenarios of the heterogeneous network, and then introduce several existing interference coordination technologies. In the thesis, research is focused on the downlink interference management and femtocells access selection in the heterogeneous network.To solve the spectrum resource allocation problem in the heterogeneous network with consideration of downlink interference, a hybrid algorithm consisting of Simulated Annealing(SA) Algorithm and Ant Colony Optimization(ACO) Algorithm is proposed. The algorithm which combines advantages of the SA algorithms which has an excellent ability to solve the optimization problem and the ACO algorithm which converges fast in later period improves the transmission rate of the system by allocating the spectrum reasonably. After pre-allocating the resource block which keeps users’ basic communication, we generate a pheromone matrix by using SA algorithm, by which the allocation scheme of the remaining spectrum resource is got using ACO algorithm. The simulation results show that the proposed algorithm not only improve the system capacity but also provide good fairness among the femtocell users compared to the traditional algorithms.Followed by a selection scheme for serving BS in densely femtocell system with open access mode is studied to mitigate the downlink interference among the femto BSs and the macro BS. After classifying femtocells and users according to interference information in the system, the algorithm selects appropriate femtocell for users. With frequency allocation and power control, it further reduces the co-tier interference in the system effectively. Simulation results show that the proposed algorithm can significantly reduce the interference in the system as well as improving the system capacity.