Study On Interference Management In Two-Tier Femtocell Networks Based On Power Control

Femtocell, also called “home base station”, is the low-power base station installed inbuilding or at home. Femtocell technology plays an important role in solving the problemof indoor coverage, decreasing the cost of cellular coverage and improving the quality ofwireless coverage. In two-tier femtocell networks, due to the shard spectrum, closedaccess, and unplanned deployment, the cross-tier interference aggravates. Meanwhile, thedifferent access priorities and service requirements of macrocell users and femtocell users,together with the self-configuration and self-optimization characteristics of the two-tierfemtocell networks, make the traditional interference management mechanism for cellularnetworks not applicable, and put forward new requirements for its interferencemanagement. Moreover, power control is the major method to interference management intraditional celluar networks.Firstly, the thesis studies the interference management problem with the cross-tierinterference threshold set at the macrocell base station, and proposes an interferencemanagement scheme based on maximum power adaptation. Jointly considering thecross-tier interference suppression and the femtocell users’ utility optimization, thisscheme ensures the protection of macrocell users’ uplink communication and theoptimization of femtocell users’ transmission power. Moreover, admission control isintroduced to enable the more reasonable utilization of the system resources. Simulationresults show that, compared with SINR adaptation scheme, the proposed scheme improvesthe mean satisfaction of femtocell users and their overall performance.Secondly, in view of the neglecting of macrocell base station’s utility optimization inexisting interference management algorithms based on the cross-tier interference thresholdat macrocell base station, the thesis aims at jointly optimizing the utility of macrocell basestation and the utility of individual femtocell user, and proposes a Stackelberg game basedinterference management scheme. Based on the backward induction, the macrocell basestation’s optimal interference cap is obtained and the femtocell users’ power allocation isoptimized. Simulation results show that, compared with non-cooperative method, this method not only suppresses the cross-tier interference effectively, but also improves thethe macrocell base station’s utility and the femtocell users’ average utility.Lastly, without the assumption that the macrocell base station sets its cross-tierinterference threshold, the thesis studies the interference suppression through joint powerallocation of both macrocell users and femtocell users. Considering their difference accesspriorities and service requirements, a hierarchy game based power allocation scheme isproposed. Based on the backward induction, the game equilibrium of the proposedhierarchy game is obtained. Moreover, the thesis designs the distributed power allocationalgorithms for macrocell users and femtocell users, and analyzes the running process ofthe hierarchy game. Simulation results prove that, by the proposed scheme, two types ofusers achieve their optimal power allocation and obtain their desired SINR targets,respectively.