Interference Management Technology Between Macrocells And Femtocells

After entering the3G period, the coverage of the indoor area becomes thesevere problem. Femtocells are the user-installed low-power, low-cost indooraccess points which can solve the coverage issue and increase the throughputat the same time. However, great challenges, especially intra-tier andcross-tier interference, prevent the femtocells to perform perfectly.This thesis studies the interference management of the femtocell cellularnetworks in both uplink and downlink. In the uplink, based on the open access,the thesis proposes a novel open access mechanism using greedy algorithm. Ittakes the limit of the backhaul into consideration, promises the profit of bothmacro users and femto users, eliminates the big interferer effectively andremoves the “dead zone”. It compares the novel mechanism with the closedaccess and the hybrid access and shows that our novel mechanism performsbest. In the downlink, based on the closed access, using the principle of theopportunistic communication, the thesis proposes four main opportunisticaccesses: SIR-based, channel-based, interference-based and rank-basedaccesses. Each access selectively sets some femtocells on and others off andthus decreases the interference and increase the throughput. All the accessescan improve the performance in varying degrees. Among all the introducedaccesses, SIR-based access performs best, increasing the throughput with30%.The theoretical threshold of the SIR-based access is also given. It is testedthat the performance of the theoretical result approximates to that of theoptimal result based on the simulation, which greatly improves therealizability.