Resource Management In Two-Tier Macrocell And Femtocell Networs

With the rapid development of wireless communication technology, traditional cellular communication networks can hardly satisfy users’ huge demand on much higher system throughtput. Heterogeneous netwoks, which consists of several kinds of low power nodes including picocell, femtocell and relay node, are promising solutions to solve this problem. Moreover, femtocells are expected to be widely developed and to be one of the most popular deployment scenario of heterogeneous networks as researches have shown that more than70%of the voice and data traffic is generated in indoor environments. However, the deployment of low power nodes will bring severe interference to the netwoks. What make things worse are the randomly deployed femtocells working in close subscriber mode. The severe interference will cause dramatic degradation of the macrocell and local cells’performance. Therefore, effective interference management is of vital importance for the success deployment of heterogeneous networks.The main work of this work including the following aspects:Firstly, investigations about heterogeneous networks are given, including common deployment scenario, interference problems and state of the art about interference management in industrial standardization process.Covarage of two-tier Macro-Femto networks is investigated and approximate expression of outage probability of Macro tier and femto tier is derived. First system model of co-channel deployed Macro-Femto networks is established using the spatial poission point process and stochastic process modeling. Then closed form lower bound per tier downlink outage probability is derived accounting for propagation loss, lognormal shadowing and Rayleigh fading. System level simulation is performed and the simulation result verified the accuracy of the derived per-tier outage probability.Thorough insight into cross-tier interference in co-channel deployed two-tier macro and femto networks is provided. By detaching distance dependent decay from the attenuation experienced by signal and interference, cross-tier interference to signal ratio, which is determined by deterministic system parametes, is defined to characterize cross-tier interference in the two-tier networks; cross-tier interference to signal constraint, which is determined by channel stochastic characteristics including shadowing and fading, is derived to characterize the tolerance of cross-tier interference for given per-tier signal to interference targets and outage probability constraints. The definition of cross-tier interference to signal ratios and relationship between cross-tier interference to signal ratios and cross-tier interference to signal constraints give clear and useful elucidation of cross-tier interference in the two-tier networks.For guaranteeing reliable macro and femto coverage, constraints on femtocell resource management are analyzed, including maximum density of simultaneously transmitting femtocells, maximum and minimum transmission power of femtocells as well as femtocell resource block usage constraints when femtocells are deployed too dense. A decentralized femtocell regulation strategy which is able to maximize the area spectral efficiency while guaranteeing reliable macro and femto covarege is proposed and simulation results verified the rationality of our theoretical claims and the proposed decentralized femtocell regulation strategy is able to achieve the maximum spatial reuse while providing reliable macro coverage to the whole cellular.