Research On Graph-based Spectrum Allocation Method In The Heterogeneous Networks

Nowadays,we are stepping into the mobile network stage,and the mobile data requirement grows rapidly.To meet the rapid and stable communication data requirement,some low power,small coverage,low cost and flexible for multiple scenarios small base stations have been deployed in the traditional cellular network.Further the high level life quality demand expanding leads to a multi requirement to the communication service,to meet these requirements,more and more different kind of mobile device joins the communications networks,leading to a more complex network.So the heterogeneous network(HetNet),consisting of conventional macro base station(MBS)and self-organizing femto base stations(FBS),will be the dominant network style in a long period of future time.Spectrum resource,as a precious and scarcity natural resource,will be the most important constraint on the development of future communication technology.So allocating the spectrum resource suitable and efficiently will be one of the most important research fields in the future communication technology research.In the HetNet spectrum resource allocation research,the spectrum efficiency and users communication quality guarantee is a pair of trade off problems.So how to make the full use of spectrum resource while guaranteeing all the users' communication service quality is a big challenge.Further,in the future HetNets,the amount of uses will reach a huge quantity.So how to fast and efficient allocate the resource to every user is another big challenge in the future communication technology research.Graph theory,as a promising theory in transferring complex problem into simple graph max-k cut problem,has been regarded as an effective way to solve the resource allocation problem in HetNets.In the dissertation,we will discuss the resource allocation problems in two level three scenarios in the HetNets based on graph theory.The detailed works are described as follows:Firstly,for the inter-cell resource allocation problem in the HetNets,the spectrum efficiency and co-channel interference mitigation is a co-existing and mutual constraints problem.So how to maximize the spectrum efficiency while mitigating the co-channel interference is the main problem we concentrate in this part.We propose a universal frequency reuse(UFR)scheme in a two-layer HetNet to ensure good throughput for all user equipment,especially UEs at cell edge.The proposed scheme allows each cell to use all the spectrum resources,limited by an orderly regulation of all sub-bands.This scheme minimizes the potential occurrence probability of inter-cell co-sub-band interference through an intra-cell sub-band resource management.Furthermore,a graph-theoretic based sub-band allocation algorithm is developed to optimize UE throughput performance,especially for the cell-edge low signal to interference noise ratio(SINR)UEs.Simulation result shows that the UFR scheme outperforms other two schemes significantly.Secondly,the intra-cell spectrum resource allocation in tradition HetNet,spectrum efficiency and user's minimize SINR guarantee is co-existing and mutual constraints problem.How to maximize the spectrum while guarantee the user's minimize SINR is a challenge in the intra-cell resource allocation.In this part,a new downlink interference evaluation scheme is proposed,based on which a multi-target resource allocation algorithm is developed to maximize user equipment(UE)throughput in a dense femtocell deployment scenario meanwhile providing every UE a minimum SINR guarantee.The optimal resource allocation problem is formulated as a MAX-K cut problem based on the graph theory approach.System level simulations reveal that intra-cell interference is greatly reduced and the spectral efficiency is significantly improved by using the proposed resource allocation scheme.Finally,for intra-cell spectrum allocation in Ultra-dense HetNets(UDHN),how to make the resource allocation decision fast and stable is the main problem we concern.In an UDHN network,dynamic traffic patterns can lead to a high computational complexity and an excessive communications overhead with traditional universal reuse schemes.In this part,a new resource allocation scheme presenting a low computational overhead and a low sub-channel handoff rate in a dynamic UDHN is presented.The scheme first defines a new interference estimation method that constructs network interference state map,based on which a radio resource allocation scheme is proposed.The resource allocation problem is a MAX-K cut problem and can be solved via a graph-theoretical approach.System level simulations reveal that the proposed scheme decreases the sub-channel handoff rate greatly with a little network throughput degradation.