Research On Interference Management Technology In 5G Ultra Dense Networks

The rapid development of the Mobile Internet and Internet of Things has raised the demand of users for higher data traffic,larger coverage capacity,and higher requirements on the quality of service experience.The emerging business challenges have promoted the research and development of the fifth generation(5G)mobile communication system.As one of the key technologies in the 5G system,the Ultra Dense Network(UDN)has been designed to increase the spectral efficiency of the network through space-intensive networking of small cells,which is an effective way to increase the network capacity of future 5G system.In ultra-dense networks,the further reduction of cell coverage range,the irregular deployment of base stations and the shortened distance between network nodes make the interference more sever and diversified,posing new challenges to interference management.Based on the analysis of the characteristics of ultra-dense network,this paper analysis the major kinds of scenario requirements as well as the technical challenges in UDN in detail.In order to conduct novel studies on interference management technology,combining UDN deployment trend and characteristic,the main work of this paper includes the following three aspects.First,in this thesis,the existing interference coordination schemes are analyzed from the perspective of resource allocation including frequency domain,time domain and space domain,based on the standardized interference coordination regulations in 3GPP documents.Meanwhile,we also sum up the relevant research methods,which is related to the existing mainstream technologies.Some of the methods have laid the theoretical foundation for the subsequent studies on the resource allocation schemes that use spatial interference coordination as the primary means.Second,in order to deal with inter cell interference in ultra-dense homogeneous network,this thesis proposes a clustering-based interference coordination scheme with lower complexity.The scheme transforms interference management among network nodes into inter-cluster interference coordinate problem,and the process of cell clustering takes the change of base station density into account.In the stage of resource allocation,a sub-optimal compensation algorithm is adopted to deal with sub-channel selection problem of BSs,whose allocation standard is maximizing the SINR value.Simulation shows that the performance of resource compensation algorithm is obviously better than the initial allocation algorithm in the first phase.Thirdly,consider the imbalance of transmitting power among cells in different overlays,a mathematical model that solve average region interference is used to characterize the mutual interference among network nodes,so as to handle the downlink cross-tier and co-tier interference in ultra-dense heterogeneous networks.After that,an interference weight matrix reflecting the interference between nodes is established,based on which a new heuristic clustering scheme is proposed.The new clustering scheme is in the light of the principle of the classical MAX-K-CUT problem in graph theory.It combines network uses' resource scheduling with intra-cluster interference coordination,aiming at coordinating the base stations or user nodes in the same cluster so that their mutual interference can be mitigated.It is indicated in simulation results that the proposed resource allocation algorithm shows better system performance comparing to the traditional full or partial frequency reuse algorithm.