Research On Mobility Managements For Heterogeneous Decentralized Mobile Networks

Due to the explosive growth of mobile data traffic in recent years,the heterogeneous decentralized mobile network architecture has become a general trend which is widely accepted.The heterogeneous decentralized mobile networks could save high costs of network hardware upgrades,as well as satisfy the requirements of the tremendous increase of mobile data traffic either in the radio access network layer or in the core network layer.This architecture greatly improved the system throughput,service quality and network reliability by traffic offloading.However,the new network architecture brings great challenges to the traditional mobility management.This thesis focuses on the radio access network layer and the core network layer,proposes the corresponding enhanced mobility management strategy respectively.The main research contents of this thesis are summarized as follows:Focusing on the heterogeneous convergent networks of small cells in the radio access network layer,this dissertation presents an enhanced handover strategy for heterogeneous convergent networks of small cells based on the users' history information.In the heterogeneous convergent networks of small cells,the handover frequency of highly mobile users is extremely high,and their residence time in some cells is very short,these unnecessary handover procedures will cause a lot of signaling waste.Based on the historical information of the mobile user with redundant route,this thesis designs an effective LTE neighbor list management scheme.Firstly,a new LTE neighbor list is designed based on the existing standards,and then the maintenance scheme of the list as well as the handoff strategy based on the list are both proposed.The simulation results represent that the enhanced handover strategy reduces the probability of the short residence time tremendously,and saves the signaling cost caused by unnecessary handovers.In view of the decentralized core network architecture,this dissertation proposes a gateway selection algorithm based on user plane and control plane.The decentralized core network brings the selection problem of the optimal core gateway(P/S-GW).The traditional gateway selection strategy will not guarantee the continuity of the real-time service session,what's more,it will also lead to the signaling waste caused by the frequent unnecessary gateway selection processes.In this thesis,based on the two aspects of user plane and control plane,a cost-effective optimal gateway selection algorithm is proposed.Firstly,the decision factors of gateway selection are determined and normalized.Then the weight of each factor is calculated based on the fuzzy decision matrix,also the gray correlation coefficient and grey correlation degree are calculated.Finally,we will choose the optimal gateway based on the gray correlation degree.The simulation results show that this algorithm can reach both lower delay of data transmission and better continuity of real-time service while guaranteeing low frequency of gateway congestion as well as limited signaling cost,which means it's more cost-effective than other solutions.