Research On Handover Algorithms For Heterogeneous And Small Cell Networks

With the rapid development of mobile communication technologies,mobile users and business needs are increasing rapidly.In order to solve these problems,heterogeneous and Small Cell networks(HetSNets)as the current development trend of the mobile communication.In order to make user equipments(UEs)in HetSNets can roam the whole network seamlessly,it is urgent to study the integration and communication technology of wireless communication system which is suitable for HetSNets.Among them,the handover which can realize the heterogeneous network coordination and various access modes seamless connection is its important foundation and core technology,has caught the industry's much attention and become the academic research hotspot.HetSNets are multi-network systems with a three-dimensional and hierarchical structure.The self organizing feature is more obvious and the network structure is more complex.Meanwhile,some factors such as network types,technical standards and wireless environments in intra-layer and inter-laye may be variable,which lead to various types of handover.Therefore,designing a network structure with higher flexibility and lower complexity and a handover scheme which considering various characteristics and types of HetSNets have become the focus of current research.Accordingly,the research work in this paper is mainly carried out from the following two aspects:The first is the outbound handover.We used the circle of Apollonius to construct the outbound handover system model and proposed a dynamic configuration algorithm of the hysteresis margin.This algorithm can configurate the hysteresis margin dynamically based on the UE speed and avoid the early and late handover to meet different outbound handover requirements for UEs at various speeds.Experimental results show the proposed algorithm can effectively improve the performance of outbound handover in HetSNets.The second is the inter-Small Cell handover.In hyper-Dense HetSNets which have a large number of Small Cells,in order to improve the connectivity between the UE and the Small Cell and configure the hysteresis margin dynamically,we put forward a decision algorithm for the inter-Small Cell handover.The algorithm is divided into two parts,a Small Cell screening mechanism based on the channel gain and a dynamic configuration mechanism of the hysteresis margin based on the UE speed.The former can screen the Small Cell with better channel condition to maintain the connectivity between the UE and the Small Cell.The latter may configurate the hysteresis margin dynamically based on the UE speed to meet different inter-Small Cell handover requirements for UEs at various speeds.Experiments results show that the proposed algorithm can effectively improve the performance of inter-Small Cell handover.