Mobility Management Algorithms In Cellular Heterogeneous Networks

With the rapid development of wireless communication technology, a variety of multimedia services have emerged, and the traditional cellular network cannot satisfy the traffic requirements of high date rate and low time delay. Therefore, the cellular heterogeneous network which is composed of macro cells and small cells is proposed to improve the system throughput as well as user experience, and it has attracted lots of attention due to the advantages of flexible networking and high spectrum efficiency. However, as the small cells in cellular heterogeneous network have the characteristics, such as the irregular deployment and small covering range, which lead to complex network topology structure. Consequently, frequent cell selection and handover are required, which bring serious challenges to mobility management technology. In this thesis, mobility management algorithms in cellular heterogeneous networks are studied, and the main contents are as follows:After introducing the background and related review of the cellular heterogeneous network, the mobility management technology is discussed. The difficulties and challenges on mobility management technology are analyzed, and then cell reselection and handover schemes are discussed. Furthermore, the importance and necessity of studying mobility management algorithm are stressed.Handover performance analysis based on stochastic model is conducted for the cellular heterogeneous network which consists of one macro and small base station. The proposed method analyzes the handover performance under two scenes, e.g., the random movement of user and the random change of channel. Furthermore, the relations between handover failing probability and handover parameters and user's movement speed are derived. Finally, the effects of handover parameters and user movement on handover are evaluated by the simulation analysis.Focusing on multi-user handover decisions and resource allocation of target cell, a joint cell handover and resource allocation algorithm based on the electromagnetic radiation optimization is proposed. The proposed algorithm formulates the joint electromagnetic radiation function of handover users by considering the mobility states of handover users and traffic characteristics. Moreover, the minimum electromagnetic radiation of user is utilized as the optimization objective to achieve the joint optimal target cell selection and power allocation strategy under the case of the quality of service requirements of users.