Research On The Key Technologies Of Mobility Management In Heterogeneous Networks

The convergence and interworking of heterogeneous network is one of the most important trends of future networks. The convergence and interworking of networks is the foundation of the network evolvement, the mobility management technology is the most critical technology to support terminals, services and users'mobility. The challenge faced by the study on the network convergence and interworking, mobility management technology including the heterogeneous characteristic of networks, multiple rapid emerged radio access technologies. This is reflected on the following aspects, not only network architectures, protocol of network interfaces, security mechanism, QoS control, but also the improvement of the coverage, data rate, and mobility support of those new radio access technologies. Regarding the current research works of the network convergence and interworking, some aspects still need more investigation. Firstly, the advantages and disadvantages of current proposed interworking architectures are obvious and none of those architectures has made good trade off between security, mobility support capability and the cost of implementation. Secondly, there is no secure, easy to use mechanism can be used for user access control and authentication. Current methods also can not satisfy the requirement that subscribe only once while roaming to any network worldwide. Third, the vertical handover mechanism needs more optimization. Fourth, the newly designed the access node, such as home base station, also needs mobility management to ensure the commercial operation. Based on above consideration, the selected study areas of this dissertation are the most important areas and the study on those areas is necessary from the theory and practical point of view. Based on the systematical summarise and analysis of the latest researches on the architecture for interworking of heterogeneous network and critical mobility management technologies, this dissertation focuses on the issues of the interworking architecture of mobile communication network and WLAN, user access control and authentication, the vertical handover optimizations and the mobility management of home base stations and so on.The major contributions of this dissertation are as following:1) Interworking architectures of mobile network and WLAN and its critical technology. Based on analyze of four interworking architectures, e.g. tight coupling, loose coupling, hybrid coupling and peer integration, the comparisons of the global roaming support, security, handover, location management, QoS and implementation cost of above architectures were made. Semi-tight coupling architecture was proposed in this paper. Related critical technologies such as global roaming, access control and authentication, mobility management were proposed. Analyses result shows that new architecture is feasible.2) Access control and authentication. According the study of the security of the GSM, GPRS, UMTS and IEEE 802.11, advantages and disadvantages of the security aspects of mobile communication network and WLAN are compared. Based on the semi-tight architecture, a new access control and authentication method was proposed. After introduced the global roaming support for users of mobile network and WLAN, the usage of mobile network to convey the signaling of access control and authentication, the seamless global roaming and increased security level of the interworking are achieved at same time. The related tests in the test bed has validated the new method.3) Cross-layer handover optimization. A cross-layer address configuration method to improve network layer handover performance was proposed. Currently, the movement detection and address configuration's delay almost equals to the handover delay. By binding layer two information with preserved network layer care of address, the terminal can select the preserved network address according current access network's layer two information, so the access router discovery, address configuration and duplicate address detection can be skipped during the network layer handover procedure. Theoretic and numerical analyses results show that the delay of network handover was decreased dramatically almost to the same magnitude of the delay of layer two handover by the new method.4) Mobility management of home base station. One location locking mechanism was proposed based on the semi-tight coupling architecture. User terminal module was equipped to home base station, during the access procedure of the module, the current location was decided by the network and the network authorize that home base station can working at that location or not via the terminal module. In order to mitigate the mobile attack during the normal operation of the home base station, the characteristic of the mobile attack was analyzed and related mathematical model was proposed. Based on the model, the period of periodical location reporting is decided, and the terminal module is required to perform periodical location reporting to trigger the network to validate home base station's current location. Analyze result shows this method can prevent mobile attack in time with limited signaling costs.This work is supported by:National High-technology (863) Program of China (No.2005AA121510,No.2006 AA01Z229,No.2006AA01Z209, No.2007AA01Z222).