Research On The Handoff Technology In Heterogeneous Wireless Internetworked Networks

With the rapid development of wireless communication technology, network accessing typesdiverse increasingly, different kinds of networks emerge, which has prompted a long-termcoexistence and collaboration among a variety of network. Complementary function multi-networkintegration will be the development trends in the future. Vertical handoff is the key technology ofnetwork convergence. The pros and cons of vertical handoff performance directly determinewhether the user can enjoy the quality of service. Therefore, the ability to ensure that the end-userscan access in the most appropriate time with the optimal network so as to enjoy the best QoSbecomes a standard for measuring switching performance. However, the complexity of thenetwork, the dynamic nature of the terminal state, and the diversity of applications has broughtmultiple challenges for the switching technology.This thesis study technologies of vertical handover in-depth and propose appropriate solutionsfor some existing problems. Main contents are as follows:1. The shortcomings and technical bottlenecks of switching technology are discussed. Basedon the understanding of switching impact on the end-user quality of service, from the user point ofview, considering battery level, network cost and other factors, we proposed an adaptive handoverdecision algorithm, which can reduce the number of unnecessary switching, effectively extend theworking time of mobile terminal. The new algorithm solves the problem that, due to the lack ofelectricity, users can not enjoy high-quality services.2. In the integration of heterogeneous wireless network, there is a problem of low resourceutilization. To solve it, we developed a vertical handoff algorithm to dynamically allocate thebandwidth resources. According to the traffic types, by the help of access control technology andhandover management technology, the new algorithm allocates bandwidth resources dynamicallyso as to maximize resource utilization under the premise of ensuring terminal QoS.3. Combining signal prediction and fuzzy control theory, we proposed a vertical handoveralgorithm to improve the handover trigger timeliness in a fast fading heterogeneous interworkednetwork. It predictes signal with gray prediction theory to improve the accuracy of the handovertrigger timeliness issue. Using fuzzy logic, it dynamically quantizes and weights the handoverdecision parameters, considering the network and terminal parameters, it select the optimal target network so as to implement a high-performance handover. It especially fits for a fast fadingheterogeneous wireless interworked network environment.