垂直切换的策略研究

下一代无线网络中，异构切换技术是融合多个异构接入网络的关键技术之一。近年来，随着无线通信技术的蓬勃发展，如何使用多个异构网络接口达到无缝的异构切换成为研究热点。多个接口可以采用不同的触发机制和使用规则，这将需要不同的协议实现支持并带来不同的实际切换性能。文章对异构切换中的多接口使用机制以及触发规则进行详细研究，并对不同的多接口使用机制和异构切换触发机制的4种不同组合进行仿真比较。从仿真结果可以看到，切换过程中采用链路层的信息能够及时触发即将发生的切换，另外，如果采用多个接口预先建立连接的机制，能够最大限度的减少切换延时。因此，这两种机制的组合能够带来最佳的切换效果。

Study of the Vertical Handover Policies

In Next Generation wireless networks, vertical handover techniques are expected to enable the integration of heterogeneous networks. How to make use of multiple heterogeneous interfaces to facilitate the seamless vertical handover is a hot topic in recent yeas with the development of wireless communication. Multiple interfaces can come in a variety of ways to use in accordance with different triggering scheme in the vertical handover, and may result in different requirements on protocols and performance. In this paper, the authors study multi interface schemes and triggering schemes for handover in heterogeneous wireless networks. And we simulate these schemes in NS2 to compare the handover performance. From the simulation results, wecan see the link layer information can be well used to trigger the oncoming handover in time, on the other hand, pre established multiple paths can be used to decrease the handover latency. So these two schemes combined using can produce the best performance of vertical handover.