异构网下基于速度的自适应垂直切换算法研究

在异构网络垂直切换中一直存在着乒乓效应、网络利用率低和丢包率严重等问题．以往的算法虽然提出了改进的方法，但是没有考虑移动节点速度不同对切换效率的影响，在此提出了一种自适应主动预测的垂直切换算法．采用代价函数对可接入网络进行评估和选择；根据稳定周期、移动节点运动的速度和所处位置来自动调整切换执行时间，使移动节点能自适应的进行切换抉择．仿真结果表明，该算法可以有效地减少切换延时、分组丢失以及切换次数，能够有效地提高系统的切换性能。

Research on an adaptive velocity-based vertical handoff algorithm in heterogeneous networks

The ping-pong effect, low utilization rate and the network packet loss have been serious problems in the heterogeneous networks＇vertical handoff. Although the previous algorithms have improved the methods, they did not consider the effects of different speeds of mobile nodes on the handoff. In this paper, we proposed an adaptive, initiatively predictive vertical handoff algorithm. It adopts a cost function to evaluate and select available networks, and adjusts the handoff performance time automatically in the light of its stable period, mobile node＇s velocity and location. And then the mobile nodes can make handoff adjudgement adaptively. The simulation results show that the algorithm can effectively reduce the switching delay, packet loss and switching frequency, and effectively improve the performance of the system.