Vertical handoffs in wireless overlay networks
Vertical handoffs in wireless overlay networks
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DOI：
10.1023/a:1019197320544
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发表时间：
1998-12
影响因子：
3.8
通讯作者：
M. Stemm;R. Katz
中科院分区：
文献类型：
--
作者：
M. Stemm;R. Katz
没有单一的无线网络技术同时向大量移动的用户提供低延迟、高带宽、广域数据服务。无线覆盖网络--一种由房间大小、建筑物大小和广域数据网络组成的分层结构--以高效和可扩展的方式解决了向大量移动的用户提供网络连接的问题。小区的特定拓扑和包括无线覆盖网络的各种网络技术提出了在先前的蜂窝切换系统中没有遇到的新问题。我们已经实现了一个垂直切换系统，允许用户在无线覆盖网络的小区之间漫游。我们的目标是为用户提供尽可能长时间的最佳连接，并在切换过程中将中断降至最低。我们的初步实施的结果表明，切换延迟是有界的发现时间，时间量之前的移动的主机发现，它已经进入或退出一个新的无线覆盖。这个发现时间以秒为单位：大到足以破坏可靠的传输协议，如TCP，并在连续的多媒体传输中引入重大中断。为了有效地支持应用程序，不能容忍这些中断，我们提出了增强的基本方案，显着减少发现时间，而不假设任何知识的特定信道特性。对于房间大小和建筑物大小的覆盖之间的切换，这些增强导致大约170 ms的最佳情况下的切换延迟，在网络资源方面的开销为1.5%。对于建筑物大小和广域数据网络之间的切换，最佳情况下的切换延迟约为800 ms，开销同样很低。
No single wireless network technology simultaneously provides a low latency, high bandwidth, wide area data service to a large number of mobile users. Wireless Overlay Networks - a hierarchical structure of room-size, building-size, and wide area data networks - solve the problem of providing network connectivity to a large number of mobile users in an efficient and scalable way. The specific topology of cells and the wide variety of network technologies that comprise wireless overlay networks present new problems that have not been encountered in previous cellular handoff systems. We have implemented a vertical handoff system that allows users to roam between cells in wireless overlay networks. Our goal is to provide a user with the best possible connectivity for as long as possible with a minimum of disruption during handoff. Results of our initial implementation show that the handoff latency is bounded by the discovery time, the amount of time before the mobile host discovers that it has moved into or out of a new wireless overlay. This discovery time is measured in seconds: large enough to disrupt reliable transport protocols such as TCP and introduce significant disruptions in continuous multimedia transmission. To efficiently support applications that cannot tolerate these disruptions, we present enhancements to the basic scheme that significantly reduce the discovery time without assuming any knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these enhancements lead to a best-case handoff latency of approximately 170 ms with a 1.5% overhead in terms of network resources. For handoffs between building-size and wide-area data networks, the best-case handoff latency is approximately 800 ms with a similarly low overhead.