適用於IEEE 802.11及IAPP無線網路的快速換手機制

Abstract

在以IEEE 802.11為基礎建設的網路中，換手一直是一個嚴重的問題。在這篇文中，我們將針對以IEEE 802.11結合IAPP的網路，提出一個快速且無縫的換手機制。我們所提出的方法，是結合基於neighbor graph的概念、加上一個在睡眠模式中執行選擇性掃描的方法、在換手之前預先執行認證的機制和經由加強IAPP而延伸出來的forwarding-and-buffering機制。選擇性掃描可以讓mobile host (MH)縮短掃描鄰近access points (APs)的時間；在換手之前預先執行認證的機制也可以有效縮短換手的時間；而在利用forwarding-and-buffering機制，可以避免在換手過程中，資料的遺失。經由我們的效能分析，我們所提出的方法，可以有效的減少90%的換手時間，且在換手的過程中，不會有資料的遺失。

Handoff is a critical issue in IEEE 802.11-based wireless networks. In this paper we propose a fast and seamless handoff solution for IEEE 802.11 wireless LAN with IAPP. It is based on a concept of neighbor graph, which describes the nearby access points (APs) that a mobile host (MH) may find. Then we further derive selective scanning with unicast in power-save mode, pre-registration of IAPP, and frame forwarding-and-buffering mechanisms. Selective scanning allows a MH to only try potential handoff targets. Pre-registration allows early transfer of a MH’s security context from its old AP to new AP. The forwarding-and-buffering mechanism is to solve the packet loss problem during handoff. Our performance evaluation shows that the proposed solution can result in 90% reduction in the handoff latency from standard handoff procedure.