802.11網狀網路之實作研究

Abstract

IEEE 802.11標準規範定義了利用DSS (Distribution System Service)將許多BSS (Basic Service Set)連結後形成ESS (Extended Service Set)以提供更大範圍的連線服務。市面販賣的802.11 Access Point產品大多以Ethernet作為DSS來連結所有的 BSS。但是許多場所並沒有預留Ethernet管線給Access Point連結，例如機場大廳、古老建築及運動場等…所以，以無線方式提供DSS的需求正不斷的提升。雖然在IEEE 802.11標準規範中有定義Wireless Distribution System (WDS)所使用的封包格式，但並沒有詳細定義封包的使用方式及網路拓普結構的形成方式。 為了要活用WDS封包以達成無線的DSS，802.11 Task Group S正在定義一個基於802.11 WDS基礎上的無線網狀網路，稱為ESS Mesh。目前802.11s的規範正在以SEE-Mesh / Wi-Mesh聯合計畫書為基礎來定義標準規範。這個計畫書中設計了一系列必備的基礎功能及協定，也設計了一個可擴充的架構，為未來升級及使用者自行加強功能預留空間。 在這篇論文中，完成了一個可以形成802.11網狀網路的平台，並且提出了數個可以提升效率的改進。利用本平台，可以發現在現實環境中才能發現的問題，亦可以更實際地體驗新的技術是否有良好的效果。

IEEE standard 802.11 defined that Basic Service Set (BSS) can be connected by Distribution System Service (DSS) to form an Extended Service Set (ESS) in infrastructure mode in order to extend service area. Most of the products in the market implement DSS by connecting to Ethernet. However, requirement for deploying access point to a place without Ethernet plug is still growing. On the other hand, original 802.11 defined frames for Wireless Distribution System (WDS) but did not define how to form the topology and how to use the WDS frames. For the growing requirement of Wireless Distribution System (WDS), 802.11 TGs is now working on developing the specification of 802.11 mesh network, which is called ESS Mesh. Now, SEE-Mesh / Wi-Mesh joint proposal is a basis for 802.11s specification. In this proposal, mandatory protocol is defined under a flexible framework, which provides extensibility for future specification upgrades or user define applications. In this thesis, a platform for 802.11 mesh network is implemented, and several enhancements proposed to provide better performance. By using this platform, issues that only occurs in reality is easier to be figured out and evaluating the effect of new enhancements is more practical.