無線網狀網路中路由協定的效能量測

Abstract

無線網狀網路(Wireless Mesh Network) 結合了ad hoc網路和 infrastructure網路的兩者優勢，它是由多個網狀存取點(Mesh Access Point)和網狀客戶端(Mesh Client)組成。 在無線網狀網路裡Mesh Access Point可以使用ad hoc的介面來與其他Mesh Access Point溝通，而Mesh Client會透過infrastructure模式來與Access Point做連結。為了幫助轉送從Mesh Client來的封包，Mesh Access Point使用ad hoc路由協定來建立路由路徑。在Access Point中，主要是由“Wireless Mesh Routing”(WMR)來決定路由，如果在網狀網路裡的WMR 採用一個沒有效率的路由協定，那無線網狀網路的可能將會獲得很差的效能且失去了擴充性，由此可見WMR 對無線網狀網路而言是非常重要的。 在這篇論文裡， 我們使用NCTUns 網路模擬器來模擬這些經常使用在無線網狀網路裡的路由協定，例如OSPF，AODV和STP。 在比較這些路由協定的模擬結果之後，我們發現OSPF最適合用在無線網狀網路的路由協定，但是它仍然有一些問題存在，因此我們提出一個架構叫做Multi-Gateway且引入RoofNet的ETX來幫助OSPF的路由協定，進而改進無線網狀網路的效能。

The wireless mesh network combines both the advantages of ad hoc networks and infrastructure networks. It is composed of multiple mesh access points and mesh clients. A mesh access point in the wireless mesh network uses an ad hoc mode wireless interface to communicate with other mesh access points, and mesh clients connect to its neighboring mesh access points by using the infrastructure mode wireless interface. In order to forward data packets from mesh clients, mesh access points use the wireless mesh routing protocol to construct the routing path. “Wireless Mesh Routing” (WMR) is the main component in an access point that decides how to route packets. The performance and the scalability of a wireless mesh network may be poor if WMR in the mesh network adopts an inefficient ad hoc routing protocol. Therefore, WMR is very important to wireless mesh networks. In this paper, we used the NCTUns network simulator to evaluate several commonly used routing protocols in wireless mesh networks, such as OSPF, AODV and STP. After comparing the simulation results of these routing protocols, we find OSPF is the most suitable protocol for wireless mesh networks. However, it still has some problems. Therefore, we propose a multi-gateway architecture and apply the ETX metric to the OSPF routing protocol to improve the performance of the wireless mesh network.