MANET中利用節點移動方向降低廣播風暴發生之路由策略

Abstract

藉由許多配備無線通訊能力的嵌入式系統裝置，如筆記型電腦、行動電話、PDA、車用導航系統及車用電腦等，不同的裝置透過無線通訊的能力，將彼此連接，構成行動隨意網路 (Mobile Ad Hoc Network) 的環境。這些網路上的節點可能任意且快速移動，隨時改變既有網路拓樸，造成原先已經建立好的路由中斷。採用被動式路由協定 (Reactive Routing Protocol) 的路由重建，往往增加了資料傳送的延遲及重建路由時所需要大量路由發現 (Route Discovery) 的封包，造成廣播風暴 (Broadcast Storm)，嚴重影響整個網路的效能。\r\n\r\n在論文中，我們提出一個利用節點的移動方向做為選擇適當中繼節點 (Relay Node) 的策略，稱之為Directive Location-Aided Routing，簡稱DLAR。DLAR將節點的移動方向因素加入於既有的LAR中做為選擇中繼節點的考量。中繼節點的決定，需要符合與來源節點相同的移動方向，目的是維持較長的連線時間，且讓路由中斷的位置靠近目的節點，並使用AODV的Local Repair的機制做為路由搜尋的協定，加速路由的恢復。\r\n\r\n實驗模擬結果顯示，DLAR與AODV、DSR及LAR比較，在減少找尋路由路徑時所需的路由請求封包、降低點對點 (End -To-End) 的延遲及資料成功送達率，都有較佳的表現。在網路中節點數較多時，DLAR在封包送達率能有6%– 55%的改善，降低搜尋及維持路由時需要的控制封包量達40%以上，降低廣播風暴發生的機率， DLAR也同時在End-to-End Delay的表現較之於其他路由機制，有20%以上的改善。

In MANET the nodes may move fast and unpredictable, this may cause the original set up route well broken. Adopt those Reactive Routing Protocols may not only cause seriously data delivery delay but also produce a large number of control packages (RREQ) thus reducing network capacity. This is known as Broadcast Storm Problem. In this thesis, we proposed a routing protocol, Directive Location-Aided Routing (DLAR), that helps to choose appropriate relay nodes (intermediate nodes) in MANET. DLAR considers the node movement direction factor in deciding a stable route. Relay node is considered to be the same movement direction as source node. The goal is to maintain longer path lifetime, and make the broken very close to the destination node. DLAR adopts AODV to discovery route and accelerate the route recovery using Local Repair mechanism. \r\nSimulations show that as the network loading is high, DLAR can increase the packet delivery ratio by 6% ~ 55 % and increase the bandwidth utility by 40%, reduce the largely broadcast storm probability, and reduce end-to-end delay by 20%.