在行動隨意網路(Mobile Ad Hoc Network，MANET)的網路環境上，資料的傳遞必需靠著多跳式(multi-hop)機制來運作，許多路由協定也因此而生，不過這些路由協定在資料傳輸路徑的選擇上面臨著兩難的處境，必需在路由路徑(routing path)的長度與可靠度(reliability)中做出抉擇。然而，現今MANET網路中，大多數的路由協定大都選擇較短的路徑進行資料傳遞，卻可能因此遭遇路由路徑容易斷裂的問題，導致行動節點必需重新找尋路由路徑，不僅浪費網路頻寬，也降低了網路產能(throughput)。本論文針對路由路徑的可靠度做考量，提出一種分環式(ring-based)路由路徑選擇機制，主要是依據相鄰兩行動節點間連線的存活時間選擇路由路徑，並且將此機制實際應用於需求式路由協定DSR(Dynamic Source Routing)上，模擬結果顯示，加上此機制的路由協定，可增加網路產能，路由可靠性亦有效的提升。尤其在行動節點移動速度較快的條件下，效能更為顯著。

In the Mobile Ad Hoc Network (MANET) data transmission usually is operated by multi-hop mechanism. Developing an efficient policy for routing path selection is an important issue in MANET, which involves several conflicting factors for which a trade-off must be found. Recently, many researchers have presented routing protocols that select the path with shortest length. Unfortunately, these protocols encounter the route fragility problem and bring the re-search process of the routing path. Thus these extra workload not only wastes bandwidth but also decreases throughput. In this paper, we introduce the ring-based selection mechanism that selects routing paths according to the link lifetime between two mobile nodes. Moreover, the proposed mechanism is implemented in an on-demand routing protocol, DSR, by the network simulator NS2. The simulation results show that routing protocol with our mechanism can increase network throughput and improve system reliability for the cases of higher mobility.

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