無線隨意行動網路(MANET，Mobile Ad Hoc Networks) 是一種沒有事
先建置基礎架構（infrastructure），而是由無線主機所臨時組成的網路，
具有與傳統網路截然不同的特性，包括隨時可能改變的網路型態、沒有方向
或範圍限制的移動和無法預測的流量負載等。由於無線隨意行動網路架設快
速且機動性高的特點，可以運用在一些需要立即通訊的環境，像是災難現
場、戰場、或是當基地台因某此因素(停電、地震等) 而無法使用時。
由於沒有基地台(Base Station) 的架設，當兩主機之間想要互相通訊
時，必須先建立好一條路徑，這條路徑是由一連串的節點所組成，負責轉送
資料，此建立路徑的方法稱為繞徑協定(Routing Protocol)。目前已經有
許多關於繞徑協定的研究被提出來。這些協定在選擇路徑時會根據一些準
則，像是路徑的長度、品質、訊號強度、網路頻寬或是生命週期等等。本篇
論文著重在生命週期這部份。因為節點可以自由移動，所以當路徑中某一個
鍊結(Link) 因為兩端節點的移動而斷線時，這條路徑就無法使用而必須重
新建立另一條路徑。生命週期代表了一條路徑保持連線，可以使用的時間。
生命週期愈長，代表路徑的可靠性愈高。
本篇論文提出了一種預估路徑生命週期的機制，給定一條路徑，根據路
徑上每一個節點的位置，藉由隨機移動的模式(Random walk model)，推導
出移動的機率分佈，進而再評估出路徑生命週期的期望值。要注意的是，本
篇並非提出一個新的繞徑協定，我們的目標是提出一個比較可信、較符合實
際狀況且誤差較小的模型來預估路徑的生命週期。

One wireless network architecture that has received a lot of attention recently is the mobile ad
hoc network (MANET). It is attractive because the network can be quickly deployed without the
infrastructure of base stations. One main feature of MANET is that mobile hosts may communicate
with each other through a sequence of wireless links (i.e., in a multi-hop manner). While many
routing protocols have been proposed for MANET by considering criteria such as length, quality,
bandwidth, and signal strength, the issue of route lifetime has not been addressed
formally. This thesis presents a formal model to predict the lifetime of a routing path based on
the random walk model. Through such investigation, we hope to provide further insight into issues
such as route selection, route maintenance, and network scalability related to MANETs.

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