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Author: 曾維祥
Wei-shyang Tseng
Thesis Title: 無線應用網路中路由機制之研究
On-Demand Routing in Wireless Access Networks
Advisor: 邱舉明
Ge-ming Chiu
Committee: 陳秋華
none
李良德
none
Degree: 碩士
Master
Department: 電資學院 - 資訊工程系
Department of Computer Science and Information Engineering
Thesis Publication Year: 2005
Graduation Academic Year: 93
Language: 中文
Pages: 50
Keywords (in Chinese): 無線隨意網路無線接取網路需求繞線協定
Keywords (in other languages): on-demand routing protocol, wireless ad hoc network, wireless access network
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  • 由於MANET是一種具有彈性、自我組織且多步傳輸特性的網路架構,以MANET來延伸具基礎建置的無線網路是很適合的。因此,結合上述兩類網路變成一項熱門的研究領域,這種網路我們又常稱之為無線應用網路(wireless access network)或是混合隨意網路(hybrid ad hoc network)。在這種網路中,不在閘道器傳輸範圍內的行動節點,可以藉由多步傳輸的特性與閘道器通訊。而行動節點至閘道器的傳輸採用AODV這種需求(on demand)方式的繞線協定,可以減少過於頻繁的路徑維護所造成的繞線負擔。但是AODV的運作機制在無線應用網路中會造成“繞路”的問題,另外,經由氾濫請求訊息的路徑搜尋程序亦造成另一種的繞線負擔。
    本論文乃針對AODV在無線應用網路上發展一套有效的繞線機制。為了防止因為繞線維護時所產生的“繞路”問題,我們修改AODV中繞線更新的原則,我們的想法是採用目的端序號與到目的節點的步數並重的方式,來避免一個有效的路徑被更新為一個較長的路徑,而產生的“繞路”現象,此外,我們以到閘道器的步數為判斷請求訊息的傳送方向,而避免浪費過多的訊息往不必要的區域傳送,以完成有效率的路徑搜尋程序。最後,我們以模擬的方式驗證機制的效能並與其他方法比較之。


    The flexibility, self-organization and multihop transmissions of MANET are well suited to extending service area of gateway (or access point) in infrastructure-based networks. The research area about integration of MANET and infrastructure-based networks becomes popular. In such environment, commonly known as wireless access networks or hybrid ad hoc networks, mobile hosts outside the transmission range of the gateway can communicate with the gateway via multihop transmission. On-demanding routing protocol like AODV has been used for routing between gateway and mobile hosts because of their low routing overhead. However, routing path between them tends to detour. It means that packet transmits along longer path instead of shortest one. In addition, mobile hosts discover routes about gateway via a flooding technique inducing another kind routing overhead.
    In this thesis, we present a novel extension of the AODV routing protocol. To avoid phenomena of detour resulted from route maintenance, we modify the rule of route update in AODV. The basic idea of our mechanism is to consider both destination sequence number and hop count to prevent a valid path from being updated to a longer path. Besides, to limit route request scope, we uses hop count which represents number of hops to reach destination to guide our route request message toward gateway. It can help for eliminating route message dissemination toward unnecessary areas. In the end, several simulations are made to validate the performance of our mechanism and compare with previous methods.

    第一章 緒論 1 1-1. 背景 1 1-2. 論文目標 7 1-3. 論文架構 10 第二章 相關研究 11 2-1. Proactive方式 11 2-2. Reactive方式 13 2-3. Hybrid方式 14 2-4. 總結 16 第三章 AODV繞線機制與繞路現象 18 3-1. AODV繞線機制 18 3-2. 繞線更新 22 3-3. 繞路的現象 23 第四章 繞線機制 26 4-1. 繞路現象與目的端序號 26 4-2. 解決繞路問題的機制 31 4-3. RREQ轉傳局部化機制 33 4-4. 整體系統之演算法 37 第五章 效能評估與模擬結果 39 5-1. 模擬參數及環境設定 41 5-2. 固定位元率流量形式之模擬結果 42 5-2-1. 「資料流量的來源端數目」對應「正規化繞線負擔」 42 5-2-2. 「資料流量的來源端數目」對應「封包送達率」 43 5-2-3. 「資料流量的來源端數目」對應「端對端傳送的時間延遲」 44 5-3. 開-關流量形式之模擬結果 45 第六章 結論 48 重要參考文獻 49

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