臺灣博碩士論文加值系統

在wireless ad hoc network中，Dynamic Source Routing Protocol(DSR)只在mobile hosts需要傳送資料時才開始運作。當source node需要傳送資料到destination node時，source node進行route discovery，尋找至destination node的route。當source node獲得至destination node的route後，就可以利用該route傳送資料至destination node。DSR中每一個data packet都記錄著source node至destination node的完整路徑。列於route上的nodes收到data packets，只負責轉送，不須進行路徑的選擇。DSR使用cache縮短source node獲得route的時間及減少routing時所產生的control overhead。但DSR的cache並沒有一個timer-based mechanism to expire stale routes，因此cache中可能存有out-of-date的routing information。實際上兩個已不在彼此的wireless radio range內的nodes，cache卻記錄這兩個nodes仍為連接的狀態。node從cache中找到的route就可能包含broken link。利用含有broken link的route傳送資料，packet loss ratio就會增加，反而降低performance。理想上，我們希望當link的兩個端點不再保持連接時，cache中相對應的link也剛好移除。因為每個link保持連接的時間隨著兩端的nodes任意移動而有所不同，所以cache中相對應的link的timeout值也應隨著nodes的移動而改變。在本篇論文中，我們針對DSR，提出一個設計link cache timeout的方法。假設網路中每一個節點都配備有GPS receiver。當node需要傳送packet時，會將自己的GPS information加入packet中。收到packets的nodes利用packets內與自己相鄰的node的GPS information 及自己的GPS information，估計兩個nodes之間維持連接的時間。DSR使用cache mechanism可以減少control overhead，但cache中的stale route information提高了data packet loss ratio。在control overhead與data packet loss ratio為trade-off的狀況下，考慮較少的control overhead，又能維持較低的data packet loss ratio，本篇論文提出的方法正可以符合這樣的要求。

目錄
圖表目錄iii
表格目錄iv
一、IntroductionP. 1
1、簡介ad hoc networksP. 1
2、ad hoc networks上的routing protocolsP. 1
(1)Table-driven routing protocols in ad hoc networksP. 1
(2)on-demand routing protocols in ad hoc networksP. 1
(3)兩者差異P. 1
3、Cache mechanism的使用for on-demand routing protocolsP. 1
4、選擇DSR討論的理由P. 2
5、DSR基本運作及其optimizationsp. 2
(1)DSR的基本運作 -- Route Discoveryp. 2
(2)DSR的基本運作 -- Route Maintenancep. 3
(3)DSR的optimizationsP. 3
6、caching strategies -- path cache與link cacheP. 4
(1)static link timeoutP. 5
(2)adaptive link timeoutP. 5
7、簡述論文結論P. 5
8、論文架說明P. 6
二、MethodologyP. 7
1、DSR基本運作P. 7
2、Mobility Prediction using GPS informationP. 7
3、Additional information in the packetsP. 7
(1)GPS information of transmitting nodeP. 7
(2)the timeout between two nodesP. 8
4、node actionsP. 8
三、Simulation EnvironmentP.12
1、network circumstances and node mobility modelP.12
2、traffic load modelP.12
3、simulated methodsP.12
4、performance metricsP.13
四、Simulation resultsP.14
1、varying number of nodes in the networkP.14
2、vary traffic loadP.17
3、vary node mobilityP.21
4、observationsP.23
五、ConclusionsP.26
六、ReferencesP.27
圖 表 目 錄
圖表一Route Discovery的過程P. 8
圖表二control overhead varying with number of nodesP.14
圖表三data packet loss ratio varying with number of nodesP.15
圖表四route acquire time varying with number of nodesP.16
圖表五control overhead varying with the idle period of each nodeP.17
(busy period固定為10秒)
圖表六 data packet loss ratio varying with the idle period of each nodeP.18
(busy period固定為10秒)
圖表七route acquire time varying with the idle period of each nodeP.18
(busy period固定為10秒)
圖表八control overhead varying with the idle period of each nodeP.19
(busy period與idle period比例為1：1)
圖表九data packet loss ratio varying with the idle period of each nodeP.19
(busy period與idle period比例為1：1)
圖表十route acquire time varying with the idle period of each nodeP.20
(busy period與idle period比例為1：1)
圖表十一control overhead varying with node mobilityP.21
圖表十二data packet loss ratio varying with node mobilityP.21
圖表十三route acquire time varying with node mobilityP.22
表 格 目 錄
表格一performance metrics varying with number of nodesP.23
表格二performance metrics varying with the idle period of each nodeP.23
(busy period固定為10秒)
表格三performance metrics varying with the idle period of each nodeP.24
(busy period與idle period比例為1：1)
表格四performance metrics varying with node mobilityP.24

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