無線隨意網路 - Mobile Ad-Hoc Networks(MANETs)是由一群無固定基礎建設的行動通訊裝置集合而成，由於沒有固定的無線網路基礎建設，在傳遞資料上便顯得比較困難。而隨選路由通訊協定(On-Demand Routing Protocol）與表格驅動路由通訊協定(Table-Driven Routing Protocol)是二種有效的尋找路徑方法，Ad-hoc On-Demand Distance Vector Routing（AODV）、Dynamic Source Routing（DSR）、DSDV(Destination-Sequenced Distance-Vector Routing)與ZRP(Zone Routing Protocol)都是其中最具代表性的方法。然而，不論是隨選路由通訊協定或是表格驅動路由通訊協定都是專注在如何獲得有效的路由路徑，卻忽略了當路由失效時，重建路徑所浪費的時間與資源。
    因為在無線隨意網路下裝置會隨意的移動，所以網路的拓樸會時常變化、一直的變化，也因此路由失效的機率將增加，使得路徑重建的次數也隨之升高，因此所浪費的路由重建時間與封包的傳遞是相當可觀的。而且當傳遞的資料是即時性的資料(Real time data)型態時，也會因為延遲時間的長短而出現問題，所以當傳遞資料時，中斷再傳遞的情形在無線隨意網路下常常發生，卻不是每種資料型態都可以接受的。
    本文提出一種以預防性的備用路由(Backup Routing)方式，推測傳輸路由可能將要中斷或是Delay，而在中斷或Delay之前預先找好另一條路由路徑，並在發生中斷之前，改變原先的傳遞路徑到已經找到的備用路徑以達到資料的持續傳輸。經研究發現，同樣在五十個裝置而且通訊範圍是五十公尺的情況下，傳遞不斷訊的時間增加了47%，在通訊範圍增加至一百公尺時，傳遞不間斷的通訊時間增加53%，在通訊範圍增加至一百五十公尺時，傳遞不間斷的通訊時間增加63%。

In Mobile Ad Hoc Networks, On-Demand Routing Protocols are effective routing protocols. Ad-hoc On-Demand Distance Vector Routing (AODV) [1], Dynamic Source Routing (DSR)[2] , DSDV(Destination-Sequenced Distance-Vector Routing) and ZRP(Zone Routing Protocol)are the most typical methods. 
    These methods are focus on how the routing path to find but ignore that when the routing path is invalid, the resource wasted in rerouting is very much, and may cause a delay. When we transmit important data packets, high transmission performance is necessary. So if we know the tolerance of the important data packets, we have to prevent the broken occur as best as we can.
We provide a scheme, back routing on-demand, to prevent and delay or broken and search a new routing path On-Demand in advance. Before delay or broken, we can change the routing path in advance and expect to continue transmitting. And the scheme can extend the transmission time to not to break and improve the total transmission time. When the communication distance is 50 meters and total nodes are 50, the transmission time improves 47%. Extend to 100 meters, it improves 53% and it improves 63% when the one-hop distance extends to 150 meters. When the nodes increase, the transmission time improves better.

目 錄
一、緒論	1
1.1. 研究背景與動機	1
1.2. 研究目的	10
1.3. 研究架構	10
二、文獻探討	11
2.1. AD-HOC ON-DEMAND DISTANCE VECTOR ROUTING（AODV）	14
2.2.	DYNAMIC SOURCE ROUTING（DSR）	18
2.3.	AODV與DSR之比較	22
三、實驗方法	25
3.1. 路由探索階段	25
3.2 資料傳遞階段	26
四、模擬與分析	30
五、結論	38
REFERENCE	40

圖 目 錄
圖 1. 主從式無線區域網路	2
圖 2. 無線隨意網路架構	3
圖 3. PROGAGATION OF RREQ IN AODV	16
圖 4. REVERSE PATH FORMATION.	17
圖 5. PATH OF THE RREP TO THE SOURCE IN AODV	17
圖6. BUILDING OF THE ROUTE RECORD DURING ROUTE DISCOVERY.	21
圖 7. PROGAGATION OF THE ROUTE REPLY WITH THE ROUTE RECORD.	21
圖 8. ROUTING DISCOVERY IN OTR.	26
圖 9. REROUTING.	28
圖 10. 較短的REROUTING PATH.	30
圖 11.  50 NODES IN 1000*1000 METERS	32
圖 12. 80 NODES IN 1000*1000 METERS.	33
圖 13. 100 NODES IN 10000*1000 METERS.	34
圖 14. COMMUNICATION DISTANCE IS 50 METERS.	35
圖 15. COMMUNICATION DISTANCE IS 100 METERS.	36
圖 16. COMMUNICATION DISTANCE IS 150 METERS.	36
 
表 目 錄
表 1. DSR與AODV的比較	23
表 2. THE TOLERANCE OF THE VOICE COMMUNICATION USERS	27
表 3. THE ACTION AFTER NODES SENDING OR RECEIVING	29
表 4. 模擬參考一覽表	31

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