歷年發生的大型天然災害中，行動通訊系統常常會因為道路、橋樑、電力的損毀而導致嚴重癱瘓，進而影響災後救援工作的進行，行動通訊系統其實是不可靠且極為脆弱的。為使災區能夠快速地恢復通訊，本研究提出一種應急通訊系統，利用無線通訊，將這些無連線能力的基地台連接起來，並利用存活可連至核心通訊網路的基地台，建構成為一個臨時性的通訊系統，稱為應急蜂巢式行動通訊網路(Contingency Cellular Network，CCN)，供使用者在災區內進行通訊。由於資料庫的可靠度在行動通訊網路中具有舉足輕重之地位，本論文旨在利用分散式架構提高CCN網路資料庫的可靠度，進而提高系統可靠度。我們先分析資料表的特性，並依據各資料表的特性以及資源之多寡，設計相應的分散式架構。
我們利用樹狀拓樸的簡單特性，提出三種分散式架構：(1)用於群組資料表的階層備援式架構、(2)用於HLR資料表的階層備援式架構，以及(3)用於HLR資料表的鄰近階層備援式架構。這三種架構都利用了樹狀拓樸的簡單特性，大幅簡化了資料庫的查詢及更新程序。我們以可用度及平均總成本，以評估各架構在不同的情形下之最合適架構，並觀察在各架構下，其系統可用度與平均總成本之間的關係，由結果可知，在群組資料表儲存架構中，若追求高系統可用度，可選擇高儲存密度之架構，反之，若追求較低的成本，可選擇低儲存密度之架構。而在HLR資料表儲存架構中，階層備援式的系統可用度與平均總成本比鄰近階層備援式來得高，表示階層備援式耗費較多成本，但可用度也較高，故在建置時可依實際情況來選擇合適的架構儲存。
最後，為驗證分散式資料庫架構之可行性，我們利用數部筆記型電腦及Android平台手機來建置階層備援式及鄰近階層備援式架構，並測量在此二種架構下於通話建立時所耗費的時間，從模擬結果可知，此二種架構皆可快速建置並可立即通訊，惟鄰近階層備援式所耗費的通話建立時間略長，但仍在可容許範圍之內。 / When stricken by a catastrophic natural disaster, the efficiency of disaster response operation is very critical to life saving. The efficiency of disaster response operation is greatly depending on communication systems. However, they were usually not dependable, including cellular networks, and often crashed due to power outage and backhaul link breakage. The failure of communication systems caused a big coordination problem to many disaster response operations. This thesis proposes a Contingency Cellular Network (CCN) by connecting isolated base stations to survival base stations using long-range wireless links to recover part of cellular network functionality. People can use their own cell phones for emergency communication in the disaster areas. CCN will be able to support a large number of disaster responders with limited resources in the early hours of disasters, thus to save many lives.
Because the reliability of database plays a very important role in the CCN, this thesis proposes a distributed database architecture to improve the reliability of database so as the reliability of CCN. We take advantage of the simplicity of CCN tree topology to design three distributed database architectures: (1) Hierarchical Redundancy Architecture for “Group_Member ” table, (2) Hierarchical Redundancy Architecture for “HLR” table, and (3) Hierarchical Neighboring Redundancy Architecture for “HLR” table. The tree topology greatly simplified the query and update procedures. We use availability and average total cost to analytically evaluate all three architectures trying to identify the most appropriate architecture under different circumstances. Based on our evaluation results, CCN operators can choose the most appropriate architecture according to their realistic circumstances.
Finally, in order to verify the feasibility of the proposed architectures, we implemented a simplified prototype using several laptops and Android mobile phones. The Hierarchical Redundancy Architecture and the Neighboring Redundancy Architecture were implemented. The results show that both architectures can be functional with reasonable performance except that Hierarchical Neighboring Redundancy Architecture may take longer time, but in a tolerable range, to setup a call.
| Identifer | oai:union.ndltd.org:CHENGCHI/G0101971014 |
| Creators | 張宜蘋, Chang, I Ping |
| Publisher | 國立政治大學 |
| Source Sets | National Chengchi University Libraries |
| Language | 中文 |
| Detected Language | English |
| Type | text |
| Rights | Copyright © nccu library on behalf of the copyright holders |
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