本論文提出一個稱為DECT(distributed event contour tracking)的無線感測網路分散式事件輪廓追蹤演算法。當事件發生於密度較高的感測網路中，或是事件所涵蓋的範圍較大時，會同時讓多個感測器偵測到事件並回傳資料，故此時事件會以一個範圍的形式出現在感測網路中，並且隨著時間事件可能會有移動或分佈改變等的行為，例如一群野生動物的遷徙、軍隊的行進、毒氣、化學污染的擴散等。DECT採用了有省電能力的近似最佳六角形架構(nearly optimal hexagonal grid topology)做為網路架構，並且利用這個架構的優點來偵測分布於感測區域(sensing area)內的事件輪廓，接著DECT將會收集所有分佈於事件輪廓線上的節點之資料，以追蹤事件的移動或變化。此外DECT也發揮了多匯點(Multi-sink)網路的優點來進行資料的傳送，藉由將輪廓線分段，位於輪廓線上的節點將會被分成數個段落，且每個段落的節點都會找到一個特定的匯點傳送資料。如此一來交通流量將會被疏散到所有的匯點，因此降低了資料因擁塞(congestion)而遺失的機會。而我們也對DECT做了一系列效能的模擬，並和相關的演算法做比較，來顯現出DECT的優點。 In this thesis, we propose a distributed event contour tracking algorithm, DECT (distributed event contour tracking), for multi-sink wireless sensor networks. We focus on the convex-shaped area event, which has a large effect region and may trigger many sensors at the same time. An area event may change its shape or move with time. Wild animal migration, army march, gas diffusion and chemical pollution are typical examples of area events. DECT utilizes nearly optimal hexagonal grid topology to achieve energy efficiency and to track area event contour. It finds out all sensor nodes on the event contour and collects their sensing data for tracking the event. DECT takes advantage of multiple sinks to forward data; it divides the event contour into several segments in a distributed way, and nodes in every segment will select a specific sink for transmitting reporting data. So, data traffic is dispersed and the chance of congestion and the packet dropping rate are thus reduced. We also perform simulation experiments for DECT and compare the simulated results with related ones to show the advantages of DECT.
