在無線感測網路中，感測節點將所收集到的資料送往 sink。然而當許多鄰近的節點感測到同一事件並且傳送給 sink 時，事件影響的區域通往 sink 的路徑會需要代傳許多類似的封包，而造成不必要的能量消耗。本論文中提出了一個透過區域收集點 (Local Collection Node) 收集資料的方法。資料封包先被集中到感測區域附近的收集點，收集點再將所收集的事件起迄時間送到網路唯一的索引點。當 sink 需要資料時，再透過索引點把查詢封包轉發給擁有資料的收集點，並由收集點將資料傳回給 sink。每個節點對事件封包具有不同的吸引力，資料封包被送往吸引力較高的節點，因此吸引力較高的節點，便成為收集點。吸引力是透過建立在虛擬座標上的公式計算出。吸引力的公式因為事件而不同，如此便可以分散收集點儲存事件的負擔。模擬結果顯示，當事件影響範圍較大時， 使用本論文中提出的方法，可以節省許多額外的封包傳送和能量消耗。

In wireless sensor networks, sensor nodes send event data to sink nodes. However, when several neighboring nodes sensed the same event and send the sensed data to a sink node, the nodes on the path from the event region to the sink node have to forward many similar data packets, and unnecessary energy costs are introduced. In this thesis, data packets are collected by local collection nodes. Each local collection node sends its collected data to a globally-known index node after it received the event data. When a sink needs to obtain some event data, it sends a query packet to the index node. The query packet will be forwarded to the local collection node which has the request data. Then the local collection node transfers event data to the sink node. Data packets are forwarded to the local collection nodes based on the attraction value of nodes, which can be computed by an attraction function. When a node want to forward its sensed data packet to the local collection node, it uses the attraction function to compute the attraction value of neighboring nodes and forwards data packets to the neighboring node with the highest value. Simulation results show that our proposed scheme has a superior performance in control overhead and number of data packet forwards to previous work.

CHAPTER 1 INTRODUCTION 7
CHAPTER 2 PREVIOUS WORKS 10
CHAPTER 3 DATA DISSEMINATION WITH LOCAL DATA COLLECTION 13
3.1 LOCAL DATA COLLECTION 16
3.2 PROMINENCES IN THE ATTRACTION FUNCTION 21
3.3 THE UPDATED VIRTUAL COORDINATES 24
CHAPTER 4 SIMULATIONS 33
CHAPTER 5 CONCLUSION 40

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