臺灣博碩士論文加值系統

能源有效率及保證覆蓋率在無線感測網路中，是兩大重要研究議題。在感測網路裡，能源是一項很重要的資源。任何能源浪費都會影響到網路的使用期長短。在一個有密集節點的網路中，一個任意的事件產生，可能使得很多偵測到它的鄰近感測器，同時傳送報告該事件的封包至資料收集處。這個動作，使得資料收集處收到許多多餘的封包（指向同一個事件）。而感測器也因為傳送這些多餘封包，而花費不必要的能源損耗。在本文中，我們提出一個新的概念，稱做責任覆蓋：每個感測器只需回報在其責任覆蓋裡發生的事件。當感測器偵測到一個事件時，根據收到的訊號強度，可決定該事件的距離，此距離即可用來判斷該事件是否落在其責任覆蓋裡。我們提出三個分散式協定讓感測器能自我決定其責任覆蓋區域大小。我們提供廣泛的模擬結果來評估我們所提協定之效能。

Energy efficiency and coverage guarantee are two important issues in sensor networks. In wireless sensor networks, energy is a scarce resource. Any energy waste will directly affect the network lifetime. In a densely deployed sensor network, an event may trigger many nearby sensors that detect this event to transmit reports, thus causing a lot of redundant reports of the same event and wasting a lot of energy resource. In this paper, we propose a concept, called duty coverage (DC), such that a sensor only needs to report an event within its DC range. Whether an event is inside a DC range is done by determining the signal strength of the event. The coverage of the sensing field will not be reduced by doing so. We propose three distributed protocols for sensors to self-organize their duty coverage. We provide extensive simulation results to evaluate the performance of our protocols.

Contents

List of Figures 1

1. Introduction 2

2. Preliminaries and Problem Definition 6
2.1 Motivation and example 6
2.2 Event distance estimation 8
2.3 Problem definition 9

3. Proposed Protocols
3.1 Overview
3.2 Coverage preservation
3.3 Solution 1 : Shrink-and-Check Protocol (SAC) 12
3.4 Solution 2 : Fast Shrink-and-Check Protocol (FSCA) 13
3.5 Solution 3 : Push-and-Pull Forces Protocol (PAP) 15

4 Performance Evaluation 19
4.1 Number of message transmissions 20
4.2 Number of iterations (slots) 21
4.3 Standard deviation of DC ranges 23

5 Conclusions 25

Bibliography 27

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