適用於無線微型感測網路低延遲且低耗電之媒體存取控制協定

Abstract

無線微型感測網路是由一群具備極有限電力的無線微型感測器所組成，此種網路的目的是收集目標區域的特定資料，並將其回傳到基地台供管理者監測及控管。對無線微型感測網路來說，節省能源消耗以及縮短資料傳輸延遲是兩個非常重要的課題。在許多已完成的研究報告裡顯示傳輸資料是最為耗電的一個動作，天線模組是最耗電的元件，由於天線模組的動作被媒體存取協定控制，此提供了我們一個研究的切入點。本篇論文提出了一個同時能節省能源消耗並縮短資料傳輸延遲的媒體存取控制協定，現有宣稱能達到省電效果的媒體存取控制協定皆讓整個感測網路的感測器遵守同一個動作排程，所有的感測器會在同一時間將天線模組開啟並進行傳送資料的動作，在一段時間後同時將天線模組關閉以達到省電效果，此排程會讓所有感測器週而復始做此動作。雖然使用此排程的媒體存取控制協定的確可以達到省電的效果，但同時卻造成很嚴重的資料傳輸延遲。本篇論文所提出的媒體存取控制協定不要求所有感測器皆遵守同一排程，而是根據各個感測器的所在位置安排其獨有的排程，這個設計可以有效的減少資料傳輸延遲。除此之外為了讓我們提出的協定能適用於各種不同的網路流量及網路類型，我們提供了一個可將感測器排程使用的更靈活的機制，撘配此機制使用可達到最好的省電以及縮短傳輸延遲的效果。

Wireless Sensor Networks (WSNs) are formed by a set of small devices with limited battery capacity, which collect sensed data and transmit it to the base station. Energy conservation and data transmission latency are considered two important issues. Among all operations, data transmission dominates the consumption of energy. In this thesis, we proposed a MAC protocol which can significantly reduce energy consumption and transmission latency. The existing MAC protocols use a unique periodical active/sleep schedule for the whole network to save energy. However, these protocols suffer long transmission latency. Rather than unifying the periodical active/sleep schedule of all sensor devices, we arrange the schedule of each sensor device according to its location on the data gathering tree. This arrangement can provide continuous data forwarding through active sensor devices. The energy consumption is also conserved during the periodical sleeping periods. To dynamically adapt to different traffic load, an adaptive sleeping scheme is proposed, which adjusts the active/sleeping schedule of each sensor device according to the traffic load. The simulation showed that the proposed MAC protocol obtains significant energy saving and reduces transmission latency.