非飽和狀態下IEEE 802.11多跳無線網路延遲表現之探討

Abstract

媒體存取延遲是無線網路運作效能很重要的一個指標。在本篇論文中，我們提供一個IEEE 802.11多跳無線網路環境，背景傳輸於非飽和狀態下，媒體存取延遲的模型。藉由此一模型，我們不僅能提供平均延遲，還能提供延遲的變異數、以及其機率分佈。在我們提出的模型中，我們考慮了許多無線網路中的參數，包 括802.11通訊協定的設計、隱藏終端點問題、以及無線節點的空間分佈。除此之外，我們提供了一個以簡單的統計數據來判別802.11無線網路飽和狀態的方式，以及討論此一飽和狀態對於分析準確度的影響。在模擬數據中我們可以看到，藉由我們所提出的模型，當網路狀態符合非飽和的條件時，我們可以準確的預測媒體存取延遲的機率分佈。

Media access delay is an important performance measurement in wireless networks. In this thesis, we provide a model of the media access delay in IEEE 802.11 multi-hop wireless networks under unsaturated background traffic. With this model, we are able to provide not only the average delay, but also the variance and probability distribution of this delay. In our model, we considered various variables in network performance, including 802.11 protocol design, hidden terminal problem, and topology of the wireless nodes. In addition, we provide a simple statistical measurement to identify the state of saturation in 802.11 wireless networks, and how this state effect on the accuracy of the analysis. In the simulation, we can see that this model will result in an accurate estimation of delay distribution when the requirements of an unsaturated network are met.