802.16無線網狀網路下之頻寬分析

Capacity Analysis in 802.16 Wireless Mesh Network

李冠群(Kuan-Chun Lee)

指導教授 ： 鍾添曜

元智大學/資訊學院/資訊工程學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00295

摘要

本論文探討802.16無線網狀網路之下的網間流量頻寬(inter-flow capacity)問題。首先，我們將頻寬問題轉化成找出最小排程週期的問題。再來，我們著重於擁有均勻流量和隨機分布拓撲的802.16無線網狀網路。我們先定義碰撞區域(collision area)，在此區域中所有連接都無法同時傳送。因此，瓶頸碰撞區域限制了排程的週期。在不同的MAC實作可能導致不同的瓶頸碰撞區域，因此我們先假設使用混合模式，也就是上行資料和下行資料可能可以同時傳輸，再分別找出對稱性MAC和非對稱性MAC的最小重用距離。計算出瓶頸碰撞區域的資料量後，我們也得到了代表頻寬的公式。最後，我們希望上述分析的啟發可用於任何無線網狀網路，因此發展了瓶頸優先時槽指派(Bottleneck First Slots Assignment, BFSA) 演算法。為了簡化計畫複雜度，此演算法使用鏈結上的干擾資料量作為選擇排程順序的依據。
從模擬和分析結果可看出，分析出來的頻寬比過去的研究更好，還有在網間流量之下，傳輸範圍及頻寬的關係和網內流量(intra-flow)是相反的。在對稱式MAC之下，BFSA演算法非常接近最佳的排程演算法，即使在非對稱性MAC之下，它還是表現的不錯。

關鍵字

頻寬分析 ； 排程演算法 ； 無線網狀網路 ； 802.16 ； WiMax ； 網間流

並列摘要

This thesis studies the inter-flow capacity problem in 802.16 WMNs. First, we characterize the capacity problem as the problem of finding the minimum period of slot schedules. Then, we consider the capacity in 802.16 WMNs with a uniform traffic pattern and random topology. Based on the concept of global scheduling, we define a collision area in which no links can transmit simultaneously. According to characterization of 802.16 MAC, the coverage of a collision area is derived for asymmetric MAC and symmetric MAC by employing the concept of minimum reuse distance. Following that, the bottleneck collision area of a 802.16 network and its traffic load are identified. Finally we obtain a close-form expression of inter-flow capacity assuming that downlink and uplink flows can transmit concurrently. To extend our analysis to 802.16 networks with arbitrary topology, the finding of analysis is used to develop a Bottleneck First Slot Assignment (BFSA) algorithm for WMNs.
Through simulations and numerical analysis, it is shown that the proposed analysis can better estimate the inter-flow capacity than that of previous research. The results also illustrate that the relationship between the transmission range and the inter-flow capacity is opposite to the intra-flow capacity. And, the BFSA algorithm performs close to optimal with the symmetric MAC, while it performs well with the asymmetric MAC.

並列關鍵字

capacity analysis ； scheduling algorithm ； wireless mesh network ； 802.16 ； WiMax ； inter-flow

參考文獻

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[2] IEEE Std. 802.11, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification,” 1999.

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