Distributed Rate-Loss Based Channel Assignment in Multi-Rate Wireless Mesh Networks

無線網狀網路(Wireless Mesh Networks)提供了較划算的寬頻上網方案，而多重頻道多重網卡(Multi-Channel Multi-Radio)無線網狀網路為近年來重要的研究領域之一，如何利用多重頻道多重網卡來使得整個網路的效能增加，近年來已受到許多關注。之前大多數關於頻道配置的研究都假設所有鏈結均使用基礎速率(basic rate)作傳輸，並沒有考慮到多重傳輸速率(multiple bit-rates)的使用。然而，在多重傳輸速率網路中，當高傳輸速率的鏈結和低傳輸速率的鏈共享相同的頻道時，高傳輸速率的鏈結可達到的吞吐量會受到低傳輸速率的鏈結影響而大幅地降低，此問題被稱為多重速率分享問題(Multi-rate sharing problem)。了解決此問題，我們提出了一個基於速率損失之分散式頻道配置演算法(Distributed Rate-Loss Based Channel Assignment)，可以有效的減輕多重速率分享問題。我們也提出了一個速率損失函數來幫助進行頻道配置，藉由速率損失值來表示當鏈結使用某頻道時，對整體網路的速率所造成之損失。電腦模擬的結果顯示我們的頻道配置方式勝過現在的方法許多，並且適用於不穩定的環境中。Wireless Mesh Networks(WMNs) provide cost-effective broadband access for users. Multi-Channel Multi-Radio Wireless Mesh Networks has been one of the most important research topic. In WMNs, much attention has been paid to the problem that how to efficiently utilize multiple orthogonal channels and multiple communication radios to enhance the aggregate throughput. Most of prior works on the channel assignment problem assume that all transmission links use the basic rate and do not consider the presence of multiple bit-rates. However, in multi-rate wireless net-orks, the achievable throughput of high-rate links is severely affected by low-rate links when they share the same physical channel. This problem is called multi-rateharing problem. o address the problem, we proposed a Distributed Rate-Loss Based Channel Assignment, which can efficiently alleviate the multi-rate sharing problem. We also proposed a Rate-Loss function to support our channel assignment, where the Rate-Loss value represents the total rate degradation of all links using the channel when the current link chooses this channel. The simulation results shows that our algorithm outperforms existing schemes and is suitable for unstable environment.Abstract (in Chinese) . . . . . . . . . . . . . . . . . . . . . . . . . . . iibstract (in English) . . . . . . . . . . . . . . . . . . . . . . . . . . . . iiiable of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vist of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiist of Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiiist of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiihapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Problem Definition and Contributions . . . . . . . . . . . . . . . . . 4.4 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . 5hapter 2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Multi-Channel Multi-Radio WMNs . . . . . . . . . . . . . . . . . . . 6.1.1 Channel Assignment in WMNs . . . . . . . . . . . . . . . . . 6.1.2 Joint Routing and Channel Assignment in WMNs . . . . . . . 7.2 Multi-rate Wireless Networks . . . . . . . . . . . . . . . . . . . . . . 8.2.1 Automatic bit-rate selection algorithm . . . . . . . . . . . . . 8.2.2 Multi-rate Sharing Problem . . . . . . . . . . . . . . . . . . . 9hapter 3 Rate-Loss Based Channel Assignment . . . . . . . . . . 10.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Rate-Loss Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Channel Assignment Algorithm . . . . . . . . . . . . . . . . . . . . . 16hapter 4 Performance Evaluation . . . . . . . . . . . . . . . . . . . 19.1 Throughput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 Resilience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24hapter 5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 26ibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2