次世代無線網狀網路最佳化設計

Abstract

早期在無線網狀網路這方面的研究工作大多數都是假設每一個節點都只有單一的介面。在此份論文中，我們視下一代的無線網狀網路為每個節點都有著多重的無線電介面，每個介面都有能力支援多重模式並且執行一種，支援多重通道並使用其中一個，而且有能力支援多重的調變技術，我們把這種網路叫做 M^4（多重無線電，多重模式，多通道，多重速率）無線網狀網路。舉例來說，使用現成的零組件，人們可以輕易的建構一個有著多重無線電介面（支援IEEE 802.11 a/b/g）網狀網路的節點，我們的目標就是去處理在這樣一個環境中的資源分配規劃以及封包傳送的問題。 我們提出的方法是建立在以網路流量原則以及無線電通道 存取/干擾 模型為前提的線性規劃技術基礎上，當給定一個網路拓樸，運輸量的需求，以及閘道的容量，我們展示了如何去分派網路介面卡數目以及他們所使用的通道以便可以充分的使用整個頻寬。這些結果可以讓無線網路的提供者在硬體層面的限制下可以利用以上的方法來分配計畫他們的網路以達到最大的收益效率。這份論文最值得一提的就是，這是在無線網狀網路領域中第一份去處理資源計畫的工作。我們的一些數據上的結果顯示了在不影響網路層公平性下的網路總和流量有著大量顯著的改進。與其他假設固定無線電介面數量的多重無線電系統在模擬上的比較也進一步證實了網路規劃的重要性。

Most earlier works in the area of wireless mesh network assume a single interface being equipped in each node. In this thesis, we consider the next-generation wireless mesh networks in which each node may be equipped with multiple radio interfaces, each capable of running in one of several modes(IEEE 802.11 b/g 2.4GHz or 802.11a 5GHz mode), one of several channels,and each capable of supporting multiple modulations. We call such a network an M^4 (multi-radio, multi-mode, multi-channel, multi-rate) wireless mesh network. For example, from off-the-shelf components, one can easily construct a mesh node with multiple IEEE 802.11a/b/g radio interfaces. Our goal is to address the resource planning and packet forwarding issues in such an environment. The proposed methodology is based on linear programming with network flow principles and radio channel access/ interference models. Given a network topology, traffic requirements, and gateway capacities, we show how to allocate network interface cards and their channels to fully utilize channel bandwidths. The results can be utilized by a wireless Internet service provider to plan their networks under a hardware constraint so as tomaximize their profits. To the best of our knowledge, this is the first work addressing resource planning in a wireless mesh network. Our numerical results show significant improvement in terms of aggregate network throughput with moderate network-layer fairness. The importance of network planning is further corroborated by the simulative comparisons with other multi-radio systems assuming a known and fixed number of interfaces at each mesh router.