無線網狀區域網路是由一些支援網狀服務(mesh service)的節點所組成的通訊網路。由於具有隨意網路(ad hoc network)的特性，因此能夠讓傳輸範圍內的節點在不透過存取點(access point, AP)的情況下互相通訊，藉由此特性，我們能用較低的成本來建置較大覆蓋範圍的網路。由於目前IEEE 802.11 a/b/g皆採用碰撞避免式載波偵測多重存取(carrier sense multiple access with collision avoidance, CSMA/CA)機制，在網狀網路架構下將會大幅增加碰撞機率，因此IEEE802.11s草案中，除了導入網狀網路架構外，亦加入以預約為基礎的存取機制，稱為MDA(mesh deterministic access)。MDA能讓節點以較少的競爭與碰撞來進行媒體存取，但只能工作於單通道環境，造成網路流量無法提升。

為了解決上述問題，本論文在網狀網路架構下，將MDA機制加以改善，提出一個多通道存取機制。我們將DTIM(delivery traffic indication map)區間切割為競爭區間與傳輸區間，配合四向交握(four-way handshake)機制及本論文所提出的NMST(neighbor MP status table)，能夠使節點更有效地利用通道空間，並避免資訊錯誤可能產生的碰撞情形。從模擬結果可知，與以競爭為基礎的EDCA(enhanced distributed channel access)相比，本論文提出的機制可有效提升整體網路效能。

A wireless mesh LAN is a communications network made up of radio nodes that support mesh service. It combines the feature of ad hoc network, so nodes can communicate with other nodes directly without access point (AP). According to this feature, we can deploy network with larger coverage and lower cost. Because all based on carrier sense multiple access with collision avoidance (CSMA/CA) base to IEEE 802.11 a/b/g wireless system at present, the collision probability will be much higher if we use the scheme in wireless mesh LAN. In IEEE 802.11s draft, not only the mesh network topology be introduced, but also a new reservation based MAC access scheme, MDA, be introduced. Nodes that support MDA can access wireless medium with lower collision probability, but it can just work in single channel, so the capacity of network is limited.

In order to solve the above-mentioned problem, we proposed a new multi-channel access scheme that improved from MDA. We divide the mesh DTIM (delivery traffic indication map) interval into two fields, contention field and transmission field. To operate in coordination with four-way handshake and proposed NMST (neighbor MP status table), nodes can access channels more efficiently, and to avoid collisions with wrong information from other nodes. The simulation results show that the proposed scheme improves the network throughput over collision based scheme, i.e., EDCA.

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