IEEE802.11s 草案中提出一種新的媒體存取控制(MAC)存取功能-MDA (mesh deterministic access)，主要用於單通道的無線網狀區域網路。但在單通道環境中容易發生控制封包與資料封包之碰撞和網路容量不足的問題。為了能提供無線網狀區域網路更高的網路容量和效能，本論文希望將MDA機制的運作拓展至多通道網路架構。而為了減少硬體設計時的硬體資源需求和設計複雜度，我們只允許無線網狀區域網路內的網狀節點裝備單一的傳收器來支援多通道環境。首先將網狀DTIM (delivery traffic indication message)間隔分割成競爭區間和資料傳輸區間，完全避免控制封包和資料封包發生碰撞。並新定義鄰近網狀節點狀態表格(NMST)使得網狀節點能支援多通道環境。競爭建立MDAOP (MDA opportunity)的機制採用四向交握模式，以期有效降低隱藏節點的問題。在選取MDAOP機制方面則新設計CLFRF (channel load first random fit)和MCBF (multi-channel best fit)兩種機制來幫助網狀節點選取MDAOP時更有效率。本論文所提出的多通道 MDA (MMDA)演算法可以充分使用多通道環境以達到提升無線網狀區域網路的整體效能。模擬結果清楚呈現不論網路處於飽和或非飽和模式，MMDA演算法在產能、平均等待時間和封包丟棄率都比EDCA (enhanced distributed channel access)表現為佳。
不過當無線網狀區域網路處於高負載的狀態下，因MMDA演算法採用固定配制競爭區間的機制，故會遭遇網路資源浪費的問題。為了解決此問題，本論文另提出動態調整競爭區間(DACP)的機制。此外尚採用ABP (adaptive backoff process)來改良MMDA演算法的公平性。在模擬結果方面，我們所提出的方法在無線網狀區域網路重載時效能表現較MMDA演算法和EDCA更好。

IEEE802.11s draft proposes a new medium access control (MAC) function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). In single-channel environment, collisions between control packets and data packets may occur very often. In order to provide higher network capacity and performance for wireless mesh LAN, this thesis develops an algorithm for MDA to work well on multi-channel wireless mesh LAN. To reduce the hardware requirements in design, a mesh point (MP) only equips single transceiver to support multi-channel environment. To completely avoid the collision between control packets and data packets, the mesh delivery traffic indication message (DTIM) interval is first divided into contention period (CP) and data transmission period (DTP). We newly define a neighbor MP status table (NMST) for MPs to support multi-channel environment. The mechanism of reserving MDA opportunity (MDAOP) adopts the four-way-handshaking mode to reduce hidden node problem; we propose channel load first random fit (CLFRF) and multi-channel best fit (MCBF) mechanisms to select MDAOP. This thesis proposes a multi-channel MDA (MMDA) algorithm to improve the overall performance of wireless mesh LAN in multi-channel environment. The theoretical analysis gives the upper limit of the throughput for MMDA algorithm. The simulation experiments clearly show the results in multi-channel wireless mesh LAN environment that MMDA algorithm performs better than enhanced distributed channel access (EDCA) in throughput, average waiting time, and packet drop ratio both in the saturated and non-saturated mode.
But MMDA algorithm suffers the resource waste problem by used fixed CP ratio when wireless mesh LAN is at heavy loading situation, so this thesis also proposes a dynamic adjustable contention period (DACP) mechanism to solve this problem. In addition, we also adopt a adaptive backoff process (ABP) to improve the fairness of MMDA algorithm. The simulation experiments show the results in heavy loading multi-channel wireless mesh LAN environment that the proposed scheme performs better than MMDA algorithm and EDCA in throughput, average waiting time, and packet drop ratio.

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