IEEE 802.11 是目前在無線通訊網路中被廣為使用的技術，其主要運作在single channel的環境。然而，multi-channel 的通訊環境不僅可以將使用者分散在不同的channel，可避免因過度競爭而使throughput 下降，亦可讓不同的使用者即使在狹小的環境中，也能在同一時間以不同的channel 通訊。因此，可以避開同channel 的干擾並有效提升整體throughput，縮短等待時間並達到頻寬利用最大化。 在本論文中，我們考慮在802.11無線網路環境下，以multi-channel MAC Protocol(MMAC Protocol)為基礎，提出Enhance of multi-channel MAC protocol，以解決因靠ATIM window控制訊息，而造成效能瓶頸、以及頻繁切換頻道的問題。我們所提出的協定具有等待時間縮短、盡量避免衝撞及維持公平性等特色，我們並透過實驗顯示本協定在擁塞的網路環境中，具有延遲時間短、頻寬利用率高以及有較高的網路吞吐量等優點。 IEEE 802.11 is popularly used in Wireless Communication Network, and it works on single-channel environment. However, multi-channel environment not only lets users distribute in different channels avoiding from throughput reduction due to contentions, but also makes different users communicate with each other in narrow environment at the same time even if they on the different channel. Thus, it can avoid interference in the same channel and make performance enhancement for throughput. Moreover, it decreases waiting time and makes the usage of maximally utilized bandwidth. In this Paper, we propose Enhancement of multi-channel MAC protocol in 802.11 wireless networks. This method is based on multi-channel MAC Protocol for solving the bottleneck of throughput and the problem of switching channel frequently due to the overhead by sending control messages through ATIM window. The features of our proposed protocol are short waiting time, avoiding from collisions as much as possible, and maintaining its fairness during channel selection. Besides, our simulation results show that the proposed scheme can reduce delay time, enhance the usage of bandwidth and reach higher throughput for Enhance of multi-channel MAC protocol.
