行動隨意網路下隱藏接收節點問題之研究

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Title:	行動隨意網路下隱藏接收節點問題之研究
Other Titles:	A Study on Hidden Receiver Problem in Mobile Ad Hoc Networks
Authors:	羅群智 Lo, Chun-Chih
Contributors:	朱延平 Chu, Yen-Ping 東海大學資訊工程學系
Keywords:	隨意網路,隱藏節點問題,二元指?倒退法 Ad Hoc Network, Hidden Terminal Problem, Binary exponential backoff
Date:	2008
Issue Date:	2011-03-23T05:56:18Z (UTC)
Abstract:	媒體存取協定（Medium Access Control, MAC）在IEEE 802.11的標準中，一直都是無線區域網路（Wireless Local Area Networks, WLAN）與無線行動隨意網路（Mobile Ad Hoc Networks, MANET）的標準。所謂的Hidden Receiver的問題是由於高度忽視隱藏節點的存在而讓潛在的傳送者（隱藏節點的鄰居）進入了一個不必要的退避過程(Backoff)和重傳循環，所以導致競爭者之間嚴重的不公平競爭並增加了封包碰撞(Collision)與干擾(Interference)的可能性。因此，大大的降低網路吞吐(Throughput)的表現，這也讓Hidden Receiver成為無線行動隨意網路最值得探討的議題。在這一篇論文裡，我們探討了在無線網?環境下所存在的相關問題，並且提出了兩個可以應用在IEEE 802.11 Distributed Coordination Function (DCF)與 Explicit Blocking Notification (EBN)的改善方法。模擬結果顯示我們所提出的方法?但可以有效?低封包碰撞的機?，且可減少網?媒介的競爭以及有效的提升網路公平性，更可以大大的改善網?整體的吞吐?(System Throughput)與品質的服務(QoS)。 In IEEE 802.11 Medium Access Control (MAC) protocol has been the standard for the Wireless Local Area Networks (WLAN) and Mobile Ad Hoc Networks (MANET). However, the hidden receiver problem is the primary concern in wireless ad hoc networks, due to the high rates of neglecting the state of the hidden terminal; the potential sender (neighbors of the hidden terminal) enters into an unnecessary backoff process and retransmission circle, therefore leading to serious unfairness between contention terminals.Hidden receiver problem increases the probability of collision and interference, hence, degrading the performance of network throughput significantly. In this thesis, we review the related problems in wireless environments and proposed two improved schemes with an additional procedure which can be adapted to IEEE 802.11 Distributed Coordination Function (DCF) and Explicit Blocking Notification (EBN) schemes. Our simulation results have shown that our proposed schemes not only achieve better fairness between competing traffics, reducing the probability of collisions and decreasing the contention on medium access but also greatly improve system throughput and the Quality of Service (Qos) of networks.
Appears in Collections:	[Department of Computer Science and Information ] Master's Theses

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