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研究生:王修安
研究生(外文):Xiu-An, Wang
論文名稱:ㄧ個無線網路的免競爭CSMA媒體存取控制協定
論文名稱(外文):A Contention-Free CSMA MAC Protocol for Wireless Networks
指導教授:郭耀文郭耀文引用關係
指導教授(外文):Yaw-Wen, Kuo
口試委員:溫志煜黃建華
口試委員(外文):Zhi-Yu, WenJian-Hua, Haung
口試日期:2011-07-20
學位類別:碩士
校院名稱:國立暨南國際大學
系所名稱:電機工程學系
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2011
畢業學年度:99
語文別:中文
論文頁數:63
中文關鍵詞:無線網路媒體存取控制層載波偵測多重存取服務品質保證
外文關鍵詞:wireless networksMACCSMAQoS
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在傳統的無線區域網路中,採用CSMA/CA協定,當節點從上層接收到封包要傳送前,必須感測現在的通道是否是空閒狀態,若通道為是在空閒狀態,則從Contention Window(CW)中隨機選取一個值作為倒數時間,數到零才能傳送封包。當網路中節點變多,多個節點同時數到零的機率就會上升,使得封包碰撞的機率也跟著上升,造成封包延遲時間變大以及吞吐量下降的狀況。在這篇論文中,我們為了消除無線區域網路中的封包碰撞所造成的效能下降,基於CSMA機制上提出了一個基於基礎架構模式下的新媒體存取協定,命名為免競爭的排程協定(CF-CSMA)。在CF-CSMA機制中,每個網路使用者使用通道的次序將由基地台(AP)來管理與控制,如此一來發生封包碰撞的情況將可完全避免,因此可以有效地降低延遲時間及提升吞吐量。除了提出新的排程協定之外,我們使用NS2來創建模型,並模擬實際網路狀況進行分析。模擬結果證明我們提出的機制在封包延遲、碰撞機率以及平均網路傳輸流量,這幾個項目中遠優於傳統的協定。
The CSMA/CA protocol is commonly used in many wireless networks. When a station receives a packet from its upper layer, it has to sense the channel before transmission. If the channel is idle, it randomly chooses a value according to its current Contention Window as its backoff counter and starts the backoff procedure. When it counts down to zero, the station starts transmission. As the number of nodes increases, the probability that more than one station transmits increases, results in high collision probability and performance degradation. To solve the problem, we propose a new medium assess protocol named contention-free (CF-CSMA) for the infrastructure mode of wireless LANs. In the CF-CSMA scheme, all stations use the channel sequentially according to the order controlled by the Access Point (AP) and packet collision can be totally eliminated. In addition, we implement the CF-CSMA scheme in NS2 to simulate the real networks. Simulation results show that the proposed scheme outperforms traditional schemes in terms of packet delay, collision probability and throughput.
第一章 序論..........................................................................................................................1
1.1 前言.........................................................................................................................1
1.2 研究動機與目的.....................................................................................................2
1.3 論文簡述.................................................................................................................3
第二章 背景知識..................................................................................................................4
2.1 基礎架構模式網路.................................................................................................4
2.2 隨意無線模式網路.................................................................................................6
2.3 IEEE 802.11 MAC 介紹......................................................................................6
2.3.1 載波偵測多重存取/碰撞避免(CSMA/CA) ...............................................7
2.3.2 二元指數後退演算法(BEB)機制介紹.......................................................7
2.3.3 分散式協調功能(DCF) ..............................................................................8
2.3.4 RTS/CTS Scheme.....................................................................................10
2.3.5 分散式協調功能的問題............................................................................12
2.3.6 中樞協調功能(PCF) .................................................................................13
2.4 工作站如何加入一個無線網路...........................................................................14
2.4.1 信號彈(Beacon) ........................................................................................14
2.4.2 被動式掃描(Passive Scanning) ................................................................17
2.4.3 主動式掃描(Active Scanning) .................................................................17
2.4.4 開放系統式驗證(Open system) ................................................................18
2.4.5 共享密匙式驗證(Shared Key) ..................................................................19
2.5 固定競爭視窗機制介紹.......................................................................................21
2.6 延後競爭分散式協調功能介紹...........................................................................22
第三章 提出的方法............................................................................................................23
3.1 CF-CSMA..............................................................................................................24
3.1.1 CF-CSMA運作方式..................................................................................24
3.1.2 工作站如何加入無線網路........................................................................28
3.1.3 週期的更新................................................................................................29
3.2 CF-CSMA機制效能的估測.................................................................................34
3.2.1 最大吞吐量(throughput)的計算................................................................34
3.2.2 封包延遲時間的估測................................................................................36
3.2.3 佇列時間的估測........................................................................................37
3.3 DCF機制效能的估測...........................................................................................38
第四章 模擬結果與分析....................................................................................................41
4.1 模擬環境與參數設定...........................................................................................41
4.2 模擬結果...............................................................................................................44
4.2.1 固定流量環境............................................................................................44
4.2.2 多種資料流量環境....................................................................................49
第五章 結論........................................................................................................................59
Reference.............................................................................................................................61

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[5].IEEE 802.11n, “IEEE Standard for Information technology - Telecommunications and information exchange between systems – Local and metropolitan area networks – Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 5: Enhancements for Higher Throughput”, 2009.
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[7].IEEE 802.11d, “IEEE Standard for Information technology - Telecommunications and information exchange between systems – Local and metropolitan area networks – Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 3: Specifications for Operation in Additional Regulatory Domains, 2001.
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[21].“MPEG-4 and H.263 Video Traces for Network Performance Evaluation”, http://www-tkn.ee.tu-berlin.de/research/trace/trace.html
[22].S. Siwamogsatham, “On Backoff Timer Scheduling for Smart-DCF and Performance Evaluation”, IEEE Advanced Information Networking and Applications – Workshops, pp.1278-1284, March 2008.
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[25].NS2 Learning Guide, http://140.116.72.80/~smallko/ns2/ns2.htm

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