廖婉君臺灣大學：電機工程學研究所黃慶齡Huang, Ching-LingChing-LingHuang2007-11-262018-07-062007-11-262018-07-062004http://ntur.lib.ntu.edu.tw//handle/246246/53418無線區域網路已經成為今日家用網路的一部分，上面執行了各式各樣的應用,例如：遠端遙控，安全閉路攝影機，隨選視訊，網路電話，串流影音，還有網際網路的存取。同時網路服務業者也使用無線區域網路來架設社區網路，或用其來彌補第三代行動寬頻的不足。隨之而來，將有激增的多媒體應用程式會被使用在無線區域網路上，這項趨勢會帶來新的挑戰，也就是這些應用對網路的品質服務要求。所謂的品質服務指的是網路有能力針對不同的等級的流量，提供不同等級的通訊品質。衡量品質服務重要的指標有幾個：延遲和延遲變異。俗稱的頻寬是指資料傳輸的容量，也會影響單位時間的傳輸量，也就是資料吞吐量。端點到端點的延遲是指封包從網路的傳送端到接收端花的時間，而網路存取的延遲則是指從封包抵達傳送端，到封包成功被傳送出去所花的時間。延遲變異通常被定義為延遲的標準差或是變異量，它對網路多媒體程式的撥放或是網路電話特別重要。然而，現今主流的無線區域網路協定IEEE 802.11對品質服務的支援仍然有限，有鑑於此，目前有一個正在發展中的協定IEEE 802.11e，它是原來IEEE 802.11的延伸協定，其中提供了分散式的無線通道存取方式: EDCA，他是原來802.11中DCF功能的延伸。這篇論文就是要分析這個協定的效能，同時也用NS-2模擬程式來驗證分析結果的正確性，模擬結果證明分析的結果十分符合模擬程式的結果，也因此提供了一個良好的模型來描述IEEE 802.11e的行為。Today, WLANs are being used in residential networks to support a wide range of applications such as remote controls, video from a security camera, delivery of video on demand, voice telephony, streaming audio, and Internet access. WLANs are also being used in community networks and as a low-cost replacement for 3G broadband services by service providers. As a result, more and more multimedia applications such as voice telephony and video streaming bring challenging quality of service requirements to WLANs. Quality of service (QoS) refers to the ability of a network to provide some consistent level of ensuring data delivery over the network with different levels for different classes of traffic. Important QoS metrics for multimedia applications are throughput, delay, and jitter. Throughput is the amount of data successfully transmitted and received in unit time. End-to-end delay is the time between the arrival of a packet and its successful delivery to the receiver. Access delay is the time between packet arrival and packet transmission by the sender. Jitter is the standard deviation or variation of delay and is an important metric for multimedia applications, such as Voice over IP (VoIP). IEEE 802.11 is currently the dominant protocol for WLANs. However, there is only limited QoS supporting mechanism in IEEE 802.11. IEEE 802.11e Medium Access Control (MAC) is an emerging supplementary standard to support QoS for IEEE 802.11. The Enhanced Distributed Channel Access (EDCA) in 802.11e is an enhanced version of legacy DCF, and provides contention-based differentiated channel access for frames with different priorities. In this thesis, the behavior of each station providing EDCA for IEEE 802.11e WLANs is analyzed, in terms of the throughput, delay, and jitter. Simulations are running in NS-2 simulator to verify this analytical model. The results show that analytical results match the simulation results very well, thus providing a good description for the EDCA of IEEE 802.11e systems.Chapter 1 Introduction 1 1.1. Limited QoS Supported by IEEE 802.11 2 1.2. Various QoS Mechanisms Proposed for 802.11 6 1.3. Enhanced Distributed Channel Access in IEEE 802.11e 8 1.4. Motivation and Related Work 11 1.5. Thesis Organization 12 Chapter 2 Analysis of IEEE 802.11e 13 2.1 EDCA Throughput Analysis 13 2.2 EDCA Delay and Jitter Analysis 25 Chapter 3 Simulation Verification 33 3.1 Simulation Scenario I 36 3.1.1 Basic mode performenace 37 3.1.2 RTS/CTS mode performance 43 3.2 Simulation Scenario II 49 3.2.1 Basic mode performance 50 3.2.2 RTS/CTS mode performance 56 Chapter 4 Concluding Remarks 62 Reference 63757763 bytesapplication/pdfen-US品質服務無線區域網路Wireless LANQuality of Servicethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/53418/1/ntu-93-R91921073-1.pdf