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研究生:劉昆宗
研究生(外文):Kun-tsung Liu
論文名稱:車載網路通道協調機制之研究
論文名稱(外文):A Study on Vehicular Network Channel Coordination
指導教授:江季翰江季翰引用關係紀光輝
指導教授(外文):Ji-han JiangKuang-hui Chi
學位類別:碩士
校院名稱:國立雲林科技大學
系所名稱:電機工程系碩士班
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:2009
畢業學年度:97
語文別:中文
論文頁數:55
中文關鍵詞:車載網路通道協調
外文關鍵詞:Vehicular NetworkChannel Coordination
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本論文所關心的是車載隨意網路(Vehicular Ad-Hoc Network, VANET)上頻道切換(Channel Switch)的議題。在多頻道的通訊環境中,單一收發器(transceiver)無法在同一時間收發每個頻道的訊息。利用頻道切換機制,可以使收發器在不同的頻道之間作切換,讓行駛中的車輛能在不同頻道遞送安全性訊息或非安全性訊息,以達到公共安全與資訊服務等目的。目前已有數篇關於頻道切換機制的文獻被提出,雖然這些機制在某些方面有其優勢,但各自仍有其待改進之缺點,諸如頻道浪費、不符合標準規定等。
鑑於上述的缺點,本論文提出一個適應性頻道協調(Adaptive Channel Coordination, ACC)的演算法,並結合車載通訊中群集式(cluster-based)多頻道控制操作,希望能建立一個減少頻道資源浪費,增進頻道效率的頻道切換協定。ACC演算法的設計理念是利用IEEE 802.11e所制定的EDCA (Enhanced Distributed Channel Access)機制,將訊務(traffic)針對其特性分成四種存取種類,每一種類各自有不同的競爭參數。ACC演算法便是根據每個封包不同的競爭參數,來預測接下來的時間週期內,哪些封包能脫穎而出,接著依據這些封包的種類來分配控制頻道和服務頻道的時間比例。而ACC演算法結合群集式多頻道控制操作的原因在於,讓群集首(Cluster Head)執行ACC演算法以便於統合整個群集的頻道切換時間。然而模擬結果顯示,我們提出的方法雖然增加了通訊頻道的使用率,執行效益卻不如預期。歸納出來的原因有三。首先,群集式通訊架構易於增加控制訊息的交換,因此頻道使用度雖較高,但對資料封包的傳輸並未有顯著改善。其次,群集首的下行(downlink)訊務無法完全代表群集中,其他車輛之間上行(uplink)訊務的分配比例,這意味著群集首的訊務分配比重為關鍵所在。最後,ACC演算法的計算量隨封包數量增加而負擔變大。因此未來將著重在ACC演算法的改良,並加強群集式多頻道控制協定的架構設計,以期能對車載隨意網路提供可實際應用的協定設計。
This thesis is concerned with channel switching in vehicular ad hoc networks. In a multi-channel communication environment, a single transceiver cannot send and receive information over different channels at the same time. As a remedy, the introduction of a channel switching mechanism enables the transceiver to exploit different channels to deliver public safety or security information during car driving. As far as channel switching mechanisms are concerned, a number of schemes have been proposed in the literature. Though effective in some aspects, these schemes suffer certain drawbacks, such as wasting channel time, resulting in low utilization, and being incompatible with the standard.
In view of such deficiency, we present an adaptive channel coordination algorithm (ACC) that is incorporated in cluster-based multi-channel control operations for vehicular communication. Our objective is to develop an efficient channel-switching protocol so as to reduce the waste of channel resources or better utilize radio links for data transmission. Our ACC algorithm is designed in line with IEEE 802.11e EDCA (Enhanced Distributed Channel Access) machinery. In EDCA, traffic is classified into four access categories according to its characteristics and every category is associated with different parameters for channel contention. Our ACC algorithm is performed by each cluster head that predicts which downlink packets in its transmit queues are more likely to gain access to radio channels over the next period of time. Assuming a certain number of such packets to be delivered during the time frame, we then determine what proportion of time should be allocated to Control Channel and Service Channel, respectively, according to the access categories of these packages. Our ACC algorithm designates each cluster head to intermediate in this fashion in that the cluster head knowledgeable of traffic conditions within its cluster can plan channel switching time somehow. Simulation results, however, show that the proposed scheme does not perform fully to our expectations, although radio channels have appeared to be better utilized in our architecture. This results from three main causes. First, a cluster-based communication architecture tends to demand more control message exchanges, accounting for higher channel utilization as compared with other counterpart schemes. Second, downlink traffic at the cluster head cannot equally reflect uplink traffic distribution among vehicles in the cluster, implying that the presumed allocation of channel time by a cluster head is susceptible to some errors of estimation. Third, our ACC algorithm is liable to become computationally intractable when quantities of packets arrive. Aware of performance deficits in our design, we shall work toward improving our ACC algorithm and strengthening the cluster-based network paradigm, such as to eventually result in a practical means for vehicular communication.
摘要 i
Abstract ii
誌謝 iv
目錄 v
表目錄 vii
圖目錄 viii
第一章 序論 1
1.1 前言 1
1.2 研究動機 1
1.3 論文架構 2
第二章 背景知識 3
2.1 DSRC (Dedicated Short Range Communication)簡介 3
2.2 EDCA (Enhanced Distributed Channel Access)簡介 7
2.2.1訊務區別 7
2.2.2 EDCA緩衝器的參數資訊 9
2.2.3 改良後的EDCA機制 10
第三章 文獻探討 12
3.1 Channel-Switch機制 12
3.1.1 Global Synchronization簡介 12
3.1.2 i-Channel簡介 13
3.1.3 Independent Channel Switching (ICS)簡介 14
3.2 多頻道媒介存取控制協定 15
3.2.1 Dynamic Channel Assignment (DCA)簡介 15
3.2.2 Multi-radio Unification Protocol (MUP)簡介 16
3.2.3 Cluster-based Multi-channel Communications Protocols簡介 18
第四章 適應性頻道協調 25
4.1 Channel-Switch機制 25
4.2多頻道媒介存取控制協定 29
4.2.1 頻道配置 29
4.2.2 車輛狀態轉換機制 30
第五章 模擬分析 35
5.1模擬環境與參數設定 35
5.2 模擬結果 36
5.2.1 頻道使用率分析(實驗一) 36
5.2.2 傳輸效率分析─不保留CH封包(實驗二) 38
5.2.3 傳輸效率分析─保留CH封包(實驗三) 40
5.3 小結 41
第六章 結論與未來研究方向 42
參考文獻 43
作者簡歷 45
[1]IEEE 1609.1-2006, “IEEE Trial-Use Standard for Wireless Access in Vehicular Environments (WAVE)—Resource Manager,” 13 October 2006.
[2]IEEE 1609.2-2006, “IEEE Trial-Use Standard for Wireless Access in Vehicular Environments—Security Services for Applications and Management Messages,” 6 July 2006.
[3]IEEE 1609.3-2007, “IEEE Trial-Use Standard for Wireless Access in Vehicular Environments (WAVE)—Networking Services,” 20 April 2007.
[4]IEEE 1609.4-2006, “IEEE Trial-Use Standard for Wireless Access in Vehicular Environments (WAVE)—Multi-channel Operation,” 30 October 2006.
[5]IEEE P802.11p/D5.0, “Draft 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 7: Wireless Access in Vehicular Environments,” November 2008.
[6]Dedicated Short Range Communications (DSRC) Home, http://www.leearmstrong.com/DSRC/DSRCHomeset.htm.
[7]IEEE 802.11e-2005, “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 8: Medium Access Control (MAC) Quality of Service Enhancements,” 11 November 2005.
[8]A. Meier, “5.9GHz Dedicated Short Range Communication Design of the Vehicular Safety Communication Architecture,” 2005.
[9]曾煜棋, 潘孟鉉, 林致宇, 無線區域及個人網路-隨意及感測器網路之技術與應用, 知城圖書, 2006.
[10]S.-L. Wu, C.-Y. Lin, Y.-C. Tseng, and J.-P. Sheu, “A New Multi-Channel MAC Protocol with On-Demand Channel Assignment for Multi-Hop Mobile Ad Hoc Networks,” 2000.
[11]A. Adya, P. Bahl, J. Padhye, A. Wolman, and L. Zhou, “A Multi-Radio Unification Protocol for IEEE 802.11Wireless Networks,” in proc. of the First International Conference on Broadband Networks, 2004.
[12]X. Zhang, H. Su and H. H. Chen, “CLUSTER-BASED MULTI-CHANNEL COMMUNICATIONS PROTOCOLS IN VEHICLE AD HOC NETWORKS,” Wireless Communications, IEEE, Volume 13, Issue 5, pp.44-51, October 2006.
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