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系統識別號 U0002-2206201016163800
中文論文名稱 使用品質掃描機制提升車載行動網路中的換手效率
英文論文名稱 Improving Handoff Efficiency over VANET by QualityScan
校院名稱 淡江大學
系所名稱(中) 電機工程學系碩士班
系所名稱(英) Department of Electrical Engineering
學年度 98
學期 2
出版年 99
研究生中文姓名 詹弘麟
研究生英文姓名 Hung-Lin Chan
電子信箱 697450327@s97.tku.edu.tw
學號 697450327
學位類別 碩士
語文別 中文
口試日期 2010-06-11
論文頁數 59頁
口試委員 指導教授-吳庭育
委員-李維聰
委員-趙涵捷
委員-黃能富
委員-陳俊良
委員-吳庭育
中文關鍵字 行動車載網路  智慧型運輸系統  存取點控制器 
英文關鍵字 VANET  ITS  APC 
學科別分類 學科別應用科學電機及電子
中文摘要 車載行動網路是將無線通訊整合至車輛的新興智慧型運輸系統科技,智慧型運輸系統的應用包含著行車安全性、運輸效率、資訊及娛樂等應用。在車載的環境下主要的終端設備為汽車,與一般人攜行走動的終端設備來比較,其移動性較高,換手的行為將會經常發生,若換手造成的延遲過長時將會影響網路傳輸的品質,尤其對於一些即時性的網路服務將有重大的影響,故傳統的行動管理機制已經不能符合車載行動網路的需求,許多快速換手的機制相繼提出。然而一般選擇換手存取點的方式為選取最佳訊號強度的存取點當做換手的存取點,並沒有考慮到不同存取點的負載狀況,故不能使網路的頻寬有效的利用,當某些存取點過度忙碌時將會使服務的品質下降。
在車載的環境中,存取點可事先建置完成,並依照不同路段的車流量可以調整區域內存取點的數量以達到網路流量分散提高服務品質的目的,例如在容易塞車的路段相對地網路使用量較高,若是只有一個存取點做服務,勢必造成網路壅塞的狀況。我們提出一適用於車載環境的快速換手機制,除了減少換手的延遲並考慮到區域存取點的負載平衡,透過建置好的存取點控制器可以定期收集各存取點忙碌的狀況,並預測下一時刻的網路流量,經由計算過後的參數透過廣播訊標訊框時廣播給鄰近的行動車輛節點,行動車輛節點可依據此參數選取對本身服務品質最佳的存取點。如此一來,可以達到區域存取點的負載平衡並提高服務的品質,提升車載行動網路中的換手效率。
英文摘要 Vehicular ad hoc network (VANET) is an emerging intelligent transportation system (ITS) that integrates wireless communications with vehicles. ITS applications currently include driving safety, transportation efficiency, information and entertainment-related applications. Compared with handheld devices, the mobility of vehicles, the main terminals in VANETs, is obviously higher and the handoff procedure consequently occurs frequently. Too long handoff latency works upon the transmission quality, especially on some real-time network services. Since traditional mobility management mechanisms no longer meet the needs of VANETs, many fast handoff schemes were proposed. However, without considering the loading status of different APs, most handoff mechanisms choose the AP with the optimal signal strength as the handoff location. In such a manner, the network bandwidth cannot be utilized efficiently and the overload of some APs may degrade service quality.
In VANETs, APs can be established in advance. According to different traffic flow, the number of APs can be adjusted in order to distribute network traffic and improve service quality. For example, the network traffic is undoubtedly high in a crowded road section. If only one AP provides service, the network traffic is bound to be congested. Therefore, we proposed QualityScan, a fast handoff scheme for VANETs to reduce the handoff latency and keep the APs load-balanced by deploying AP controller (APC) that periodically collect the status of the APs in the subnet and predict the network traffic at the next moment. Based on the result parameter broadcasted in beacon frames, the neighboring MNs can determine the best AP for the service. Thus, the APs in the area can be load-balanced, the service quality can be improved, and the handoff efficiency over VANETs can be further enhanced.
論文目次 第一章 緒論 - 1 -
1.1 前言 - 1 -
1.2 動機與目的 - 1 -
1.3 論文章節架構 - 2 -
第二章 相關背景研究 - 4 -
2.1 車載行動網路(Vehicular Ad Hoc Network, VANET) - 4 -
2.1.1 交通資訊系統(Traffic Information System, TIS) - 5 -
2.2 基於IEEE 802.11無線網路下的換手 - 7 -
2.2.1 被動掃描 - 7 -
2.2.2 主動掃描 - 8 -
2.2.3 Layer2換手延遲 - 9 -
2.3 現有的快速換手機制 - 11 -
2.3.1 Neighbor Graphs方法介紹 - 12 -
2.3.2 SyncScan方法介紹 - 12 -
2.3.3 DeuceScan方法介紹 - 13 -
2.4 802.11無線網路的負載平衡 - 13 -
2.4.1 負載平衡指標(Load Balance Index) - 16 -
2.5 IEEE 802.11p - 17 -
2.6 IEEE 802.11e - 18 -
2.6.1 EDCA(Enhanced Distributed Channel Access) - 19 -
2.6.2 EDCA參數組合資訊元素(EDCA Parameter Set Element) - 21 -
第三章 品質掃描機制 - 23 -
3.1 車輛換手時間點的預測 - 25 -
3.2 依照接收到的掃描資訊選取最佳的換手AP - 27 -
3.3 區域存取點群組的流量預測 - 28 -
3.4 以服務取向暨流量預測的區域負載平衡 - 31 -
3.5 依照流量預測調整K值 - 33 -
3.6 換手條件 - 36 -
第四章 模擬環境及模擬結果分析 - 38 -
4.1 車行速度與換手延遲分析 - 38 -
4.2 負載分析 - 41 -
第五章 結論與未來展望 - 56 -
參考文獻 - 57 -
圖2.1 車載行動網路 - 5 -
圖2.2 國道高速公路交通資訊系統 - 6 -
圖2.3 訊標訊框格式 - 8 -
圖2.4 IEEE 802.11換手程序 - 10 -
圖2.5 IEEE 802.11e傳送佇列 - 19 -
圖2.6 EDCA 時序圖- 20 -
圖2.7 EDCA參數組合資訊元素 - 22 -
圖3.1 換手時間點示意圖- 25 -
圖3.2 系統架構圖- 27 -
圖3.3 區域存取點群組示意圖- 28 -
圖3.4 排隊理論參數示意圖- 29 -
圖3.5 選擇AP 示意圖 - 32 -
圖3.6 預測流量示意圖 - 34 -
圖4.1 車速與換手延遲關係圖 - 40 -
圖4.2 車速與換手延遲關係圖 - 41 -
圖4.3 模擬場景圖 - 42 -
圖4.4 車速與車輛密度關係圖 - 43 -
圖4.5 車道平均車量密度與車流量關係圖 - 44 -
圖4.6 平均車量密度與負載平衡關係圖(N=2) - 46 -
圖4.7 平均車量密度與負載平衡關係圖(N=3) - 46 -
圖4.8 平均車量密度與負載平衡關係圖(N=4) - 47 -
圖4.9 各AP的忙碌程度(N=2, D=1) - 48 -
圖4.10 各AP的忙碌程度(N=3, D=1) - 49 -
圖4.11 各AP的忙碌程度(N=4, D=1) - 49 -
圖4.12 各AP的忙碌程度(N=2, D=2) - 50 -
圖4.13 各AP的忙碌程度(N=3, D=2) - 50 -
圖4.14 各AP的忙碌程度(N=4, D=2) - 51 -
圖4.15 各AP的忙碌程度(N=2, D=3) - 51 -
圖4.16 各AP的忙碌程度(N=3, D=3) - 52 -
圖4.17 各AP的忙碌程度(N=4, D=3) - 52 -
圖4.18 各AP的忙碌程度(N=2, D=4) - 53 -
圖4.19 各AP的忙碌程度(N=3, D=4) - 53 -
圖4.20 各AP的忙碌程度(N=4, D=4) - 54 -
圖4.21 各AP的忙碌程度(N=2, D=5) - 54 -
圖4.22 各AP的忙碌程度(N=3, D=5) - 55 -
圖4.23 各AP的忙碌程度(N=4, D=5) - 55 -
表2.1 Layer2換手延遲統計表 - 11 -
表3.1 車輛速度對應換手時間點 - 26 -
表3.2 K值表 - 36 -
表4.1 模擬參數表 - 39 -
表4.2 模擬參數表 - 42 -
表4.3 車量密度與車流量關係表 - 44 -
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