在通訊傳輸與無線網路發展蓬勃的現代化社會，各家網路服務的業者(ISP)相繼著手於無線與通訊網路的整合應用，以期提供消費者更多元的網路服務，創造更高的核心價值。而在眾多的網路環境中，使用者該如何來選擇網路路徑來達到較佳的效能，則成為一項網路傳輸中相當重要的課題。
本篇論文為立基於異質無線網路中與802.21MIH共存的網路選擇演算法。本研究所討論的方法是以用戶端的應用程式為導向，針對不同的應用程式，設立不同的參數強度，以參數強度為依據選擇換手路徑，計算出最佳的使用效能，以求獲得更高的服務品質；如使用FTP下載軟體的人會對頻寬有較高的要求，而使用VoIP通話的使用者則會希望通話品質有較高的水準等等。
在本篇論文中共定義了三種主要的網路選擇方程式，並對三個方程式分別做出效能品質及電力消耗的模擬，並在模擬中加入衰弱臨界值(threshold)的判斷因素以求最佳的換手時間點，在換手次數與效能之中取得最佳平衡。在網路選擇的方程式中我們提出六個主要的參數以供判斷，在各種不同的網路中如WiFi，WiMAX等異質網路，以六個主要的參數判斷何者為最適合目前應用程式之網路。本論文提出之演算法是以結合IEEE 802.21 MIH為主，未來將結合動態調整的緩衝機制，以求在網路環境中達無縫之換手之成效。

Media Independent Handover (MIH) is a standard being developed by IEEE 802.21 to enable the handover of IP sessions from one layer access technology to another, to achieve mobility of end user devices. However, how to select an appropriate wireless network which can provide user a high performance service is still an open issue for the MIH.
We have discussed a network selection algorithm based on IEEE 802.21 MIH functions in this paper. The algorithm we proposed is used to select the most appropriate network for the applications user is using. For different applications, we made different weights to select different networks to achieve a higher performance or to maintain a higher network quality.
In this paper, we defined three main equations to select the most appropriate network. Also we have added threshold values to each application to reduce handover times. In the network selection equation, we have proposed six main parameters to decide which and when should the handover decision be made. The details of the comparison between the algorithm we proposed and the existing algorithm will be shown in the fourth part in this paper. In the future we will add a dynamic-adjusting buffer management mechanism to achieve seamless handover.

目錄
第一章	緒論	- 1 -
1.1  前言	- 1 -
1.2  動機與目的	- 2 -
1.3  論文架構	- 4 -
第二章	研究背景介紹	- 6 -
2.1	IEEE 802.21 MIH	- 6 -
2.1.1	MIH function 與Service Access Point (SAP)	- 6 -
2.1.2	MIH的三種服務	- 10 -
2.1.2.1	MIH Event Service	- 11 -
2.1.2.2	MIH Command Service	- 14 -
2.1.2.3	MIH Information Service	- 17 -
2.2	MIH的協定(Protocol)與訊框格式(Frame Format)	- 20 -
2.3	異質無線網路間的換手	- 21 -
2.4	網路選擇演算法	- 23 -
第三章	網路選擇演算法	- 25 -
3.1	網路選擇方程式之改進	- 25 -
3.2	參數的正規化	- 26 -
3.3	網路選擇方程式	- 28 -
3.3.1	FTP網路選擇方程式	- 28 -
3.3.2	VoIP網路選擇方程式	- 29 -
3.3.3	影音串流網路選擇方程式	- 30 -
3.4	網路選擇演算法	- 31 -
第四章  模擬結果	- 34 -
4.1	模擬環境介紹	- 34 -
4.2	模擬(一)：未加入臨界值之模擬	- 34 -
4.2.1	參數設置	- 35 -
4.2.1.1	權重的定義	- 36 -
4.2.1.2	模擬對照組	- 37 -
4.2.2	FTP應用程式模擬	- 37 -
4.2.2.1	網路吞吐量的比較	- 38 -
4.2.2.2	電力消耗之比較	- 39 -
4.2.2.3	FTP模擬中網路選擇的情形	- 41 -
4.2.3	VoIP應用程式之模擬	- 42 -
4.2.3.1	延遲的比較	- 42 -
4.2.3.2	電力消耗在VoIP應用程式中之比較	- 43 -
4.2.3.3	VoIP模擬中網路選擇的情形	- 44 -
4.2.4	影音串流模擬	- 46 -
4.2.4.1	抖動的比較	- 48 -
4.2.4.2	電力消耗在影音串流應用程式中之比較	- 49 -
4.2.4.3	影音串流模擬中網路選擇之情形	- 50 -
4.3	模擬(二)：加入臨界值之模擬	- 51 -
4.3.1	調整衰弱臨界值以改善換手次數頻繁	- 52 -
4.3.2	減少在FTP應用程式中之換手次數	- 52 -
4.3.3	減少在VoIP應用程式中之換手次數	- 55 -
4.3.4	減少影音串流應用程式中之換手次數	- 57 -
第五章  結論及未來展望	- 61 -
參考文獻	- 62 -







圖目錄
圖1.1無線網路的速度及覆蓋半徑的比較	- 3-
圖2.1 MIH Function基本架構圖	- 7-
圖2.2多重無線區域網路SAP結構圖	- 9-
圖2.3 MIH Event Service運作說明圖	- 12-
圖2.4 MIH Command Service運作流程說明圖	- 15-
圖2.5 MIH Information Service運作說明圖	- 18-
圖2.6 TLV格式圖	- 20-
圖2.7 MIH 訊框格式圖	- 21-
圖2.8無線區域網路系統之間的涵蓋結構圖	- 22-
圖3.1網路選擇演算法流程圖	- 31-
圖4.1模擬環境網路拓墣	- 35-
圖4.2 FTP吞吐量比較	- 39-
圖4.3 FTP耗電情形比較	- 40-
圖4.4 FTP模擬中AP選擇情形	- 41-
圖4.5 VoIP延遲比較	- 43-
圖4.6 VoIP電力耗損情形比較	- 44-
圖4.7 VoIP模擬中AP選擇情形	- 46-
圖4.8 JITTER說明圖(1)	- 47-
圖4.9 JITTER說明圖(2)	- 48-
圖4.10 影音串流JITTER比較圖	- 49-
圖4.11 影音串流電源消耗比較圖	- 50-
圖4.12 影音串流模擬中AP選擇情形	- 51-
圖4.13 FTP換手次數與臨界值之關係	- 53-
圖4.14 FTP總吞吐量與臨界值之關係	- 54-
圖4.15 VOIP換手次數與臨界值之關係	- 56-
圖4.16 VOIP平均誤碼率與臨界值之關係	- 57-
圖4.17判斷網路是否抖動劇烈的流程圖	- 58-
圖4.18影音串流臨界值與換手次數之關係	- 59-
圖4.19影音串流臨界值與平均抖動之關係	- 60-
 
表目錄
表2.1 MIH服務比較表	-10-
表2.2 MIH Event比較表	-13-
表2.3 MIH Event比較表	-15-
表3.1 各AP可用之資訊	-26-
表3.2 正規化後之各AP資訊	-28-
表4.1模擬環境參數設置	-36-

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