由於手持移動裝置的發達，使用者常使用多媒體影音軟體播放影片，而隨著移動會有影片中斷或停頓的現象，這種現象是由於從舊的網路服務換手到新的網路服務造成的。IEEE 為了解決換手的問題，制定了802.21 來實現無縫換手，透過Media Independent Handover(MIH)支援不同的無線網路技術之間的換手，但仍然會有中斷的問題，這是因為換手時間過長，導致串流緩衝區耗盡。
本研究提出使用Received Signal Strength Indication(RSSI)動態調整串流緩衝區存量，減少換手時間帶來的影響，也利用RSSI 來決定換手時機的機制，以確保有足夠的串流網路頻寬，避免過晚的換手，進而達成無縫換手的方法。

As the handheld mobile devices developed, users often use multimedia software to play streaming video. While device moving, Streaming video will interrupt or pause,which is caused due to the handover from the old to the new network services network services. In order to solve the problem of handover, IEEE releases standard 802.21 Media Independent Handover (MIH). IEEE 802.21 supports seamless handover between different wireless networks. But Streaming video will still be interrupted, and this is because of handover time is too long, resulting stream buffer run out. This study proposes using Received Signal Strength Indication (RSSI) to dynamically adjusts the stream buffer size, reduce the impact of handover time, also using RSSI to determine timing of handover, make sure there is enough network bandwidth streaming, avoid too late handover, To achieve the goal of a seamless handover.

中文摘要	I 
英文摘要	II 
內文目錄	III 
圖表目錄	VI 

目   錄
第一章	緒論	1
1.1	前言	1
1.2	研究動機與目的	1
1.3	論文章節架構	2
第二章	背景知識與相關研究	3
2.1	換手的介紹	3
2.1.1	換手的分類	4
2.1.2	換手的網路相關技術	7
2.2	IEEE802.21 MIH	8
2.2.1	MIH Function Layer	8
2.2.2	MIH Services	10
2.2.3	MIH換手流程	15
2.3	串流緩衝區控制機制	15
2.3.1	串流緩衝區	15
2.3.2	漸進式調整畫面更新率機制	17
2.3.3	曲線式調整畫面更新率機制	18
2.4	RSSI的介紹	19
2.4.1	RSSI的 Rx Sensitivity 對照	20
2.4.2	WiFi 跟Rx Sensitivity的關係	23
第三章	控制機制的研究	25
3.1	系統問題的說明	25
3.2	解決方法及控制機制的研究	25
3.2.1	RSSI動態調整串流緩衝區控制機制	25
3.2.2	RSSI決定換手的時機的機制	27
3.3	案例說明	30
3.3.1	案例1	30
3.3.2	案例2	32
3.3.3	案例3	34
3.4	小結	35
第四章	模擬與研究分析	37
4.1	實驗環境	37
4.2	模擬實驗	38
4.2.1	實驗1	38
4.2.2	實驗2	40
4.2.3	實驗3	42
4.3	數據分析	43
第五章	結論與未來展望	46
參考文獻	 47

圖目錄

圖2.1 換手示意圖	3
圖2.2 水平換手	4
圖2.3 垂直換手	5
圖2.4 硬式換手	6
圖2.5 軟式換手	7
圖2.6 MIH Architecture [2]	9
圖2.7 SSL元件架構圖[2]	16
圖2.8 換手串流緩衝區的示意圖[3]	17
圖2.9 漸進式調整畫面更新率機制[3]	18
圖2.10 曲線式調整畫面更新率機制[4]	19
圖2.11 IEEE802.11a/g Data Rate	24
圖2.12 IEEE802.11b Date Rate	24
圖3.1 動態調整緩衝區示意圖	26
圖3.2 Bdynamic 線性圖	27
圖3.3 RSSI換手機制	29
圖3.4 案例1	30
圖3.5 案例1流程圖	31
圖3.6 案例2	32
圖3.7 案例2流程圖	33
圖3.8 案例3	34
圖3.9 案例3流程圖	35
圖4.1 實驗環境	37
圖4.2 實驗1	38
圖4.3 實驗1的距離跟速度的座標圖	39
圖4.4 實驗2	40
圖4.5 實驗2的距離跟速度的座標圖	41
圖4.6 實驗3	42
圖4.7 Playback without RSSI control	43
圖4.8 Playback with RSSI control	44

表目錄

表2.1 Link Events and MIH Events	10
表2.2 MIH and Link Commands	12
表2.3 Information Elements	14
表2.4 Symbol RSSI Lookup table	21
表2.5 Cisco RSSI Lookup table	22
表2.6 IEEE802.11a/g Data Rate	23
表2.7 IEEE802.11b Date Rate	23
表4.1 實驗1的距離跟傳輸速度的相對表	39
表4.2 實驗2的距離跟傳輸速度的相對表	41

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