臺灣博碩士論文加值系統

Android 系統是基於Linux 核心的軟體平台和作業系統，其架構早期由 Google 規劃，之後再由各大手機製造商所組成的開放手機聯盟（Open Handset Alliance）開發，這個目前正熱門的行動作業系統跟以往各大手機廠所發展出的 Linux 系統最大的不同在於它開放原始碼，讓程式開發者可以輕易的利用 SDK ( Software Development Kit ) 開發各式各樣的應用。Android平台可以讓不同的行動通訊設備只要搭載此作業系統即可享受Android所提供的服務功能。
行動裝置在無線網路涵蓋範圍內自由移動過程中必會發生換手(Handoff)的情況，因為當行動裝置離開原先所連結的無線存取點(Access Point 簡稱AP)的涵蓋範圍就必需轉換到另一台AP上。本論文主要在探討Android手機切換無線基地台的議題。依照論文設定每七秒就對該地區作掃描的動作，掃描到的無線基地台扣掉訊號值低於-88 dbm的基地台，再從內定手機上的資料庫去比對篩選過後的各無線基地台的歷史平均連線時間和該無線基地台當下的訊號強度作分數上的運算，而後分配權重(當下強度:55%、歷史平均連線時間:45%)做出排名，並且定期更新排名表。搭配設定無線基地台訊號強度的換手門檻值(-88 dbm)來觸發換手流程，此門檻值是基於換手頻率和手機系統資源消耗的程度來設定。依此方法選出合適的無線基地台作為換手的對象。由此程序可以篩選出訊號良好且連線品質較佳的無線基地台。

Android is a Linux-based, core software platform and operating system. Its architecture was planned by Google in early times and then was developed by the Open Mobile Alliance (Open Handset Alliance) that consists of major handset manufacturers. The major difference between this alternative and popular mobile operating system is its open source. Programmers can easily use the SDK (Software Development Kit) to develop a wide range of applications. Mobile devices equipped with Android operating system can enjoy the services provided by Android.
Handover is a process that occurs when mobile devices move within wireless networks. When the mobile device leaves the coverage of an access point (AP), it needs to switch its connection over to another AP whenever available. This thesis addresses the handover of an Android handset among AP. We propose to scan for network availability every seven seconds and filter out any AP with received signal strength less than -88 dBm signal.
We then, calculate the weighted average scores from current signal strength (with weight 55%) and average connection time of the concerned AP in the past (with weight 45%.) Such score ranking is updated periodically, which is referenced when the handset decides to perform handover for detecting that its received signal strength from the current AP has fallen below the threshold -88 dBm. The threshold is chosen based on how frequently handover takes place and how much resource on the mobile phone system is consumed. Experiments show that our implementation, enables handover to an appropriate AP.

目 錄
摘 要 i
ABSTRACT ii
誌 謝 iv
目 錄 v
表 目 錄 vii
圖 目 錄 viii
第一章 緒論 1
1.1 研究動機與目的 1
1.2 論文架構 1
第二章 IEEE 802.21相關知識背景 2
2.1 IEEE 802.21 2
2.1.1 MIHF (Media Independent Handover Function) 3
2.1.2 MIES (Media Independent Event Service) 4
2.1.3 Media Independent Command Services (MICS) 6
2.1.4 Media Independent Information Service (MIIS) 8
2.1.5 服務接取點Service Access Points (SAPs) 10
2.2 IEEE 802.21相關文獻 11
第三章Android Background 12
3.1 Android 軟體架構 12
3.2 Android Activity生命週期 15
3.3 Android 應用元件 20
3.4 Android Wi-Fi Network Module 23
第四章 實作的方法與結果分析 26
4.1 實驗環境介紹 26
4.2 方法流程圖 29
4.3 Android Wi-Fi 有限狀態機 31
4.4 實作測試 33
4.5 實作結果 36
4.6 實作分析 38
第五章 結論與未來展望 39
5.1 結論 39
5.2 未來展望與論文可能遇到問題 39
參 考 文 獻 41

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