臺灣博碩士論文加值系統

儘管目前在H.323系列標準方面的研究繁多，但大部分學術界研究僅針對理論的觀點出發，很少考慮到實作的可行性，本篇論文的目的即在考量當今網際網路限制以及媒體資料的即時性，以實作的角度進行研究，提出一套H.323多媒體通訊系統的完整設計。
論文中提出一種內建式IP交換機設計方法與裝置架構。首先，在傳統電路式交換機直接內建VOIP功能；藉由此方法，取代外加VOIP方式以增進QoS。我們的VOIP採用嵌入式系統（Embedded System）架構，通信協定採用ITU所訂定H.323多媒體通信標準，並且對交換機與IP控制方式進行設計。
另外利用網路性能檢測機制提高IP電話服務品質，使用一個能夠接收和分析RTCP封包的監控程序，並結合其他網路管理程序，可以根據網路的即時運行情況，主動調整語音壓縮機制，改變資料傳輸量以提升QoS；並由模擬結果證實此方法確實可行。

In this thesis, we have developed a communication system base on H.323 multimedia communication protocol for transmitting multimedia data on the band-limited Internet. Instead of building an additional VOIP module outside of the traditional circuit switch, we directly implemented it into an embedded switching system for the sake of improving the QoS.Additionally, we also proposed a networking performance diagnostic mechanism, which is a combination of the procedure that can receive and analyse RTCP packet and other network management procedures,to improve the service quality. Furthermore, according to the real-time network situation, the mechanism can also automatically adjust voice compression rate to increase the QoS. Finally, the simulation results show that our system is effective.

表目錄III
圖目錄IV
第一章緒論1
1.1 背景1
1.2 範疇4
1.3 論文組織5
第二章相關研究6
2.1 VOIP現況6
2.2 VOIP信號方式9
2.3 IP電話標準11
2.4 VOIP 對QOS的要求14
第三章系統設計與實現21
3.1 系統結構21
3.2 RAS模組25
3.2.1 網守搜尋(Gatekeeper Discovery)25
3.2.2 端點註冊(Endpoint Registration)26
3.2.3 端點定位(Endpoint Location)27
3.2.4 接入許可與退出(Admissions and Disengage)27
3.2.5 頻寬調整(Bandwidth Change)28
3.2.6 狀態與資源(Status and Resource)29
3.3 呼叫信令模組30
3.3.1 無Gatekeeper的基本呼叫建立過程30
3.3.2 兩端點註冊同一個Gatekeeper30
3.3.3 出局啟動程序(Outgoing Setup Procedure)31
3.3.4 入局啟動程序(Incoming Setup Procedure)32
第四章服務品質控制33
4.1 IP傳輸對QOS 支持33
4.2 排隊規律(QUEUING DISCIPLINE)35
4.3 語音播放機制38
4.4 自我調整能力（ADAPTIVE）機制40
4.5 驗證模型(VALIDATION MODEL)43
第五章結論51
5.1 研究成果51
5.2 未來工作52
參考文獻53
附錄A RAS消息一覽表55
附錄B RAS模組流程圖56
附錄C 呼叫信令消息一覽表70
附錄D 呼叫信令模組流程圖71

[1] ITU-T Recommendation H.323, “Infrastructure of audiovisual services — Systems and terminal equipment for audiovisual services,” 1999.
[2] ITU-T Recommendation H.225, “Call signalling protocols and media stream packetization for packet-based multimedia communication systems,” 1997.
[3] ITU-T Recommendation H.245, “Control protocol for multimedia communication,” 2000.
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[22] ITU-T Recommendation Z.100 , “CCITT Specification and description language (SDL),” March 1993.
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