基於ITU-T H.323建議標準之主動式「視訊電話服務」交換系統

Abstract

針對以H.323為建議標準之VoIP技術於目前現有環境下進行Telephony Service所遇之瓶頸限制，並考量Video Communication應用加入後之系統複雜度，而提出一”Video Telephony Service” Over Internet之解決方案。 目前學術界在H.323協定標準相關領域有不少理論、研究是關於服務品質控制（於網路端做QoS Control），但較少針對現今網路環境、架構限制、使用者習慣與系統整合等問題提出一既符合標準又兼具創新之系統架構，因此若能依此原則而進一步整合視訊電話應用以提供相關服務，應是頗值得研究與探討之主題，我們針對H.323所提出之建議架構，詳細檢視其交換流程（包含控制訊息與多媒體資料），並重新設計而提出一相容於其運作並可建構於各服務節點之”Video Telephony Service”應用導向交換系統，此即所謂「Active Switching」之概念，也實現所謂” Video Telephony Service” Over Internet之主流網路相容系統。 我們將對H.323 Protocol Stack其下各個協定之標準文獻與IEEE JSAV期刊於Vol. 15, No. 6, Aug. 1997刊載之一系列相關技術論文進行分析外，亦針對即時多媒體通訊系統之速率控制（Rate Control）、編碼設計（CODEC Design）、同步控制（Synchronization Control）、准入控制（Admission Control）等相關主題進行瞭解；另外對於目前網路實務環境（如：Ethernet、TCP/IP等）也需進行深入探討外，在實作上亦需對專用電話交換機介面（PBX Interface）、電腦電話整合規劃（CTI Planning）、集線/交換器設計（Hub/Switch Design）、視訊擷取卡應用（Video Capture Card Application）、視窗程式設計（Windows Programming）等各項技術進行整合、運用。

The study focuses on the solution of “Video Telephony Service” over Internet to solve the limitation of Telephony Service with VoIP technology based on H.323 standard under current environment, and considers the complex of system affiliated with Video Communication application. Presently, academic community had done lots of researches in H.323 protocol regarding QoS Control, Rate control, and Error control; however, it seldom concentrated on the current network environment, the structure limitation, user habit and system integration. Now it proposes a new structure based on H.323 and should review precisely the information exchange procedure including control message and multi-media data. It also redesigns a switching system for “Video Telephony Service” which is an application oriented switching system and could be constructed at every service node. This is just like the concept of “Active Switching”. It analyses each document of protocols under H.323 Protocol Stack and a serial of technique papers which is published in Vol.15, No. 6, Aug. 1997, IEEE JSAV journal and studies related topics of Rate Control, CODEC Design, Synchronization Control, and Admission Control. It also investigates and integrates current networking environment (Ex. Ethernet, TCP/IP), PBX Interface, CTI Planning, Hub/Switch Design, Video Capture Card Application, and Windows Programming.