無線網路環境下網際網路電話之效能分析

Abstract

網際網路電話（VoIP）為目前IP網路上最具發展性的通訊方式之一。在無線行動環境下，頻寬資源有限，並且傳送之可靠性較有線環境為差。為了在無線行動網路中提供令人滿意的網際網路電話服務，必須保證網路的服務品質（QoS）。 隨著電波射頻技術的演進，頻寬大幅提升，各種無線網路下都可以提供網際網路電話服務。為達到電信等級的安全度，我們提出整合第三代行動網路與無線網路的認證方法，在無線網路環境下重複利用全球行動通訊系統（UMTS）的認證金鑰，並且針對IEEE 802.1X參數作效能分析以獲得較好的認證延遲效能。 此外，我們研究無線網路下網際網路電話封包的傳送效能。第三代行動合作通訊計畫（3GPP）標準文件允許被認證的無線網路透過無線接取閘道器/封包資料閘道器（WAG/PDG）接取第三代行動網路；然而，為確保電信等級的安全度，在行動終端設備（MS）和無線接取閘道器/封包資料閘道器間的網際網路電話封包必須以網際網路通訊協定安全性（IPsec）保護。我們分析在無線網路下以網際網路通訊協定安全性加密後的網際網路電話效能，檢視網際網路通訊協定安全性的額外負擔，包括：封包處理效能，封包遺失率，封包傳送延遲，以及傳送時間抖動。 最後，我們評估車用環境下網際網路電話的效能。基於M台灣計畫，我們在台北佈建全球互通微波存取（WiMAX）網路以支援高速行動寬頻服務，並在該網路環境中整合網際網路電話服務。我們研究在上述環境下網際網路電話的效能，其研究成果可作為未來其他先進的網路環境下分析網際網路效能時的參考。

Voice over Internet Protocol (VoIP) is a promising low-cost voice communication over IP networks. In a mobile/wireless environment, the radio resource is restricted and the reliability of the wireless transmission is much poor than that of the wired environment. To provide satisfactory VoIP services in the mobile/wireless network, the Quality of Service (QoS) of the network should be guaranteed. Due to the advances of various wireless technologies, the VoIP service is provisioned in different wireless networks. To achieve telecom grade security, we propose a WLAN-3G integrated security approach that reuses the UMTS authentication key in the WLAN environment and conduct a modeling study to tune the IEEE 802.1X parameters to yield better authentication delay performance. Furthermore, we investigate the VoIP packet delivery efficiency in the wireless environment (i.e., WLAN network). In 3GPP specifications, the authenticated WLAN MS is allowed to access the 3G network through the WAG/PDG. However, to ensure telecom grade security, the VoIP traffic between the MS and the WAG/PDG must be protected with IPsec. We analyze the performance of IPsec-based VoIP service in a IEEE 802.11b WLAN environment. The IPsec overheads in terms of throughput, packet loss rate, latency, and jitter are investigated. Finally, we present the VoIP performance in the vehicle environment. We conduct trials in the real WiMAX network which supports high-speed mobile broadband services and investigate the WiMAX-based VoIP of a Mobile Taiwan (M-Taiwan) funded program conducted during 2007-08 in the Taipei area. We investigate the VoIP performance in the wireless environment. These research results presented in this dissertation can be viewed as a useful foundation for further VoIP performance study in various advanced wireless environments.