UMTS IMS 中 I-CSCF 之快取效能分析

Abstract

UMTS (Universal Mobile Telecommunications System) 的 IP 多媒體子系統 (IP Multimedia Subsystem; IMS) 提供多媒體的服務。在IMS 中，所有的來話都會先到達 I-CSCF (Interrogating Call Session Control Function)。I-CSCF 向 HSS (Home Subscriber Server) 詢問到用戶的 S-CSCF (Serving CSCF) 之後，由S-CSCF負責為用戶建立通話。本論文針對IMS通話建立的效能進行分析，並提出快取及容錯的機制以加速通話建立的程序。我們的研究指出，I-CSCF 上的快取機制能顯著地減少通話建立的延遲時間，容錯機制能有效地增加 I-CSCF 的可用性。

The IP Multimedia Core Network Subsystem (IMS) provides multimedia services for Universal Mobile Telecommunications System (UMTS). In IMS, any incoming call will first arrive at the Interrogating Call Session Control Function (I-CSCF). The I-CSCF queries the Home Subscriber Server to identify the serving CSCF (S-CSCF) of the called mobile user. The S-CSCF then sets up the call to the called mobile user. This thesis investigates the performance of the IMS incoming call setup. We also propose cache schemes with fault tolerance to speed up the incoming call setup process. Our study indicates that the I-CSCF cache can significantly reduce the incoming call setup delay, and checkpointing can effectively enhance the availability of I-CSCF.