WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Wirel. Commun. Mob. Comput. 2012; 12:580–587 Published online 1 July 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/wcm.997 RESEARCH ARTICLE Enhanced video phone services for NGN/IMS Gong-Da Fan 1 , Chao-Chun Huang 1 , Yi-Bing Lin 2* , Chung-Shih Tang 1 , Chin-Ywu Twu 1 and Yun-Hui Wen 1 1 Chunghwa Telecom, Taiwan, Republic of China 2 Department of Computer Science, National Chiao Tung University, Hsinchu, Taiwan, Republic of China ABSTRACT A Next Generation Network (NGN) has been developed in Taiwan, where IP Multimedia Subsystem (IMS) plays an important role to offer IP-based multimedia services. Such NGN/IMS networks have also been deployed worldwide. However, details of commercial-grade NGN service implementations are seldom reported in public. In this paper, we show how existing video phone service can be enhanced through Chunghwa Telecom’s NGN/IMS. Specifically, we illustrate three examples including Multimedia on Demand (MOD) TV, Multimedia Ringback Tone (MRBT), and Easy Go (EzGo). We also measure the delay times for accessing these services. The measurements indicate that performance for these IMS-based services is satisfactory. Copyright © 2010 John Wiley & Sons, Ltd. KEYWORDS Next Generation Network; IP Multimedia Subsystem; mobile service * Correspondence Yi-Bing Lin, Department of Computer Science, National Chiao Tung University, Hsinchu, Taiwan, Republic of China. E-mail: liny@csie.nctu.edu.tw 1. INTRODUCTION In the Next Generation Network (NGN), IP Multimedia Subsystem (IMS) supports IP-based multimedia services through access networks including WCDMA, Wireless LAN, CDMA2000, broadband IP network, and fixed lines. Figure 1 illustrates a simplified NGN/IMS network archi- tecture [1,2]. In this figure, the NGN/IMS network (Figure 1(a) and (b)) connects to the Public Switched Telephone Network (PSTN) and Circuited Switched (CS) domain of the Public Land Mobile Network (PLMN; see Figure 1(e)) for fixed mobile convergence (FMC). IMS provides a stan- dard approach for access to the application network (Figure 1(d)) from User Equipment (UE) such as a fixed video phone (Figure 1(17)) in the broadband IP access network (such as xDSL and FTTx; see Figure 1(c)) or a mobile handset (Figure 1(4)) in the packet-switched (PS) domain of PLMN (Figure 1(f)). An example of PLMN-PS network is UMTS with the GPRS core network [1]. The Call Session Control Function (CSCF; Figure 1(2)) is responsible for call control. The Home Subscriber Server (HSS) or User Profile Server Function (UPSF; Figure 1(1)) is the master database containing subscription-related infor- mation for each IMS user. The Media Gateway Control Function (MGCF; Figure 1(5)) controls the connection of media channels in a Media Gateway (MGW; Figure 1(6)). The MGW connects toward the PSTN/PLMN-CS to pro- vide user media transport. The Session Border Controller (SBC; Figure 1(3)) supports the functions of topology hiding and NAT/firewall traversal. The Connectivity ses- sion Location and repository Function (CLF; Figure 1(7)) is a function element of Network Attachment Subsystem (NASS) defined by TISPAN NGN [2], which holds the IP address and the location information binding of an IMS user (usage of the CLF will be discussed in Section 5). Chunghwa Telecom has deployed the largest commer- cial NGN/IMS in Taiwan to provision enhanced voice, video, and Internet-based multimedia services. The current NGN/IMS capacity can accommodate about 500 000 sub- scribers in daily commercial operation. In this deployment, the CSCF is a Nokia Siemens Networks (NSN) CFX-5000, the MGCF is an NSN hiE9200, the MGW is an NSN hiG1100, the UPSF is an NSN CMS-8200, the SBC is an ACME SD 4000, the CLF is an Alcatel-Lucent SSC 5750. In Chunghwa Telecom’s NGN/IMS, video phone service is efficiently supported by the application network through the CSCF and the UPSF. The IMS application servers in this network will be elaborated in the subsequent sections. Based on Chunghwa Telecom’s video phone service, we have developed several enhanced services including Multi- media on Demand (MOD) TV, Multimedia Ringback Tone (MRBT), and Easy Go (EzGo). In this paper we show how 580 Copyright © 2010 John Wiley & Sons, Ltd.