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UMTS was envisaged as a "universal" mobile telecommunications system with multiple access options and full IP packet support. However, 3GPP Rel99 is a single access technology, and its core is still switch centric. Rel4 further optimises the air interface. Rel5 first adds an IP multimedia core network sub-system (IMS) adjunct to the UMTS packet switched (PS) GPRS CN bearer. This adds basic PS call control trial capabilities. Rel6 will provide full UMTS packet call control (CC) capabilities (e.g.: security, emergency & QoS support). The Rel5/6 standards employ the text based call control protocol: SIP. Text based protocols are easier to develop than bit-wise presentations and likely to be more expediently taken to market. However, initial indications as to the delays associated with packet call control using SIP have concerned operators about the viability of IP-based services over a UMTS air interface. This has led UMTS vendors/operators to invest in the standardization of ways to wireless enable the efficient use of SIP with such measures as protocol compression. This paper explains GSM, UMTS circuit switched call control and SIP call control as applied to UMTS and then compares and contrasts the relative performance of both schemes using results derived from a UMTS system simulator called the Framework for Radio Architecture Modelling (FRAM).

With ever increasing penetration of IP technologies and the tremendous growth in wireless data traffic, the wireless industry is evolving the mobile core networks towards IP technology. The 3rd Generation Partnership Project (3GPP) is specifying an IP Multimedia Core Network Sub-System (IMS) in UMTS Release 5/6, which is adjunct to the UMTS GPRS CN. This IP-based network will allow mobile operators to provide commonly used Internet applications to wireless user. The UMTS IMS uses the Internet Engineering Task Force (IETF) defined text based Session Initiation Protocol (SIP), to control a wide range of anticipated IP-based services. Text based protocols are easier to develop than bit-wise presentations and likely to be more expediently taken to market, as they allow vendors/operators to open the session/application space to a much broader development community. This is likely to offer new services such as wireless multimedia calls, chat, presence and push services. This paper presents results of a performance evaluation of the SIP based Presence and Instant Messaging service as being standardised by 3GPP and IETF based on a model implemented in a UMTS system simulator called the Framework for Radio Architecture Modeling (FRAM).

3GPP Rel.5 specifies an IP multimedia core network sub-system (IMS) adjunct to the UMTS packet switched (PS) GPRS CN bearer and Rel.6 will let UMTS provide full packet call control (CC) capabilities (e.g. security, emergency and QoS support). The packet call control capabilities employ the IETF text based call control protocol SIP (session initiation protocol). Text based protocols have the advantage that they are generally easier to develop than bit-wise presentations. However, due to their larger message sizes, delays associated with packet call control using SIP have concerned operators about the viability of such services over a UMTS air interface. This has led development of message compression techniques for more efficient use of SIP. This paper provides a brief overview of GSM, UMTS circuit switched call control, and SIP based call control as applied to UMTS and then compares and contrasts the relative performance of the call control protocols using results derived from a UMTS system simulator called the Framework for Radio Architecture Modelling (FRAM).