Performance estimation of efficient UMTS packet voice call control

Abstract

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).