Introduction

The cellular networks have evolved considerably over the period. The early cellular networks suffered from many limitations and carried only speech. Today's the cellular systems like GPRS, carry packet switched data and support various type of application like Internet browsing, email access etc. In modern days the emphasis is on integration of all kinds of services like web access, file transfer and facsimile with the traditional voice services. The cellular networks are now heading towards all IP based network and it is likely that in future all services will be made available over IP. The 3G (Third Generation) cellular system is a step towards standardization of the next generation mobile cellular networks.

The third generation systems will support high speed packet switched data (up to 2Mbps) and will be next step beyond the GPRS. In fact GPRS is considered to be a transition step from second generation cellular systems to third generation cellular systems. The 3G systems are expected to be accepted world-wide and the subscriber would be able to get the mobile services from anywhere in the world without replacing his handset or SIM card. The subscriber would also get same environment and services in the visiting network as in his home network also being independent of the terminal. Apart from this, the modern generation cellular systems will provide with the framework to build various kind of services (like VPN and conferencing) on the top of core cellular networks.

Currently the 3G cellular systems are being evolved from the existing cellular networks. Despite the efforts of standardization, UMTS (Universal Mobile Telecommunication System) and CDMA-2000 are the two main networks which are likely to exist. Both these systems use CDMA technology. The UMTS system is being promoted by ETSI (European Telecommunication Standards Institute) and is a successor of GSM. CDMA-2000 is successor of IS-95 and is expected to be used in North America. In this report we will consider the features and architecture of UMTS system.