UMTS Network Architecture

A UMTS system consists of three major subsystems:

• User Equipment (UE): it may be a mobile, a fixed station, a data terminal, etc. includes a USIM, which contains all of a user’s subscription information.
• Access Network: includes all of the radio equipment necessary for accessing the network.
• Core Network: Includes all of the switching nd routing capability for connecting to either the PSTN or a Packet Data Network , for mobility and subscriber location management and for authentication services.

UTRAN is Radio Access Network portion of WCDMA. It consists of one or more Radio Network Subsystems (RNS). Each RNS consist of only one Radio Network controller (RNC) and one or more Node Bs. The main purpose of UTRAN is to provide a connection between UE and the Core Network. The UTRAN offers Radio Access Bearer (RAB) to establish a call connection between the UE and core network. The characteristic of RAB differs depending upon the type service. RABs are characterized by Quality of service parameter like latency and Data Rate.
Different type of UTRAN Network interfaces are as follows:

• Iu interface – this is the interface that bridges the Core Network and the Radio Access Network.
• Iur Interface – this is the interface that carries the signaling and data link between different RNCs. Plays a great role in soft handover and transition.
• Iub Interface – The interface between the RNC and different Node Bs that carries signaling as well as data links.
• Uu Interface – The interface between different Node Bs and UE to carry the Signalling as well as data link over the air interface.