UMTS: Universal Mobile Telecommunications System

Universal Mobile Telecommunications System (UMTS) is a key 3G mobile technology identified by the ITU. UMTS is the natural evolutionary choice for operators of GSM networks, a 2G mobile network. Using fresh radio spectrum to support increased numbers of customers in line with industry forecasts of demand for data services over the next decade and beyond, "UMTS" is synonymous with a choice of WCDMA radio access technology that has already been selected by approaching 120 licensees worldwide.

A UMTS network consist of three interacting domains; Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core network is to provide switching, routing and transit for user traffic. Core network also contains the databases and network management functions. The following is a list of key UMTS components:

• UMTS systems (including satellite)

• PublicLandMobile Network (PLMN)
• MSC/VLR or SGSN
• Location Area
• Routing Area (PS domain)
• UTRAN Registration Area (PS domain)
• Cell
• Sub cell

UMTS system uses the same core network as the GPRS and uses entirely new radio interface. The core network provides the switching, routing, transport, and database functions for user traffic. The core network contains circuit-switched elements such as the MSC, VLR, and gateway MSC (GMSC). It also contains the packet-switched elements SGSN and GGSN. The EIR, HLR, and AuC support both circuit- and packet-switched data. The Asynchronous Transfer Mode (ATM) is the data transmission method used within the UMTS core network.

The new radio network in UMTS is called UTRAN (UMTS Terrestrial Radio Access Network) and is connected to the core network (CN) of GPRS via Iu interface. The Iu is the UTRAN interface between the Radio network controller RNC and CN.