UMTS Terrestrial Radio Access Network
The UMTS Terrestrial Radio Access Network, UTRAN short, is one of the hierarchical wireless access networks to a mobile network based on the UMTS standard. It is also called a Radio Network System (RNS). Other possible radio access networks are GERAN (GSM EDGE Radio Access Network, including: BSS) and E-UTRAN ( Evolved UTRAN).
A UTRAN consists of one or more RNA, each RNS consists of one base station (referred to in the context of UMTS, a NodeB), and that a radio network controller (RNC)
The RNA takes over the transfer of the data to and from the core network, manages radio resources, implemented the handoff in a cell change and acquires the encoding of the radio channels. It communicates with the core network (Core Network, CN ) via the Iu interface and to the terminals (user equipment, UE ) over the Uu interface. Various RNA communicate over the Iur interface to one another.
By WCDMA multiplexing the transmissions many mechanisms are realized, which were not provided by GSM and were also not needed. Thus, there are at UTRAN new restriction or access methods that were necessary only for the UMTS network.
An important characteristic of the UTRAN network is macro- diversity, in which the terminal (e.g., the mobile phone ) via two channels transmit exactly the same information, so that the RNC (the " ground station " ) an error- free signal from the two transmissions can be calculated. Here, often the terms are combining (English combined ) and splitting ( engl. share ) used to describe the processing of the two data streams. The macrodiversity among others a higher cell capacity of the UMTS network, and a better transmission power distribution can be ensured.