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25 series - Radio interface access stratum and the radio access network

25.319 - Not available in this release Up to the 3GPP specifications 25.401 - UTRAN overall description 25.993 - Typical examples of Radio Access Bearers (RABs) and Radio Bearers (RBs) supported by Universal Terrestrial Radio Access (UTRA) 25.931 - UTRAN functions, examples on signalling procedures 25.922 - Radio resource management strategies 25.442 - UTRAN implementation-specific O&M transport 25.402 - Synchronization in UTRAN Stage 2 25.346 - Introduction of the Multimedia Broadcast/Multicast Service (MBMS) in the Radio Access Network (RAN); Stage 2 25.305 - User Equipment (UE) positioning in Universal Terrestrial Radio Access Network (UTRAN); Stage 2 25.309 - FDD enhanced uplink; Overall description; Stage 2 25.308 - High Speed Downlink Packet Access (HSDPA); Overall description; Stage 2 Uu interface Iub interface Iupc interface Iur interface Iu interface Node B Node B Node B Node B


This diagram shows the three main components of UMTS. The core network handles functions that are independent of the chosen radio access technology (such as routing and billing), while the radio access network handles radio communications to and from the mobile, which is known as the UE. It also shows some of the components within the radio access network. The Node B transmits and receives signals to and from the UE, while the radio network controller manages a group of Node B's. Also shown is an optional component known as the SAS, which is used in UE location measurement.

The 25 series protocols define functions and messages that directly involve the radio access network. These include the internal operation of the radio access network, and the interfaces from the radio access network to the mobile and the core network. They are distinct from the non-access stratum protocols in the 24 series, which define messages between the UE and the core network that pass transparently through the UTRAN. Note that the 25 series includes communications between the radio access network and the core network; the 28 series is hardly used at all.


FDDFrequency division duplex
HSDPAHigh speed downlink packet access
HSUPAHigh speed uplink packet access
MBMSMultimedia broadcast and multicast service
O&MOperation and maintenance
RNCRadio network controller
SASStandalone SMLC
SMLCServing mobile location centre
TDDTime division duplex
UEUser equipment
UMTSUniversal mobile telecommunication system
UTRANUMTS terrestrial radio access network
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