The document provides an overview of the UMTS Terrestrial Radio Access Network (UTRAN). UTRAN consists of radio network subsystems (RNS) which contain Node Bs and Radio Network Controllers (RNCs). The RNC is responsible for radio resource management and user data traffic handling. Node Bs handle radio transmission and reception within cells. The UTRAN uses various interfaces like Iu, Iur, and Iub which involve different protocol stacks in the control and user planes to enable communication between the UTRAN and core network and between network components.

1. OVERVIEW OF UMTS TERRESTRIAL RADIO
ACCESS NETWORK
(UTRAN)

2. OVERVIEW OF UMTS TERRESTRIAL RADIO ACCESS
NETWORK (UTRAN)
 UTRAN consists of a set of radio network subsystems (RNSs)
 The RNS has two main logical elements:
 Node B
 RNC (Radio Network Controller)
 RNS is responsible for the radio resources and transmission/reception in a set
of cells.

3. RNC (Radio Network Controller)
 An RNC is responsible for the use and allocation of all the radio resources of
the RNS to which it belongs.
 The RNC also handles the user voice and packet data traffic, performing the
actions on the user data streams that are necessary to access the radio
bearers.
 A Node B is responsible for radio transmission and reception in one or more
cells to/from the user equipment (UE).
Node B

4. A. UTRAN LOGICAL INTERFACES
APPLICATION PROTOCOL
1.Radio Access Network Application Part
(RANAP) in Iu,
2.Radio Network Subsystem Application
Part (RNSAP) in Iur
3.Node B Application Part (NBAP) in
Iub).

5. A. UTRAN LOGICAL INTERFACES
 The protocol structure contains two main layers,
 Radio network layer (RNL) – allows communication between UTRAN and
Core Network.
 Transport network layer (TNL) - allows communication between UE and
UTRAN.
 Each of the layers is again divided into two planes.
 Control Plane
 User Plane
 The control plane is used for all UMTS-specific control signaling.
 The application protocol is used for setting up bearers to the UE.
 The user plane includes data streams, and data bearers for data streams.

6. Iu Interface

7.  The control plane protocol stack consists of RANAP on the top of signaling
system 7 (SS7) protocols. The protocol layers are,
 Signaling Connection Control Part (SCCP)
 Message Transfer Part (MTP3-B)
 Signaling Asynchronous Transfer Mode (ATM) Adaptation Layer for
Network-to-Network Interface (SAAL-NNI).
 The SAAL-NNI is divided into 3 layers
1. Service-Specific Coordination Function (SSCF)
2. Service-Specific Connection-Oriented Protocol (SSCOP)
3. ATM Adaptation Layer 5 (AAL5)
 The IP-based signaling bearer consists of
 MTP3—User Adaptation layer (M3UA),
 Simple Control Transmission Protocol (SCTP)
 IP
 AAL5

8. Iur Interface:
The connection between two RNCs (serving RNC (SRNC) and drift RNC
(DRNC)) is the Iur interface.

9. Iub Interface:
The connection between the RNC and Node B is the Iub interface.
There is one Iub interface for each Node B.