In post "3G UMTS Network Architecture WCDMA Technology" discuss briefly about three major subsystems: User Equipment (UE) ,Access Network and Core Network. This session carries on to discuss general UTRAN Architecture.
The UTRAN architecture comprises of one or more Radio Network Controllers (RNCs), each controlling a number of base sites, known as Node B. Each grouping of RNC and its associated Node Bs are collectively known as a Radio Network Sub-system (RNS). Hence an UTRAN is comprised of one or more RNS.
Standard interfaces connect each RNS to the Core Network (both Circuit Switched
and Packet Switched Domains), and to the User Equipment. These interfaces are
known as IuCS, IuPS (This is the interface that bridges the Core Network and the Radio Access Network.), and Uu (The interface between different Node Bs and UE to carry the Signalling as well as data link over the air interface) respectively.
The UTRAN internal interfaces are also standardised. The Iur (This is the interface that carries the signaling and data link between different RNCs. Plays a great role in soft handover and transition) connects RNC (and
hence RNS), whilst the Iub (The interface between the RNC and different Node Bs that carries signaling as well as data links).
The term Node B refers to the base station equipment which communicates with the
subscriber’s handset via the radio link (and of course with the main network via a
telecoms link).
It provides radio resources for a UMTS network, and uses UMTS channel allocation to
communicate with the handset. It provides all the RF processing, enabling
transmission and reception information to and from the mobile terminal. This
information is encoded using the W-CDMA scheme.
A single UMTS channel can be used on adjacent Node B sites and in different sectors
of the same Node B antenna system. A typical Node B may support a three sector
antenna and one or two UMTS carriers, although it is possible to configure up to six
sectors and up to three UMTS carriers. Each sector can be used as a different cell.
Node B tasks are as follows:
RNC
The RNC controls the operation of multiple Node Bs, managing resources such
as allocating capacity for data calls, and providing critical signalling such as
connection set-up, plus switching and traffic routing functionality.
Compared to 2G systems, it is broadly equivalent to the BSC, but also includes some
functionality of the MSC. In particular, it enables autonomous Radio Resource
Management by the UTRAN by allowing RNCs to directly communicate (via the Iur
interface), eliminating this burden from the core network. So all handover processes,
even where moving between cells controlled by different RNCs, are kept within the
UTRAN. Compare this with the situation in GSM, where handover between different
BSC areas required involvement of the MSC, and hence the core network.
The RNC can manage many Node Bs, and allocates radio resources and maintains
the equilibrium of a live and dynamic network. It must also interface with the core
network to provide access to the network operator services, applications, Internet
and gateways to networks such as GSM and PSTN.
The Iub is the first example of a fully standardised base-station-to-controller interface
within commercial mobile networks, and is defined thus in order to increase
competition between manufacturers in this very costly part of the network. For
example it is now possible to source Node B and RNC equipment from different
vendors, and hence for specialist vendors for Node B only, for example, to enter the
market.
The key features of the RNC are:
The UTRAN architecture comprises of one or more Radio Network Controllers (RNCs), each controlling a number of base sites, known as Node B. Each grouping of RNC and its associated Node Bs are collectively known as a Radio Network Sub-system (RNS). Hence an UTRAN is comprised of one or more RNS.
Standard interfaces connect each RNS to the Core Network (both Circuit Switched
and Packet Switched Domains), and to the User Equipment. These interfaces are
known as IuCS, IuPS (This is the interface that bridges the Core Network and the Radio Access Network.), and Uu (The interface between different Node Bs and UE to carry the Signalling as well as data link over the air interface) respectively.
The UTRAN internal interfaces are also standardised. The Iur (This is the interface that carries the signaling and data link between different RNCs. Plays a great role in soft handover and transition) connects RNC (and
hence RNS), whilst the Iub (The interface between the RNC and different Node Bs that carries signaling as well as data links).
 |
| UTRAN Architecture and Terminology |
NodeB
subscriber’s handset via the radio link (and of course with the main network via a
telecoms link).
It provides radio resources for a UMTS network, and uses UMTS channel allocation to
communicate with the handset. It provides all the RF processing, enabling
transmission and reception information to and from the mobile terminal. This
information is encoded using the W-CDMA scheme.
A single UMTS channel can be used on adjacent Node B sites and in different sectors
of the same Node B antenna system. A typical Node B may support a three sector
antenna and one or two UMTS carriers, although it is possible to configure up to six
sectors and up to three UMTS carriers. Each sector can be used as a different cell.
Node B tasks are as follows:
- conversion of data to and from the radio interface
- forward error correction
- rate adaptation
- W-CDMA spreading & despreading
- QPSK modulation (Quadrature Phase Shift Keying)
- measuring the quality & strength of connection
- determining the frame error rate
- handover between different sectors on the same Node B (“softer handover”)
- participation in power control, enabling the user terminal to adjust its power (“inner
- loop power control”)
 |
| NodeB functions |
RNC
The RNC controls the operation of multiple Node Bs, managing resources such
as allocating capacity for data calls, and providing critical signalling such as
connection set-up, plus switching and traffic routing functionality.
Compared to 2G systems, it is broadly equivalent to the BSC, but also includes some
functionality of the MSC. In particular, it enables autonomous Radio Resource
Management by the UTRAN by allowing RNCs to directly communicate (via the Iur
interface), eliminating this burden from the core network. So all handover processes,
even where moving between cells controlled by different RNCs, are kept within the
UTRAN. Compare this with the situation in GSM, where handover between different
BSC areas required involvement of the MSC, and hence the core network.
The RNC can manage many Node Bs, and allocates radio resources and maintains
the equilibrium of a live and dynamic network. It must also interface with the core
network to provide access to the network operator services, applications, Internet
and gateways to networks such as GSM and PSTN.
The Iub is the first example of a fully standardised base-station-to-controller interface
within commercial mobile networks, and is defined thus in order to increase
competition between manufacturers in this very costly part of the network. For
example it is now possible to source Node B and RNC equipment from different
vendors, and hence for specialist vendors for Node B only, for example, to enter the
market.
The key features of the RNC are:
- management of radio resources
- channelisation code allocation
- QoS monitoring
- handover of users between cells on the same site (softer handover)
- handover of users between cells on different sites (soft handover)
- handover of users between different UMTS carriers (hard handover)
- handover of users to GSM networks (hard handover)
- power control management of user and Node B equipment
- network alarm correlation
- Controls functions of multiple Node Bs
- Radio resource management kept within the UTRAN
- Interfaces with core network
- Manages handover
- Power Control Management
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