utran arch

UTRAN Architecture

Public Land Mobile Network (PLMN)Public Land Mobile Network (PLMN)• A PLMN can be regarded as an

independent telecommunications entity.

• A Public Land Mobile Network is defined in the specifications as consisting of:

One or more switches with a common numbering plan and routing plan

Switches act as the interfaces to external networks

• The PLMN can be separated into Core Network Access Network

Core Network

Access Network

PLMN

System Architecture Overview

User Equipment

UMTS Terrestrial

Radio Access Network

Core Network

UU IU

UE UTRAN CN

UMTS High Level ArchitectureUMTS High Level Architecture

• To this definition, the 3GPP standards, added an additional architectural block, the User Equipment UE


Major Network Elements in UMTSMajor Network Elements in UMTS

PLMN, PSTN, ISDN

Internet, X25

Packet Network

UU

UE

CU

USIM

ME

Mobile Equipment

UMTS SIM

CN

MSC/VLR

SGSN GGSN

GMSC

HLR

Serving GSN Gateway GSN

Gateway MSC

Mobile Switching Centre

Home Location Register


IU

UTRAN

IUb

IUr

Node B

Node B

Node B

Node B

RNC

RNC

Radio Network Controller


Iu-ps

Iu-cs

IUb

Core Network (CN)Core Network (CN)

• The Core Network consists of: A Circuit Switched Domain A Packet Switched Domain

• Some CN entities may belong to both domains

CS Entities PS EntitiesCommon Entities


OSI speak

Entity - a common function, which performs a task.

Functions of the CNFunctions of the CN

• Switching

• Service Provision

• Transmission of user traffic between UTRAN and/or fixed network

• Mobility Management

• Operations, Administration and Maintenance


General Core Network ArchitectureGeneral Core Network Architecture

IU

CN

MSC/VLR

SGSN GGSN

GMSC

HLR

Serving GSN

Gateway GSN

Gateway MSC

Mobile Switching

Centre


Other SGSN

Other MSC

UTRAN

UTRAN

External Circuit

Switched Networks

External Packet Switched Networks

Iu-cs

Iu-ps

Gs

GnGn

Gr GcGi

Authentication Centre

AuC

Equipment Identity Register

EIR

CS Entities

Common Entities

PS Entities


Major Elements of the Core NetworkMajor Elements of the Core Network

• Home Location Register (HLR)

The database storing the master copy of a users profile

• Visitor Location Register (VLR)

The database holding a copy of a visiting users profile

• Mobile Switching Centre (MSC)

Switch for Circuit Switched Services

• Gateway MSC (GMSC)

• Serving GPRS Support Node (SGSN)

Router for Packet Switched Services

• Gateway GPRS Support Node (GGSN)


Shared Entities in the Core NetworkShared Entities in the Core Network

• All of the following entities are shared between the CS and PS domains:


Authentication Centre

Equipment Identity Register

SMS-Service Centre


Why Separate CS domains and PS domains?Why Separate CS domains and PS domains?

• Advantages of separation Simple evolution from

GSM/GPRS Low Risk Early Availability Service Continuity

• Disadvantages of separation Build and manage 2

networks Separate engineering and

dimensioning Greater Infrastructure Cost Duplicated Functions

Mobility Management in VLR and SGSN


Suggest some general advantages and disadvantages.

Circuit Switched DomainCircuit Switched Domain

• The CS domain deals with circuit switched type

connections and the associated signalling

Connections that require a dedicated resource

• Entities specific to the CS domain are:

MSC - mobile services switching centre

GMSC - gateway MSC

VLR - visitor location register


Packet Switched DomainPacket Switched Domain

• The PS domain deals with packet switched type

connections and associated signalling

Comprised of packets, each of which can be routed

independently over virtual routes.

• Entities specific to the PS domain are:

SGSN - Serving GPRS support node

GGSN - Gateway GPRS support node


UMTS System AreasUMTS System Areas

• Location Area

UEs registered on the CS domain report their

position in terms of a Location Area

UEs in idle mode monitor Location Area Identities

(LAIs) and report changes

Stored in the visitor location register, VLR



• Routing Area RA

UE’s registered on the PS domain report their position

in terms of a Routing Area

UE’s in both idle and connected mode monitor Routing

Area Identities (RAIs) and support changes

Stored in the Gateway GPRS support node, SGSN



• UTRAN Registration Area

Used when a signalling/traffic connection is

established

A subset of the Routing Area

Only relevant to PS mode of operation

Used by the radio network controller RNC


General UTRAN ArchitectureGeneral UTRAN Architecture

UU IU

UE

UTRAN

IUb

IUr

Node B

Node B

Node B

Node B

RNC

RNC



Iu-ps

Iu-cs

IUb

CN (MSC)

CN (SGSN)


Elements of UTRANElements of UTRAN

• Radio Network Controller Owns and controls radio resources in its domain (BSC in GSM)

Service Access Point for all services that UTRAN provides for the CN

Note: Service RNC (SRNC) and Drift RNC (DRNC) are subsets

• Node B Acts as the radio base station (BTS in GSM)

Converts the data flow between the Iub and Uu interfaces


OSI speak

SAP - link between two entities.

Service - exchange of parameters

Functions of UTRANFunctions of UTRAN

• Provision of Radio Management & Control

• System access control

• Security and privacy

• Handover (Hard and Soft)


Provision of Radio Management & ControlProvision of Radio Management & Control

• Radio bearer set up and release (RNC and UE)

• Allocation and release of physical radio channels (UTRAN)

• Allocation of downlink channelisation codes (Controlling RNC ie: CRNC)

• Packet data transfer over radio function (UTRAN and UE)

• Radio channel coding and control (UTRAN and UE)

• Initial access detection and call handling (UTRAN)

• Power control Uplink Outer Loop (SRNC and Node B) All other control (UTRA and UE)

System Access ControlSystem Access Control

• Admission control (CRNC)

• Congestion control (UTRAN) RNC knows whether Node B has sufficient power

and spare codes

• System information broadcasting (UTRAN)

Security and PrivacySecurity and Privacy

• Use of temporary identifier

• RNTI- Radio Network Temporary ID (UTRAN)

• Encryption

HandoverHandover

• Radio environment survey (UTRAN-UE)

• Handover decision (RNC-UE)

• Macrodiversity control (SRNS-DRNS)

• Handover control (UTRAN)

• Handover (UTRAN or CN)

• SRNS relocation (RNC and CN)

• Inter-system handover (UTRAN, CN and UE)

General UE ArchitectureGeneral UE Architecture

UU

UE

CU

USIM

ME

Mobile Equipment

UMTS SIM

UTRANTerminal

Equipment


Functions of the UEFunctions of the UE

• Display and User interface

• Holds the authentication algorithms and keys

• User end termination of the air interface

• Application platform


Elements of the UEElements of the UE

• Mobile Equipment The radio terminal used for radio communication over

the Uu interface

• UMTS Subscriber Identity Module The smartcard that holds the subscriber identity,

authentication and encryption keys etc

• Additionally the Terminal Equipment This carries the application specific user interface


Major Interfaces in UMTSMajor Interfaces in UMTS

• There are four major new interfaces defined in UMTS

Iu

The interface between UTRAN and the CN

Iur

The Interface between different RNCs

Iub

The interface between the Node B and the RNC

Uu

The air interface

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


IIu u - the Core Network to UTRAN Interface- the Core Network to UTRAN Interface

• There are two parts to the Iu interface

Iu-ps connecting UTRAN to the PS Domain of the CN

Iu-cs connecting UTRAN to the CS Domain of the CN

• No radio resource signalling, travels over this interface

The Iu interface divides the UMTS network into the radio specific UTRAN and the CN.

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


IIurur - the Inter-RNC Interface - the Inter-RNC Interface

• The Iur interface allows soft handovers between Node-Bs attached to different RNCs

• It is an open interface to allow the use of RNCs from different manufacturers

• Its functions may be summarised: Support of basic inter-RNC

mobility Support of Dedicated and

Common Channel Traffic Support of Global Resource

Management

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


IIubub - the RNC to Node-B Interface - the RNC to Node-B Interface

• The Iub is an open interface to allow the support of different manufacturers supplying RNCs and Node-Bs

• Its major functions are: Carries dedicated and common

channel traffic between the RNC and the Node-B

Supports the control of the Node-B by the RNC

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


UUuu - the Air Interface - the Air Interface

• Clearly the Uu must be standardised to allow multiple UE vendors to be supported by a network

• The major functions of the Uu are to:

Carry dedicated and common channel traffic across the air interface

Provide signaling and control traffic to the mobile from the RNC and the Node-B

RNC

Node-B

RNC

UE

CN

Uu

Iu

Iub

Iur


UMTS Interface ImplementationUMTS Interface Implementation

ATM/IP Network

RNCNode B

Node B

Node B

MSC

RNC

SGSN

Node B

Iub

Iu_cs

Iu_ps

Iur


Additional Access NetworksAdditional Access Networks

• The UMTS CN is being designed with the possibility of interfacing to additional Access Networks other than UTRAN

GRAN - GSM/GPRS Radio Access Network

ERAN - EDGE Radio Access Network

HiperLAN2 - Broadband Radio Access Network (BRAN)

DECT - Digital Enhanced Cordless Telephony

UMTS-CN

DECT

HiperLAN2 GRAN

ERAN

UTRAN


Architecture of a UMTS bearer serviceArchitecture of a UMTS bearer service

TE TEUE UTRAN CNedge node

CNgateway

End-to-End

TE/UE Local Bearer UMTS Bearer External Bearer

Radio Access Bearer CN Bearer

Radio Bearer Iu Bearer Backbone Network

UTRA FDD/TDD Physical Bearer


Each bearer service on a specific layer provides services using layers below.

UMTS Protocol StratumsUMTS Protocol Stratums

• In order to provide separation between radio access functionality and service quality provision, protocols in UMTS are divided into two stratums

• Access Stratum Encompasses layers 1 and 2 of

the OSI 7 layer model, and the lower part of layer 3

• Non-access Stratum Encompasses layers 4 to 7 of

the OSI 7 layer model, and the upper part of layer 3

Non A

ccess Stratum

Access S

tratumL1 L1 L1L1

L2L2L2L2

L5L5

L4L4

L6 L6

L7 L7

L3 lower L3 lower L3 lower L3 lower

L3 upper L3 upper

Uu IuUE UTRAN CN


UMTS QoS ClassesUMTS QoS Classes• Conversational

Speech over CS bearer Voice over IP, PS bearer Delay critical, imposed by human perception

• Streaming Multimedia streaming Using buffers, for non-real time delivery; real-video, real-audio

• Interactive Web browsing, database retrieval Round trip delay time is a key parameter

• Background E-mail Delay:- 10s of seconds or even minutes


UTRAN

UTRAN

UTRANUTRAN

• UTRAN is the UMTS Terrestrial Radio Access Network UTRAN Radio Network SubSystem UTRAN internal interfaces

Iub link between Node B and RNC Iur link between RNC and RNC Iu link between RNC and CN

UTRAN Protocol Layers Non-Access Stratum Access Stratum

UTRAN

Radio Network Subsystem (RNS)Radio Network Subsystem (RNS)

• A Radio Network Subsystem consists of:

A single RNC One or more Node B’s Cells belonging to Node B’s

• The UMTS equivalent of the GSM BSS

RNC

Node B

Cell

Cell

Cell

Node B

Cell

Cell

Cell

Iur

Iu

Uu

UTRAN

Radio Network Controller (RNC)Radio Network Controller (RNC)

• Responsible for the use and integrity of the radio resources within the RNS

• Responsible for the handover decisions that require signalling to the UE

• Provides a combining/splitting function to support macrodiversity between different Node Bs

UTRAN

RNC

Node B

Cell

Cell

Cell

Node B

Cell

Cell

Cell

Iur

Iu

Uu

Node BNode B

• Logical node responsible for radio transmission / reception in one or more cells to / from the UE

• Dual mode Node B can support FDD and TDD mode

• Interface between the radio layer and transport layer

UTRAN

RNC

Node B

Cell

Cell

Cell

Node B

Cell

Cell

Cell

Iur

Iu

Uu

CellCell

• A cell/sector is an area of radio coverage.

RNC

Node B

Cell

Cell

Cell

Node B

Cell

Cell

Cell

Iur

Iu

Uu

UTRAN

Handover in UMTSHandover in UMTS

• There are three basic types of handover Intra frequency handovers

Handovers between 2 UMTS carriers at the same frequency These can be soft handovers

Inter frequency handovers Handovers between 2 UMTS carriers at different frequencies These are hard handovers

Inter system handovers Handovers between UMTS and GSM carriers These are hard handovers

UTRAN

Handover Sets in UMTSHandover Sets in UMTS

• Active Set Cells forming a soft handover connection to the mobile

• Candidate Set Cells not presently used in soft handover but who qualify

for soft handover based on Pilot, Ec/Io levels.

• Neighbour Set Those cells which are continuously monitored by the

mobile. The Pilot, Ec/Io levels are not strong enough to be added to the Active Set.

UTRAN

= 2Cell A and Cell C

= 2Cell A and Cell B

Handover Decisions in UMTSHandover Decisions in UMTS

Pilot Ec/Io

Direction of Travel

Window_DROP

Drop Time Delay

Window_ADD

Add Time Delay Replace Time Delay

Window_REPLACE

Active set = 1Cell A

UTRAN

A Active

B Active

C Active

Macrodiversity between Node B’sMacrodiversity between Node B’s

• If an active set consists of two connections to cells parented to different Node Bs then the combining of the two channels occurs at the RNC

• This is known as a soft handover

• This doubles the transmission ‘cost’ of the call

RNC

Node B

Cell

Cell

Cell

Node B

Cell

Cell

Cell

Iur

Iu

Uu

UTRAN

Macrodiversity between Cells on the Macrodiversity between Cells on the Same Node BSame Node B

RNC

Node B

Cell

Cell

Cell

Node B

Cell

Cell

Cell

Iur

Iu

Uu

• If an active set consists of two connections to cells parented to the same Node B then the combining of the two channels occurs at the Node B

• This is known as a softer handover

• This has no transmission implication (but does have capacity implications) if cells are collocated.

UTRAN

Protocol Model for UTRAN InterfacesProtocol Model for UTRAN Interfaces

• Protocol structures in UTRAN are designed in layers

and planes.

• They are seen as logically independent of each

other

However they will physically interact.

• Being logically independent allows for changes to

blocks in the future,

UTRAN

theoretically!

General Protocol Model for General Protocol Model for UTRAN Terrestrial InterfacesUTRAN Terrestrial Interfaces

UTRAN

Horizontal Layers in the General Protocol ModelHorizontal Layers in the General Protocol Model

• All UTRAN related issues are only visible in the

Radio Network Layer

• The Transport Layer simply represents standard

transport technology for use in UTRAN

e.g. ATM and appropriate ATM Adaptation Layers AAL2 ( voice ) and AAL5 ( data )

UTRAN

Vertical Planes in the General Protocol ModelVertical Planes in the General Protocol Model

• The Control Plane is provided for all UMTS specific

control signalling including:

Application Protocols

Signalling Bearers

• The User Plane is provided for all data sent and

received by the user including:

Data Streams

Data Bearers

UTRAN

Vertical Planes in the General Protocol ModelVertical Planes in the General Protocol Model

• The Transport Network Control Plane also includes the Access

Link Control Application Part, ALCAP.

UTRAN

Transport Network

User Plane

Transport Network

User Plane

Transport Network Control Plane

ALCAP

ALCAP - Access Link Control Application PartALCAP - Access Link Control Application Part

• ALCAP sets up the transport bearers for the User Plane

• The independence of the User and Control Plane

assumes that an ALCAP signalling transaction takes

place.

UTRAN

Iu, the UTRAN-CN InterfaceIu, the UTRAN-CN Interface

• The Iu has two different instances.

Iu-CS for circuit switched connections

Iu_PS for packet switched connections

• Originally proposed as one interface but the

differences between circuit and packet switched

services has produced two.

• The Control plane is the same as far as possible!

UTRAN

• The Iu-CS control plane

RANAP - radio access network application part

Broad-band SS7 ( Network-Network Interface NNI )

ATM - AAL 5

• The Iu-CS transport network control plane

Signaling protocol for setting up ATM AAL2

Broad-band SS7

ATM - AAL 5

• The Iu-CS user plane.

ATM - AAL2 reserved for each CS connection

Protocol structure for the Iu-CSProtocol structure for the Iu-CS

UTRAN

Protocol structure for the Iu-CSProtocol structure for the Iu-CS

UTRAN

Protocol structure for the Iu-PSProtocol structure for the Iu-PS• The Iu-PS control plane

RANAP - radio access network application part Broad-band SS7 ( NNI ) or IP based signalling bearers ATM - AAL 5

• The Iu-PS transport network control plane NONE required

the GPRS tunneling protocol only requires the IP addresses which

RANAP has supplied.

• The Iu-PS user plane.

ATM - AAL5 ( multiple packet data flows are multiplexed onto several

permanent virtual connections PVCs ) Each flow uses GTP-U, UDP

connectionless transport and IP addressing.

UTRAN

Protocol structure for the Iu-PSProtocol structure for the Iu-PS

UTRAN

RANAPRANAP• The functionality of the RANAP is performed through

Elementary Procedures EP’s

• RANAP has 12 defined functions

UTRAN

Relocation Iu Release Radio Access BearerManagement

Paging Location reporting Common IDManagement

Security Mode Control UE-CN signallingtransfer

OverloadManagement

Reset ReportingUnsuccessfultransmitted data

Management ofTracing

Iur, the RNC-RNC InterfaceIur, the RNC-RNC Interface

• The Iur provides support for four distinct functions:

Inter RNC Mobility

Dedicated Channel Traffic

Common Channel Traffic

Global Resource Management

• The Radio Network System Application Part, RNSAP is

therefore divided into four modules.

UTRAN

RNSAP Iur1: Inter RNC MobilityRNSAP Iur1: Inter RNC Mobility

• Iur1 provides for the mobility of the user between two RNCs but

does not support the exchange of user data traffic.

• If the network fails to provide this then the only means of mobility

is to disconnect from RNS1 and reapply for connection in RNS2

UTRAN

Cell

Cell

RNSAP Iur2: Dedicated Channel TrafficRNSAP Iur2: Dedicated Channel Traffic

• Iur2 sets up and maintains a dedicated channel between two RNCs

• Used in inter-RNC soft handover.

• Provides the serving SRNC with the capability to manage the radio

links in drift DRNCs

UTRAN

Cell

CellSRNC

DRNC

RNSAP Iur3: Common Channel TrafficRNSAP Iur3: Common Channel Traffic

• If Iur3 is not implemented then every time an inter-RNC cell

update takes place then that RNC becomes the serving RNC.

UTRAN

Cell

CellSRNC

RNC

RNC

SRNC

SRNC

RNC

No Iur3

RNSAP Iur4: Global Resource ManagementRNSAP Iur4: Global Resource Management

• This function is considered optionally as it does not transmit

any user data across the Iur.

• However it does provide useful information

transfer of cell measurement between RNCs

transfer of Node B timing information between RNCs

UTRAN

Protocol Structure for IurProtocol Structure for Iur

UTRAN

Iub RNC-Node B InterfaceIub RNC-Node B Interface

• Iub user plane, defines every type of transport channel, using

AAL2

• Iub signalling control plane, is divided into 2 essential

components; NBAP-C Common Node B application part NBAP-D dedicated Node B application part

UTRAN

NBAP-C

Set-up of 1st radio link to the UE

Cell configuration

Handling of RACH/FACH and PCH

NBAP-D

Addition, release of radio links

Handling of softer handover

Handling of dedicated and shared channels on a Node B - UE.x basis

Protocol structure for the IubProtocol structure for the Iub

UTRAN

Note:

SSCF service specific co-ordination function AAL set-up

UNI .. user - network interface

SSCOP service specific connection oriented protocol AAL set-up

utran arch

Documents

ps domains

domainthe cs domain

domainthe ps domain

core networkall

following entities

domaina packet

type connections

msc mobile services