Introduction to UMTS USR7 FOR TRAINING PURPOSES ONLY

Introduction to UMTS USR7 FOR TRAINING PURPOSES ONLY A basic architectural split is between the user equipment (terminals) and the infrastructure. This results in two domains: the User Equipment Domain and the Infrastructure domain. User equipment is theequipment used by the user to access UMTS services. User equipment has a radio interface to theinfrastructure.

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Objectives Version 1 Rev 0

Objectives

On completion of this chapter the student should be able to:

• Name and state the purpose of the UMTS Domains

• Describe the architecture of a UMTS network

• Describe the purpose of the major network components

• Describe the options for evolution to future releases

FOR TRAINING PURPOSES ONLY - THIS MANUAL WILL NOT BE UPDATED 2-3

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Domain split

A basic architectural split is between the user equipment (terminals) and the infrastructure This results

in two domains: the User Equipment Domain and the Infrastructure domain User equipment is the

equipment used by the user to access UMTS services User equipment has a radio interface to theinfrastructure The infrastructure consists of the physical nodes which perform the various functionsrequired to terminate the radio interface and to support the telecommunication services requirements

of the users The infrastructure is a shared resource that provides services to all authorised end userswithin its coverage area The reference point between the user equipment domain and the infrastructuredomain is termed the "Uu" reference point (UMTS radio interface)

User equipment Domain

This domain encompasses a variety of equipment types with different levels of functionality Theseequipment types are referred to as user equipment (terminals), and they may also be compatible withone or more existing access (fixed or radio) interfaces e.g dual mode UMTS-GSM user equipment.The user equipment may include a removable smart card that may be used in different user equipment

types The user equipment is further sub-divided in to the Mobile Equipment Domain (ME) and the

User Services Identity Module Domain(USIM) The reference point between the ME and the USIM istermed the "Cu" reference point

Mobile equipment Domain

The Mobile Equipment performs radio transmission and contains applications The mobile equipmentmay be further sub-divided into several entities, e.g the one which performs the radio transmission and

related functions, Mobile Termination, (MT), and the one which contains the end-to-end application or (e.g laptop connected to a mobile phone), Terminal Equipment, (TE).

USIM Domain

The USIM contains data and procedures which unambiguously and securely identify itself Thesefunctions are typically embedded in a standalone smart card This device is associated to a given user,and as such allows to identify this user regardless of the ME he uses

Infrastructure Domain

The Infrastructure domain is further split into the Access Network Domain, which is characterized

by being in direct contact with the User Equipment and the Core Network Domain This split is

intended to simplify/assist the process of de-coupling access related functionality from non-accessrelated functionality and is in line with the modular principle adopted for the UMTS The Access NetworkDomain comprises roughly the functions specific to the access technique, while the functions in the Corenetwork domain may potentially be used with information flows using any access technique This splitallows for different approaches for the Core Network Domain, each approach specifying distinct types

of Core Networks which can be connected to the Access Network Domain, as well as different accesstechniques, each type of Access Network connected to th Core Network Domain The reference pointbetween the access network domain and the core network domain is termed the "lu" reference point

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UMTS Domains Version 1 Rev 0

UMTS Domains

HomeNetworkDomain

TransitNetworkDomain

ServingNetworkDomain

CoreNetworkDomain

AccessNetworkDomain

MobileEquipmentDomain

USIM

Domain

InfrastructureDomain

User EquipmentDomain

Uu

[Zu]

CuSIM

CARD

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Access Network Domain

The Access Network Domain consists of the physical entities which manage the resources of the accessnetwork and provides the user with a mechanism to access the core network domain

Core Network Domain

The Core Network Domain consists of the physical entities which provide support for the networkfeatures and telecommunication services The support provided includes functionality such as themanagement of user location information, control of network features and services, the transfer(switching and transmission) mechanisms for signalling and for user generated information

The core network domain is sub-divided into the Serving Network Domain, the Home Network Domain and the Transit Network Domain The reference point between the serving network domain and the

home network domain is termed the [Zu] reference point The reference point between the servingnetwork domain and the transit network domain is termed the [Yu] reference point

Serving Network Domain

The serving network domain is the part of the core network domain to which the access network domainthat provides the user's access is connected It represents the core network functions that are local to theuser's access point and thus their location changes when the user moves The serving network domain

is responsible for routing calls and transport user data/information from source to destination It has theability to interact with the home domain to cater for user specific data/services and with the transit domainfor non-user specific data/services purposes

Home Network Domain

The home network domain represents the core network functions that are conducted at a permanentlocation regardless of the location of the user's access point The USIM is related by subscription to thehome network domain The home network domain therefore contains at least permanently user specificdata and is responsible for management of subscription information It may also handle home specificservices, potentially not offered by the serving network domain

Transit Network Domain

The transit network domain is the core network part located on the communication path between theserving network domain and the remote party If, for a given call, the remote party is located inside thesame network as the originating UE, then no particular instance of the transit domain is activated

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UMTS Domains Version 1 Rev 0

UMTS Domains

HomeNetworkDomain

TransitNetworkDomain

ServingNetworkDomain

CoreNetworkDomain

AccessNetworkDomain

MobileEquipmentDomain

USIM

Domain

InfrastructureDomain

User EquipmentDomain

Uu

[Zu]

CuSIM

CARD

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The diagram opposite illustrates the basic configuration of a Public Land Mobile Network (PLMN)

supporting UMTS and GSM/GPRS This architecture is as defined in Release 1999 of the 3GPP (Dec02) specifications (TS23.002)

The Core Network (CN) Entities

The CN is constituted of a Circuit Switched (CS) domain and a Packet Switched (PS) domain These

two domains differ by the way they support user traffic, as explained below These two domains areoverlapping, i.e they contain some common entities A PLMN can implement only one domain or bothdomains

CS Domain

The CS domain refers to the set of all the CN entities offering "CS type of connection" for user traffic aswell as all the entities supporting the related signalling A "CS type of connection" is a connection forwhich dedicated network resources are allocated at the connection establishment and released at theconnection release The entities specific to the CS domain are:

• MSC - The Mobile-services Switching Centre

• GMSC - Gateway Mobile Service Switching Centre

• VLR - Visitor Location Register

PS Domain

The PS domain refers to the set of all the CN entities offering "PS type of connection" for user traffic

as well as all the entities supporting the related signalling A "PS type of connection" transports theuser information using autonomous concatenation of bits called packets: each packet can be routedindependently from the previous one The entities specific to the PS domain are the GPRS specificentities, i.e

• SGSN - Serving GPRS Support Node

• GGSN - Gateway GPRS Support Node

Entities Common to the CS and PS domains

The following entities are common provide common functions to the CS and PS Domains:

• HLR - The Home Location Register

• AUC - Authentication Centre

• EIR - Equipment Identity Register

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UMTS Architecture - Release 1999 Version 1 Rev 0

UMTS Architecture - Release 1999

HLR

EIR

SGSN VLR

MSC

VLR MSC

SIM

ME USIM

C

Gi

Gs

GfF

GE

lub

RNS RNS

BSS

SIM-ME I/f

or

MSCu

Uu

IuPSIuCS

A

Iur

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The Access Network (AN) Entities

Two different types of access network are used by the CN: the Base Station System (BSS) and the

Radio Network System (RNS) The BSS offers a Time Division Multiple Access(TDMA) based technology to access the Mobile Station whereas the RNS offers a Wideband-Code Division Multiple

Access (W-CDMA) based technology The MSC (resp SGSN) can connect to one of these AccessNetwork type or to both of them

The Base Station System (BSS)

The Base Station System (BSS) is the system of base station equipments (transceivers, controllers,

etc ) which is viewed by the MSC through a single A-interface as being the entity responsible forcommunicating with Mobile Stations in a certain area Similarly, in PLMNs supporting GPRS, the BSS

is viewed by the SGSN through a single Gb interface The functionality for the A interface is described

in GSM 08.02 and for the Gb interface in TS 23.060 The radio equipment of a BSS may support one ormore cells A BSS may consist of one or more base stations Where an Abis-interface is implemented,

the BSS consists of one Base Station Controller (BSC) and one or more Base Transceiver Station

(BTS)

The Radio Network System (RNS)

The Radio Network System (RNS) is the system of base station equipments (transceivers, controllers,

etc ) which is viewed by the MSC through a single Iu-interface as being the entity responsible forcommunicating with Mobile Stations in a certain area Similarly, in PLMNs supporting GPRS, the RNS

is viewed by the SGSN through a single Iu-PS interface The functionality for the Iu-CS interface isdescribed in TS 25.410 and for the Iu-PS interface in TS 23.060 The radio equipment of a RNS maysupport one or more cells A RNS may consist of one or more base stations The RNS consists of one

Radio Network Controller(RNC) and one or more Node B

The Mobile Station (MS)

The mobile station consists of the physical equipment used by a PLMN subscriber; it comprises the

Mobile Equipment (ME) and the Subscriber Identity Module (SIM), called User Services Identity

Module (USIM) for Release 99 and following releases The ME comprises the Mobile Termination (MT) which, depending on the application and services, may support various combinations of Terminal

Adapter (TA) and Terminal Equipment (TE) functional groups These functional groups are described

in GSM 04.02

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UMTS Architecture - Release 1999 Version 1 Rev 0

UMTS Architecture - Release 1999

HLR

EIR

SGSN VLR

MSC

VLR MSC

SIM

ME USIM

C

Gi

Gs

GfF

GE

lub

RNS RNS

BSS

SIM-ME I/f

or

MSCu

Uu

IuPSIuCS

A

Iur

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The diagram opposite shows a simplified schematic of a Release 1999 UMTS Network It illustrates onlythose entities associated with providing a UMTS service (i.e excludes any entities specifically associatedwith GSM/GPRS)

Entities of the CN-CS Domain

The Mobile Services Switching Centre (MSC)

The Mobile-services Switching Centre (MSC) constitutes the interface between the radio system and

the fixed networks The MSC performs all necessary functions in order to handle the circuit switchedservices to and from the mobile stations In order to obtain radio coverage of a given geographical area,

a number of base stations are normally required; i.e each MSC would thus have to interface severalbase stations In addition several MSCs may be required to cover a country The Mobile-servicesSwitching Centre is an exchange which performs all the switching and signalling functions for mobilestations located in a geographical area designated as the MSC area The main difference between aMSC and an exchange in a fixed network is that the MSC has to take into account the impact of theallocation of radio resources and the mobile nature of the subscribers and has to perform proceduresrequired for the location registration (see TS 23.012) and procedures required for handovers (see TS23.009)

The Gateway MSC (GMSC)

If a network delivering a call to the PLMN cannot interrogate the HLR, the call is routed to an MSC ThisMSC will interrogate the appropriate HLR and then route the call to the MSC where the mobile station

is located The MSC which performs the routing function to the actual location of the MS is called the

Gateway MSC(GMSC) The acceptance of an interrogation to an HLR is the decision of the operator.The choice of which MSCs can act as Gateway MSCs is for the operator to decide (i.e all MSCs orsome designated MSCs)

The Visitor Location Register (VLR)

A mobile station roaming in an MSC area is controlled by the Visitor Location Register (VLR) in charge

of this area When a Mobile Station (MS) enters a new location area it starts a registration procedure.

The MSC in charge of that area notices this registration and transfers to the VLR the identity of thelocation area where the MS is situated If this MS is not yet registered, the VLR and the HLR exchangeinformation to allow the proper handling of calls involving the MS A VLR may be in charge of one orseveral MSC areas The VLR contains also the information needed to handle the calls set-up or received

by the MSs registered in its database The following elements are included:

• The International Mobile Subscriber Identity (IMSI);

• The Mobile Station International ISDN number (MSISDN);

• The Mobile Station Roaming Number (MSRN), see TS 23.003 for allocation principles;

• The Temporary Mobile Station Identity (TMSI), if applicable;

• The Local Mobile Station Identity (LMSI), if used;

• The location area where the mobile station has been registered;

• The last known location and the initial location of the MS

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UMTS Network - Release 1999 Version 1 Rev 0

UMTS Network - Release 1999

Node B Node B

RNCUTRAN

Node B Node B

RNC

HLRVLR AuCGMSC

OMC-U(UTRAN)

Iur

Uu

User Equipment

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Entities Common to the CS and PS Domains

The Home Location Register (HLR)

This functional entity is a database in charge of the management of mobile subscribers A PLMN maycontain one or several HLRs: it depends on the number of mobile subscribers, on the capacity of theequipment and on the organisation of the network The following kinds of information are stored there:

• Subscription information

• Location information enabling the charging and routing of calls towards the MSC where the MS

is registered (e.g the MS Roaming Number, the VLR Number, the MSC Number, the Local MSIdentity)

• If GPRS is supported, location information enabling the charging and routing of messages in theSGSN where the MS is currently registered (e.g the SGSN Number)

• The types of identity are attached to each mobile (e.g International Mobile Station Identity (IMSI), one or more Mobile Station International ISDN Number(s) (MSISDN), if GPRS is supported zero or more Packet Data Protocol (PDP) address(es)).

The Authentication Centre (AuC)

The Authentication Centre (AuC) is an entity which stores data for each mobile subscriber to allow the International Mobile Subscriber Identity (IMSI) to be authenticated and to allow communication

over the radio path between the mobile station and the network to be ciphered The AuC transmits thedata needed for authentication and ciphering via the HLR to the VLR, MSC and SGSN which needs

to authenticate a mobile station The Authentication Centre (AuC) is associated with an HLR, and

stores an identity key for each mobile subscriber registered with the associated HLR This key is used

to generate:

• Data which are used to authenticate the International Mobile Subscriber Identity (IMSI).

• A key used to cipher communication over the radio path between the mobile station and the network

The Equipment Identity Register (EIR)

The Equipment Identity Register (EIR) in the GSM system is the logical entity which is responsible for storing in the network the International Mobile Equipment Identities (IMEIs), used in the GSM system.

The equipment is classified as "white listed", "grey listed", "black listed" or it may be unknown as specified

in TS 22.016 and TS 29.002

This functional entity contains one or several databases which store(s) the IMEIs used in the GSMsystem An EIR shall as a minimum contain a "white list" (Equipment classified as "white listed") Seealso TS 22.016 on IMEI

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UMTS Network - Release 1999 Version 1 Rev 0

UMTS Network - Release 1999

Node B Node B

RNCUTRAN

Node B Node B

RNC

HLRVLR AuCGMSC

OMC-U(UTRAN)

Iur

Uu

User Equipment

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In R4 the separation of the switching and call control functions within the core network is commonlyreferred to as a softswitch architecture The call control component, i.e the MSC server, is the softswitch

in this case This separation of functions makes it easier to scale the network as the traffic demandincreases If the network planners require more switching capacity they can add MGWs; if they requiremore call control capacity they then add more MSC servers This is a clear distinction from the UMTSRelease 99 and GSM networks, in which the call control and switching functions are all carried out withinthe MSC and gateway MSC (GMSC)

Media Gateways (MGWs)

This translates media traffic between different types of network Functionality carried out by the MGWincludes:

• Termination of bearer channels from the circuit switched and packet switched networks;

• Echo cancellation for circuit switched circuits;

• Translation of media from one CODEC form to another,

Each MGW is controlled by one or more MSC servers

MSC Server

This performs functions such as call control for mobile-originated and mobile-terminated calls, andmobility management in terms of maintenance of the registry of mobiles within its area of control The

MSC server integrates with the Visitor Location Register (VLR) component, which holds location

information as well as CAMEL (customized applications for mobile network enhanced logic) data forsubscribers Functions carried out by the MSC server include:

• Controlling the registration of mobiles to provide mobility management;

• Providing authentication functions;

• Routing mobile-originated calls to their destination;

• Routing mobile-terminated calls by using paging to individual mobiles

The MSC server terminates signalling from the mobile network over the Iu interface to the RNC It alsocontrols the establishment of bearers across its core by the use of MGWs under its control

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UMTS Network R4 Version 1 Rev 0

A

Gb ABIS

Iub

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Release 5(R5) builds on the partial implementation of IP packet switching within the core network, tomove to an all-IP architecture In this release, packets can be moved end-to-end using IP transport with

an enhanced GPRS network connected to an IP multimedia subsystem (IMS) The GPRS backbone

for R5 must be able to provide similar levels and classifications of QoS usually associated with ATMnetworks This is to allow for the delivery of time-sensitive traffic such as voice and multimedia As well

as enhancements to the core network, the RAN also migrates from ATM to IP Even though the visionfor R5 is for a total IP solution, the operator may well still use ATM as a transport solution for some parts

of the network This is possible because all UMTS releases must provide backward compatibility withearlier releases

Notice that in the R5 network, the CS domain can be dispensed with since the services associatedwith it, such as transfer of voice traffic, can be carried over the GPRS and IMS networks using IP QoSmechanisms That given, many operators may still be using the R4 CS domain as well as the R5 IMSarchitecture This allows for a gradual migration to an all-IP architecture with the minimal disruption

to service Some voice calls may be handled using the CS domain and some, for example video callservices, via the IMS

IP MULTIMEDIA SUBSYSTEM (IMS)

R5 introduces a new network domain called the IP Multimedia Subsystem (IMS) This is an IP network

domain designed to provide appropriate support for real-time multimedia services

The UE communicates with the IMS using GPRS, with the IMS being directly connected to the GGSN.The IMS provides services to mobile users such as:

• Real-time communication using voice, video or multimedia messaging (i.e voice and videotelephony);

• Audioconferencing and videoconferencing;

• Content delivery services such as video, audio or multimedia download;

• Content streaming services such as video, audio or multimedia streaming (e.g using video ondemand server);

• Multimedia Messaging Service(MMS)

Each operator’s IMS can be connected to other operators’ IMSs, allowing multimedia services betweenusers on different networks Connections to the public Internet allow MMS messaging as well as voiceover IP (VoIP) and video telephony between mobile and fixed-line users Finally, the interface to the ISDN(or other circuit switched networks) allows VoIP calls to be connected through to conventional fixed-lineand mobile users, e.g GSM Connections between the IMS and other IP networks are controlled byfirewalls to protect against hacking The interface between the IMS and the CS network is controlled by

the softswitch and MGW components Within the operator’s network the IMS is connected to the Home

Subscriber Server(HSS) to allow for subscriber authentication, authorization and mobility management.For R5 and beyond, the IMS can be used to provide transport for all of the operator’s services, includingconventional voice calls

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UMTS Network Release 5 Version 1 Rev 0

UMTS Network Release 5

Iub

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The UTRAN consists of a set of Radio Network Subsystems (RNSs) connected to the Core Network through the IuCS and IuPS A RNS consists of a Radio Network Controller (RNC) and one or more

Node Bs A Node B is connected to the RNC through the Iub interface A Node B can support FDD mode,TDD mode or dual-mode operation The RNC is responsible for the Handover decisions that requiresignalling to the UE An RNC may include a combining/splitting function to support combination/splitting

of information streams

Inside the UTRAN, the RNCs of the Radio Network Subsystems can be interconnected together throughthe Iur Iu(s) and Iur are logical interfaces Iur can be conveyed over direct physical connection betweenRNCs or virtual networks using any suitable transport network

• System information broadcasting

Radio channel ciphering and deciphering

Functions related to mobility

• Handover

• SRNS Relocation

Functions related to radio resource management and control

• Radio resource configuration and operation

• Radio environment survey

• combining/splitting control

• Radio bearer connection set-up and release (Radio Bearer Control)

• Allocation and deallocation of Radio Bearers

• Radio protocols function

• RF power control

• RF power setting

• Radio channel coding/decoding

• Channel coding control

• Initial (random) access detection and handling

• CN Distribution function for Non Access Stratum messages

Functions related to broadcast and multicast services

NOTE: Only Broadcast is applicable for Release 1999

• Broadcast/Multicast Information Distribution

• Broadcast/Multicast Flow Control

• CBS Status Reporting

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UMTS Terrestrial Radio Access Network (UTRAN) Version 1 Rev 0

UMTS Terrestrial Radio Access Network (UTRAN)

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A Radio Network Controller (RNC) is a network component within the PLMN with the functions to

support one or more Node B, Cell and/or User Equipment

Typically one RNC can support up to 300 Node Bs, which in turn can provide resources for up to 6 cells.However, it should be noted that the ultimate limiting factor in planning the number of RNCs requiredwithin a PLMN will be the traffic capacity that the RNC can support Typical values will start at around

1000 Erlang, rising to 10,000 Erlang as networks mature

A Radio Network Controller (RNC) can be considered to operate in one or more of the following roles:

• Controlling Radio Network Controller(CRNC)

• Serving Radio Network Controller(SRNC)

• Drift Radio Network Controller(DRNC)

Controlling Radio Network Controller (CRNC)

Controlling RNC is a role an RNC can take with respect to a specific set of Node B's There is only oneControlling RNC for any Node B The Controlling RNC has the overall control of the logical resources ofits node B's

The main functions of a CRNC are:

• Control of the Radio Resources for the Node-B it controls

• Provision of Services to the Node-B that it controls

• Load and Congestion Control

• Admission Control

• Code allocation for new radio links

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Radio network Controller (RNC) Version 1 Rev 0

Radio network Controller (RNC)

UTRAN CRNC Functions

Controlling of the Radio Resources Provision of Services to the Node-B Load and Congestion Control Admission Control

Code Allocation for new Radio Links

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Serving Radio Network Controller (SRNC)

A Serving RNC is the RNC located within a Serving RNS (SRNS) SRNS is a role an RNS can take with

respect to a specific connection between an UE and UTRAN

There is one Serving RNS for each UE that has a connection to UTRAN

The Serving RNS is in charge of the radio connection between a UE and the UTRAN

The Serving RNS terminates the Iu for this UE

The main functions of an SRNC are:

• Termination of the Radio Resource Control Signalling between the RNC and the UE

• L2 Processing (PDCP, RLC, MAC)

• Radio Resource Control operations

• Mapping of Iu Bearer Parameters onto Transport Channels Parameters

• Hand-over decisions

• Outer loop power control

• Macro-Diversity combining and splitting

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UTRAN SRNC Functions

Termination of the Radio Resource Control Signalling between the RNC and the UE

L2 Processing (PDCP, RLC, MAC) Radio Resource Control Operations Mapping of Bearer Parameters onto Transport Channel Parameters

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Drift Radio Network Controller (DRNC)

A Drift RNC is located within a Drift RNS DRNS is role that an RNS can take with respect to a specificconnection between a UE and UTRAN

A DRNS is any RNS that supports the Serving RNS by providing radio resources via the cell(s) it controls,

to provide additional radio bearer services for a specific connection between a UE and UTRAN

There may be zero, one or more DRNSs associated with a specific connection between a UE andUTRAN

The main functions of a DRNC are:

• Macro-diversity combining and splitting

• No L2 processing, i.e no re-transmissions, acknowledgements or negative acknowledgements

• Transparent routing of data on the Iub and Iur Interfaces, except when Common or shared channelsare used

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UTRAN DRNC Functions

Macro-diversity Combining and Splitting

No L2 Processing Transparent Routing except for Common/Shared Channels

·

D-RNC S-RNC

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On completion of this chapter the student should be able to:

• Describe various options for multiple access schemes

• State the Characteristics of UMTS W-CDMA

• State why W-CDMA has been chosen for the UMTS multiple access scheme

• Describe W-CDMA spreading and despreading procedures

• Describe the use of orthagonal codes and the channelisation code tree

• Describe the scrambling and summation process

• Describe the effects of multi-path radio channels and the purpose of the RAKE receiver

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Version 1 Rev 0 Multiple Access Schemes

Multiple Access Schemes

There are 3 forms of multiple access schemes, frequency, time and code The major issue with the firsttwo is the requirement to have guard bands

Frequency Division Multiple Access (FDMA)

FDMA divides radio channels into a range of radio frequencies and is used in the traditional analoguesystem With FDMA, only one subscriber is assigned to a channel at one time Other subscribers cannotaccess this channel until the original call is terminated or handed off to a different channel

Time Division Multiple Access (TDMA)

TDMA is a common multiple access technique employed in digital cellular systems It divides radiochannels into time slots to obtain higher capacity As with FDMA, no other conversations can access anoccupied channel until that channel is vacated

Code Division Multiple Access (CDMA)

CDMA assigns each subscriber a unique code to put multiple users on the same channel at the sametime CDMA users can share the same frequency channel because their conversations are distinguishedonly by digital code

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Time

Frequency

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Version 1 Rev 0 W-CDMA Characteristics

W-CDMA Characteristics

The vital statistics for our W-CDMA UMTS system is shown opposite Don't be confused by the slotsand frames, this is not a TDMA system, every user does share the same band The frames and slotsare used for interleaving, power control

The major points are:

FDD requires paired frequencies for up and down channels

The chip rate of 3.84 Mcps provides a bandwidth of 5 MHz A chip is the original signal split or chipped

by the spreading code

The carrier spacing of 200 kHz is used to allow re-farming of GSM frequencies which have been set at

The user data rates available in the FDD system is up to 384 Kbps

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Multiple Access Scheme Duplexing Method Chip Rate

Bandwidth Carrier Spacing Frame Length Slots per Frame Inter-cell Synchronization Spreading Factor

User Data Rate

CDMA FDD 3.84 Mcps

5 MHz

200 kHz Raster

10 ms 15 None Variable (4-512) 3-384 Kbps

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Version 1 Rev 0 Re-Use of Frequency

Re-Use of Frequency

Mobile telephones and cell broadcast networks use cellular radio, a technique developed in recent years

to enable the use of mobile telephones It would be impossible to provide each phone with an individualradio frequency, so the idea of cellular radio evolved

A region is divided into geographical areas called cells, varying in size depending on the number of users

in the area In cities cells are small whereas in rural areas cells are much larger

In GSM cells use a set of frequencies that are different from any neighbouring cell, but can be the same

as another cell as long as it is far enough away

For UMTS, a frequency re-use of one, may be employed This means that all cells within a givengeographical area, or even an entire network may use the same carrier frequency

An alternate method of discriminating between neighbouring cells must therefore be found

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25

3

74

25

3

74

25

1

2

57

4

6

3

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Version 1 Rev 0 Re-Use of Codes

Re-Use of Codes

Codes are used to uniquely identify a cell in the network Frequency planning is more or less a thing

of the past but code planning will have to be implemented Code planning will be much easier thenfrequency planning since we have 512 Codes to play with, the code re-use pattern will thus be extremelylarge

Codes can be reused when the separation between cells containing the same channel set is far enoughapart so that co-channel interference can be kept below acceptable levels The number of cells in acluster is 512, which provides greater separation between co-channel cells than GSM

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14 6

16 15

29

2 25

41

24

5 33

40 26

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Version 1 Rev 0 Spectral Efficiency (GSM and UMTS)

Spectral Efficiency (GSM and UMTS)

The Slide opposite shows how spectrally efficient UMTS and GSM is in comparison to each other whenemployed in a multi-cellular structure

The capacity, which Shannon derived in 1947, provided a Law, which we now call Shannons Law Thisdetails the digital capacity of the link given the transmit power and the bandwidth

If we are using, FDMA, TDMA or CDMA, the capacity is still controlled by this law However, some gainsare made by technology and coding methods

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7 x 200 kHz = 1.4 MHz

1 Call = 25 kHz

8 Calls = 200 kHz Carrier

1 Call = 25 kHz GSM

7 Cells, 5 MHz

1 Call = 2.8 kHz

256 Calls = 5 MHz Carrier

1 Call = 19.4 kHz UMTS

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Version 1 Rev 0 Direct Spread (DS)-CDMA Implementation

Direct Spread (DS)-CDMA Implementation

Transmitter

The digital modulator will take digital speech/data and multiply it with the spreading code

The radio modulator moves the baseline signal from the digital modulator onto a 2GHz carrier to producethe W-CDMA output

Receiver

The modulated carrier is moved by the radio demodulator to the digital demodulator which can be verycomplicated due to the large number of users

Here the input is multiplied by the de-spreading codes to produce digital speech

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Single User Channel

5 MHz

Multiple User Channel

5 MHz Multiple User Channel

Digital Signal

Spreading Code Generator

Digital Modulator

Radio Modulator C

o m b i n e r

S p l i t t e r

Digital Signal

Digital Demodulator Radio

Demodulator

Radio Demodulator

Digital Demodulator

t0

Rx

Radio Carrier

Tx

W-CDMA Modulated Carrier

Spreading Code Generator

USR7

Định dạng
Số trang	77
Dung lượng	1,94 MB