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Chapter 7. W-CDMA Technology



1. UMTS Network

1.1. IMT-2000 Interfaces

The W-CMA system consists of a number of logical network elements that each has a defined

functionally. In the standards, network elements are defined at the logical level, but this

quite often results in a similar physical implementation, especially since there are a number

of open interfaces. The network elements can be grouped into Radio Access Network (RAN)

that handles all radio-related functionally, and the external networks. To complete the

system, the User Equipment (UE) that interfaces with the user and the radio interfaces

defined.

Radio Access Network (RAN) is a switched circuit network consisting of Radio Network

Controller and Node B. It is linked to Core Network via Iu interface. In 3GPP, RAN is

referred to as UTRAN. RNC is the radio controller which manages radio resources and

controls Node B, and controls handover, for example.

Node B, a logical node which receives and transmits radio signals, is the base station in the

real world.



IMT-2000 Interfaces

Radio Interface ; W-CDMA (IMT-DS)

Network Interface; GSM Evolved

Radio AccessNetwork

Core Network

UENode

-BRNC

(BSC) MSC GMSC

Other

Networks

Serv ice/Mobility

Control

Radio Interface

(UE-RAN)

Fig. 7.1 IMT-2000 Interface



1.2. UMTS System Components

The interface between Node B and RNC is referred to as I ub, and the interface between

RNC’s is I ur. Node B covers one or more cells. When one base station is sectorized andequipped with multiple directional antennas, each sector is sometimes called cell.

Node B is connected with mobiles via radio interface.

Network Elements

Core Network

GMSC: Gateway Mobile Services Switching Center

Switches circuit switched (CS) data to the external network.

MSC: Mobile Services Switching Center

Switches circuit switched (CS) data.

VLR: Visitor Location Register

Stores copy of visiting user’s service profiles.

HLR: Home Location Register

Stores user’s service profiles.

GGSN: Gateway GPRS Support Node

Handles packet switched (PS) data to the external network.

SGSN: Serving GPRS Support Node

Handles packet switched (PS) data.

UTRAN

RNC: Radio Network Controller

Controls radio resources.

Node-B

Converts Data flow between Iub and Uu interface.

UE

ME: Mobile Equipment

Radio terminal used for radio communication.

USIM: UMTS Subscriber Identity Module

Smart card that stores subscriber identity.



Fig. 7.2 UMTS System Architecture

UTRAN

RNS

RNS

UE

UMTS System ArchitectureNetwork Elements in PLMN

CN

USIMUSIM

MEME

Node-B

Node-B

Node

-B

Node

-B

RNCRNC

Node-B

Node-B

Node-B

Node-B

RNCRNC

Uu

CuIur

Iu

UTRAN : UMTS Terrestrial radio access network RNS : Radio network sub-system

UE : User equipment

Iub

PSTN

ISDN

Internet

MSC

/VLR

MSC

/VLR

SGSNSGSN

GMSCGMSC

GGSNGGSN

HLRHLR

UMTS: Universal Mobile Telecommunication Service

PLMN: Public Land Mobile Network



2. Cell size and duplex technology

CDMA communication technology proposed to ITU-R includes TDD and FDD. TDD switches

alternatively between up and down links at certain time intervals on the same frequency. I t is

suited for metropolitan centers with high traffic.

FDD uses different frequencies for up and down links for transmission. FDD can further be

divided into FDD-DS and FDD-MC.

In FDD-DS, one carrier is respectively employed for up and down links.

In FDD-MC, one carrier is used for uplink but multiple carriers for downlinks. It is suited for

service in micro-cells.

In W-CDMA system mainly FDD is used and TDD is used for Pico cell high traffic spot area.



Fig. 7.3 Macro/Micro/Pico Cells

Fig. 7.4 W-CDMA Coverage

T r a f f i c

Area

avg traffic

hot spottraffic

FDD (Frequency Division Duplex):macro/micro cells in entireentire service areaservice area

TDD (Time Division Duplex):

micro/pico cells in hot spotshot spots

FDD Macro CellFDD Macro Cell

FDDMicro Cell

FDDMicro Cell

TDDMicro Cell

TDDMicro Cell

TDDPico Cell

TDDPico Cell

Macro/Micro/Pico Cells

Inter-Network Roaming (Seamless end-to-end Service)

Audio/visualTerminals

• public macro and microcell environments

• up to 384 Kbps (Mobile)

• up to 2 Mbps (Indoor)

Satellite

Global

Suburban Urban

In- Building

PicoPico--CellCell

MicroMicro--CellCell

MacroMacro--CellCellHome-Cell

TDD TDD

• pico cellenvironments

• Asymmetricalaccess

• up to 2 Mbps

FDDFDD

W-CDMA Coverage



2.1. FDD

Characteristics of FDD

•

A pair of frequencies are required for up and down links.• Transmission power may be held low due to continuous transmission.

• Operable with unsynchronized radio stations.

2.2. TDD

Both up and down links are on the same frequency, but are segregated by timing. In this

example shown here, uplink signal is 1 when downlink signals are 14.

Characteristics of TDD

• Even an isolated frequency band can be used.

• Slots can be allocated freely for up and down links, transmission is effective when

volumes of information coming and going on up and down links differ.

• Synchronization is required between radio station to avoid interference.

• Transmission power tends to be high due to burst transmission, and propagation

latency needs to be controlled within the inter-slot guard time, which makes it

difficult to cover wide areas with this technology.



Downlink

Uplink

max 256

cont.

Frequency

5 MHz

Time10 ms0 ms

0

Code

max 256

cont.

Frequency

5 MHz

Time10 ms0 ms

0

Code

FDD Principle

Pair Link

f 1f 1

f 2f 2

Difference

Frequency

Fig. 7.5 FDD Principle

14: 1

2:13

Uplink ( )

max 16Frequency

5 MHz

Time

667µs0 ms

0

Code

10 ms

TDD Principle

Asymmetry

14:1.... 2:13

Up or Downlink( )

Downlink ( )

15 time slots &

max. 16 orthogonal

codes per time slot

f 1f 1

Fig. 7.6 TDD Principle



2.3. Spectrum allocation

Either FDD or TDD can be used for W-CDMA.

The specific frequency bands are specified for each of them, as shown in the chart.



Fig. 7.7 Spectrum Allocation for UMTS

20 +15 MHz for

unpaired TDD

20 +15 MHz for

unpaired TDD60 + 60 MHz for

paired FDD

60 + 60 MHz for

paired FDD

UMTS satellite

1850 1900 1950 2000 2050 2100 2150 2200 2250

20 60 30 15 60 30

MHz

GSM 1800

UMTS FDD

Spectrum Allocation for UMTS

UMTS TDD

FDD : Frequency division duplex

TDD : Time division duplexUMTS : Universal mobile telecommunication service



3. Radio Channel Layer

Logical channels are divided by functions of transmitted signals and logical attributes, and

are differentiated by the contents of the transmitted information.

MAC interfaces the Transport Channel with this logical channel and Layer 1

There are multiple types of transport channels to transmit data with different attributes and

different modes of transmission over the physical layer.

Physical channels are determined by codes and frequencies in FDD mode.

Radio interface protocol architecture is comprised of Physical Layer (L1), data Link L ayer

(L2) and Network Layer (L3) protocol. I t is also made up of C Plane for signaling control

signal transmission and U Plane which transfers subscriber data. PDCP on Layer 2 applies

only to U Plane. Layer 3 consists of RRC which terminates at RAN, and higher layers.



Fig. 7.8 Radio Channel Layers in UMTS

Fig. 7.9 Radio Channel Layers in UMTS

Radio Channel Layers in UMTS

UE

MACMAC

IubNode-B RNC CN

Transport ChannelTransport ChannelPhysical ChannelPhysical Channel

DedicatedDedicatedDedicated

ChannelChannelChannel

CommonCommonCommon

ChannelChannelChannel

Logical ChannelLogical Channel

TrafficTrafficChannelChannel

ControlControlChannelChannel

TrafficTrafficChannelChannel

ControlControlChannelChannel

IuUu

MAC: Medium access control


Radio Channel Layers in UMTS

L2

L3

IubNode-B RNC CN

Iu

RRC

PDCP

RLC

Control Plane User Plane

RRC (Radio Resource Control Protocol)

¾Transfers control signaling data.PDCP (Packet Data Convergence Protocol)¾Transfers user data for Packet Switching.

¾Compresses of redundant protocol

information.

RLC (Radio Link Control Protocol)¾Transfers upper layer data.

¾Controls data transferring.

RRC (Radio Resource Control Protocol)¾

Transfers control signaling data.PDCP (Packet Data Convergence Protocol)¾Transfers user data for Packet Switching.

¾Compresses of redundant protocol

information.

RLC (Radio Link Control Protocol)

¾Transfers upper layer data.

¾Controls data transferring.

CC/MMPacket

Data

Voice

Data

CC : Call control

MM : Mobile management



4. W CDMA Air Interface

4.1. Air Interface

This chart shows the air interface protocol in the W-CDMA system. The protocol consists of

Physical Layer (Layer 1), Data Link Layer (Layer 2) and Network Layer (Layer 3).

Channels in the air interface comprise three layers, i.e., Physical Channel, Transport

Channel and Logical Channel, to accommodate flexibly various service modes and multiple

calls.

Mapping of Physical Channel to Transport Channel is performed in MAC Sub layer, and

mapping of Transport Channel to Physical Channel in Physical Layer.

4.2. Radio Channel

By multiplexing multiple transport channels on physical channels, it is made possible to

multiplex mobile data and control data, and data for multiple mobiles in multi-calls.

DPCH in the Physical channel consists of DPDCH and DPCCH, where DPCCH is the channel

that transmits data and DPCCH, subservient to DPDCH, controls Layer 1, e.g., control of

transmit power.

• Logical Channel

DTCH (Dedicated Traffic Channel)Transfers user information to 1 User Equipment (UE).

DCCH (Dedicated Control Channel)

Transfers control information to 1 User Equipment (UE).

CTCH (Common Traffic Channel)

Transfers user information to all or group User Equipments (UEs).

PCCH (Paging Channel)

Transfers paging information.

BCCH (Broadcast Channel)

For broadcast system control information.

CCCH (Common Control Channel)

Transfers control information between network and User Equipments.

MAC (Medium Access Control) Layer

Converts logical channels and transport channels.



Fig. 7.10 W-CDMA Air Interface

L1

W-CDMA Air Interface

Radio Channels

Physical ChannelPhysical Channel

Transport ChannelTransport Channel

MACMACMAC

MAC: Medium access control


Upper Layer Upper Layer Upper Layer This channel is used for This channel is used for This channel is used for

logical processing in thelogical processing in thelogical processing in the

UMTS.UMTS.UMTS.

This channel is used for This channel is used for This channel is used for transportation betweentransportation betweentransportation between

logical and physicallogical and physicallogical and physical

channels.channels.channels.

This channel is physicallyThis channel is physicallyThis channel is physically

transmitted on the radio.transmitted on the radio.transmitted on the radio.

L2



• Transport Channel

DCH (Dedicated Channel)

Transfers user or control information between the network and the UE.RACH (Random Access Channel)

Transfers control information from a UE.

CPCH (Common Packet Channel)

Transfers packet-based user data, it is an extension of RACH.

BCH (Broadcast Channel)

Broadcasts system and cell specific information.

FACH (Forward Access Channel)

Transfers control information to a UE.

PCH (Paging Channel)

Transfers paging information a UE.

DSCH (Downlink Shared Channel)

Transfers dedicated control or traffic data, it can shared several users.

• Physical Channel

DPDCH (Dedicated Physical Data Channel)

Transfers dedicated data generated at layer 2 and above.

DPCCH (Dedicated Physical Control Channel)

Transfers control information generated at layer 1.

DPCH (Downlink Dedicated Physical Channel)

Transfers control information to a UE.

PRACH (Physical Random Access Channel)

Transfers the RACH.

PCPCH (Physical Common Packet Channel)

Transfers the CPCH.

P-CCPCH (Primary Common Control Physical Channel)

Transfers the BCH.

S-CCPCH (Secondary Common Control Physical Channel)

Transfers FACH and PCH.

PDSCH (Physical Downlink Shared Channel)

Transfers DSCH.

CPICH (Common Pilot Channel)

Supplies down physical channel default phase.

SCH (Synchronization Channel)Used for cell search.



Fig. 7.11 Radio Channels

PICH (Page Indication Channel)

Transfers the page indication.

AICH (Acquisition I ndication Channel)

Transfers acquisition indicator for PRACH access.

AP-AI CH (Access Preamble Acquisition Indication Channel)

Transfers acquisition indicator for PCPCH access.

CD/CA-ICH (CPCH Collision Detection/Channel Assignment Indicator Channel)

Used for coll ision control of PCPCH.

CSICH (CPCH Status Indicator Channel) Transfers status information of PCPCH.

Radio Channels

MAC

Transport

Channel

DPCCH

DPCH

PCPCH

AICH

Physical Channel

D e d i c a t e

C omm on C h ann el

U pL i nk

D own

L i nk

U

pL i nk

D ownL i nk

DPDCH

PRACH

P-CCPCH

S-CCPCH

PDSCH

CPICH

SCH

PICH

DCH

CPCHRACH

BCH

FACH

PCH

DSCH

T r af f i c

C on t r ol C h ann

el

Logical Channel

DTCH

DCCH

CTCH

CCCH

BCCH

PCCH

D e d i c a t e

C omm on C h ann el

U p &

D ownL i nk

U

pL i nk

D ownL i nk

U p &

D ownL i nk

D ownL i nk

U p / D own

D e d i c a t e

C omm on C h ann e

l

C on t r o

l T r af f i c

AP-AICH

CD/CA-ICH

CSICH

D own



5. System Structure

The chart illustrates the definition of each interface.

Signals and voice signals are transferred via ATM between Node B and CN.

W-CDMA system introduces AMR for voice coding. Voice data are coded and decoded at mobile

terminals in one end and CN in the other end.



Fig. 7.12 System Structure

System StructureNode Interface

Node-B

RNC CN

OMC-R

OMC-BOMC-S

Iub Interface:E1: 2 Mbps

(or STM1: 156 Mbps)

Iu Interface:STM1: 156 Mbps

ATM

UE

P Interface

Gi Interface

AMR (= Codec)

PSTNNo.7

Network

Internet

MSC, GMSC, SGSN, GGSN

AMR : Adaptive multi-rate

ATM : Asynchronous transfer modeOMC : Operation & maintenance center



5.1. ATM Interface

3rd Generation Mobile Communication demands switching technologies that is capable of

efficient transfer of compressed voice and increasing internet access data. ATM is atechnology that transmits and switches information in 53-byte frames (called cell). 3GPP

requires adoption of ATM in RAN. CN also has functions which ATM can best perform, such

as joint traffic control with RAN, accommodation of circuit switching and packet switching

within the same architecture, and general service quality and operation supervision.

ATM has capabilities of solid traffic and service quality control, and is a resourceful

technology for delivering not only circuit switching but packet switching services.



Fig. 7.13 ATM Interface

ATM Interface

Node-B

RNC

UE

ATM: Asynchronous transfer modeIP : Internet protocol

STM: Synchronous transfer mode

ATM

STM

GMSC,

GGSN

GMSC,GMSC,

GGSNGGSN

IP

MSC,

SGSN

MSC,

SGSN

CN

PSTNInternet

Iub Interface Iu Interface P/Gi Interface

ATM/STM (IP)ATM/STM (IP)

ConversionConversion



5.2. ATM Based CDMA Network

Voice and signals, after reception of radio signals is processed, are transferred to RNC in ATM

cells.Control signals are processed in RNC and control signals and data are forwarded to CN. ATM is

used for interface between CN and RNC, but CN is equipped with STM switch for interface

with STM network.

CL AD is used for conversion between ATM and STM.

For enhanced efficiency in transmitting signals, multiple data are packaged in one ATM cell,

hence referred to as a composite cell.



Fig. 7.14 ATM-based CDMA Network

ATM-based CDMA Network

CN

DTI

CDMA AAL2/AAL5 Composite Cell ATM

Node-B RNC

CLAD

IPGW

STM

Network

ATM

Network

Internet

AAL1 (AAL2)

ATM

Switch

ATM

Switch

DTISTM

Switch

AAL : ATM adaptive layer

CLAD: Cell assembly/disassembly

DTI : Digital transmission interface

IPGW: Internet protocol gateway



5.3. ATM Composite Cell

Each cell ordinarily is transferred with only one parcel of information, but ATM composite cells

are used for efficient data transmission.ATM composite cells are sent with multiple data packaged in one ATM cell.

AAL is a protocol which aligns the higher layer which has various traffic attributes as IP

packets, with the ATM layer which is fixed regardless of higher applications.

ALL2 has originally standardized for efficient transfer by ATM of such short frames as

high-efficiency voice signals used in mobile communication, and in IMT-2000 RAN, it is used as

a standard to transfer subscriber data.

AAL 5 is a simpler protocol as compared with AAl3/4, and is widely employed to transfer data

packets and control signals.



Fig. 7.15 ATM Composite Cell

Fig. 7.16 ATM-based CDMA Network

ATM Composite Cell

ATM Standard Cell

ATM Cell Header Payload

ATM Cell --AA

PAD

ATM Cell --BB ATM Cell --CC

ATM Composite Cell

ATM Cell Header Payload

ATM Cell --AA

User Data

a

ATM Cell --BB

User

Data

b2

User

Data

c

User

Data

b1

User Data

a

User Data

b

User

Data

c

PAD PAD

ATM-based CDMA Network

Future Evolution to

Seamless Multimedia Services

Future Evolution toFuture Evolution to

Seamless Multimedia ServicesSeamless Multimedia Services

Efficient/High-Performance Network for CDMAReal Time Small Volume Traffic ;Voice Traffic: AAL2 is applied

Other Traffic: AAL5 is applied

Real Time Large Volume Traffic ;AAL2, AAL5 or RTCP/IP over ATM

Non-Real Time Small/Large Volume TrafficPacket (Mainly TCP/IP) over ATM

RTCP : Real time transport control protocol

TCP : Transport control protocol



5.4. CODEC

I f communicating terminals have the same voice coding technology, there is no need for

decoding over the network, but voice signals coded at one terminal are conveyed over thenetwork to and decoded at the terminating terminal device.

In the mobile-to-fixed line communication, both ends have different voice coding scheme

(AMR and PCM in W-CDMA), and codec conversion is required within the network.

In W-CDMA systems, codec conversion is done at MSC.



Fig. 7.17 CODEC Control

Node-B

RNC

UE

GMSCGMSCMSCMSCMSC

CN

Iub Interface Iu Interface P Interface

CODEC Control

PCM SignalAMR Signal

AMR: Adaptive multi-rate PCM: Pulse code modulation

T r a f f i c

C h a

n n e l

PSTN(No.7 Network)

CodecCodec

ConversionConversion

AMR Signal (Codec Through)

Mobile – Land Call

Mobile – Mobile Call



5.5. Signaling System

RRC, the Layer 3 protocol for radio interface, advises UE of broadcast information between

UE and RNC, and conveys signals to set, change and release connections.Signaling to UE may be transmitted from Node B by way of Node B. In such cases, Iub

signals, such as NBAP, are used.

In terminating communication at PSTN, signals are converted into PSTN signals at MSC.

Signals are transferred up to GMSC by ATM, but from GMSC to PSTN, STM is used.

The chart shows an example of inter-node signaling and layer relationship.

E1 and STM-1 are used for physical layers between Node B and CN. All data (signals) are

transferred between Node B and CN by ATM. For network layer protocol, NBAP or RRC is

used between Node B and RNC, depending on the objectives.

Signals for connection with PSTN is No.7, and No.7 signals are transported in ATM cells

between MSC and GMSC, but are replaced onto STM signals at GMSC.



Fig. 7.18 Signaling System

Fig. 7.19 Signaling System

Node-B

RNC

UE

GMSCGMSCGMSCMSC,

SGSN

MSC,MSC,

SGSNSGSN

CN

Iub Interface Iu Interface P Interface

C o n t r

o l C h a

n n e l

PSTN(No.7 Network)

Signaling System

System Outline

PSTN : Public switched telephone network

RRC : Radio resource control

PSTN SignalingIu Signaling

Iub Signaling

RRC Signaling

(No.7 + ATM) (No.7 + STM)No.7+

STM or ATM

Signaling System

Protocol Stack (Layer)

MobileLayer 1

Physical Layer

ATM

NBAP

Physical Layer

ATM

Physical Layer

ATM

No.7 (LV3)

Physical Layer

ATM

No.7 (LV3)

RRC SignalRRC Signal

RLC

RRC

Node-BUE RNCCN

MSCMSC

RANAP

RANAP

Physical Layer

ATM or No.7 (LV2)

No.7 (LV3)

B-ISUP

No.7 (LV1)

No.7 (LV2)

No.7 (LV3)

B-ISUP No.7(LV4)

Iub SignalingIub Signaling Iu SignalingIu Signaling PSTN SignalingPSTN Signaling

CN

GMSCGMSCPSTN

(No.7 Network)

B-ISUP : Broadband ISDN user part NBAP: Node-B application part

RANAP : Radio access network application part SCCP : Signal connection control part



5.6. Internet Access

Signals are sent in packets for access to internet.

Packet data are sent from UE in IP protocol to internet, and PDCP, RLC and MAC in lowerlayers are used in sending the IP protocol between UE and RNC.

Node B transfers packets to RNC with ATM, and RNC converts them into GTP and transfers

them to SGSN in IP over ATM using UDP (User Datagram Protocol).

In the end, SGSN forwards the packet data to GGSN.

The General Packet Radio Service (GPRS) is a new no voice value added service that allows

information to be sent and received across a mobile telephone network. It supplements

today’s Circuit Switched Data and Short Message Service. GPRS is NOT related to GPS (the

Global Positioning System), a similar acronym that is often used in mobile contexts. GPRS

has several unique features which can be summarized as:

SPEED

Theoretical maximum speeds of up to 171.2 kilobits per second (kbps) are achievable with

GPRS using all eight timeslots at the same time. This is about three times as fast as the data

transmission speeds possible over today fixed telecommunications networks and ten times as

fast as current Circuit Switched Data services on GSM networks.

IMMEDIACY

GPRS facilitates instant connections whereby information can be sent or received

immediately as the need arises. No dial-up modem connection is necessary. This is why GPRS

users are sometimes referred to be as being "always connected". Immediacy is one of the

advantages of GPRS (and SMS) when compared with Circuit Switched Data. High immediacy

is a very important feature for time critical applications such as remote credit card

authorization where it would be unacceptable to keep the customer waiting for even thirty

extra seconds.

Fig. 7.21illustrates an image of the protocol stack for internet access. The data transmitted

by mobiles are received at RNC in Layer 2 PDCP, where they are forwarded to GGSN in

Layer 2 GTP.



Fig. 7.20 Internet Access

Fig. 7.21 Internet Access

Internet Access

Protocol Stack (Layer)

MobileLayer 1 Physical Layer

ATM

Physical Layer

ATM

GTP

Node-BUE RNC CNSGSNSGSN

Physical Layer

ATM

GTP

CNGGSNGGSN

Physical Layer

Layer 2

Internet

Upper Layer (TCP etc.)

IP

PDCP

Node-B

RNC

GGSNGGSNGGSNSGSNSGSNSGSN

CN

Iub Interface Iu Interface Gi Interface

T r a f f i c

C h a

n n e l

Internet Access

System Outline

H : Packet header GTP: GPRS tunneling protocol

IP : Internet protocol

Data H

IP PacketIP PacketData

H

GTP PacketGTP Packet

Data H

UE

(IP Packet)(IP Packet)

Data

H

PDCP PacketPDCP Packet

Data H

PDCPPDCPIP

GTPGTP

Tunneling Tunneling

Internet

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