WCDMA RAN Fundamental

WCDMA RAN Fundamental

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Page1Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

Objectives

l Upon completion of this course, you will be able to:

p Describe the development of 3G

p Outline the advantage of CDMA principle

p Characterize code sequence

p Outline the fundamentals of RAN

p Describe feature of wireless propagation




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Contents

1. 3G Overview

2. CDMA Principle

3. WCDMA Network Architecture and protocol structure

4. WCDMA Wireless Fundamental




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Contents

1. 3G Overview

2. CDMA Principle






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Different Service, Different Technology

AMPS

TACS

NMT

Others

1G 1980sAnalog

GSMGSM

CDMA CDMA IS-95IS-95

TDMATDMAIS-136IS-136

PDCPDC

2G 1990sDigital

Technologies drive

3G IMT-2000

UMTSUMTSWCDMAWCDMA

cdmacdma20002000

Demands drive

TD-SCDMATD-SCDMA

3G provides compositive services for both operators and subscribers

l The first generation is the analog cellular mobile communication network in the time period from the middle of 1970s to the middle of 1980s. The most important breakthrough in this period is the concept of cellular networks put forward by the Bell Labs in the 1970s, as compared to the former mobile communication systems. The cellular network system is based on cells to implement frequency reuse and thus greatly enhances the system capacity.

l The typical examples of the first generation mobile communication systems are the AMPS system and the later enhanced TACS of USA, the NMT and the others. The AMPS (Advanced Mobile Phone System) uses the 800 MHz band of the analog cellular transmission system and it is widely applied in North America, South America and some Circum-Pacific countries. The TACS (Total Access Communication System) uses the 900 MHz band. It is widely applied in Britain, Japan and some Asian countries.

l The main feature of the first generation mobile communication systems is that they use the frequency reuse technology, adopt analog modulation for voice signals and provide an analog subscriber channel every other 30 kHz/25 kHz.

l However, their defects are also obvious:

p Low utilization of the frequency spectrum

p Limited types of services

p No high-speed data services

p Poor confidentiality and high vulnerability to interception and number embezzlement

p High equipment cost




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l To solve these fundamental technical defects of the analog systems, the digital mobile

communication technologies emerged and the second generation mobile

communication systems represented by GSM and IS-95 came into being in the middle

of 1980s. The typical examples of the second generation cellular mobile

communication systems are the DAMPS of USA, the IS-95 and the European GSM

system.

l The GSM (Global System for Mobile Communications) is originated from Europe.

Designed as the TDMA standard for mobile digital cellular communications, it supports

the 64 kbps data rate and can interconnect with the ISDN. It uses the 900 MHz band

while the DCS1800 system uses the 1800 MHz band. The GSM system uses the FDD

and TDMA modes and each carrier supports eight channels with the signal bandwidth

of 200 kHz.

l The DAMPS (Digital Advanced Mobile Phone System) is also called the IS-54 (North

America Digital Cellular System). Using the 800 MHz bandwidth, it is the earlier of the

two North America digital cellular standards and specifies the use of the TDMA mode.

l The IS-95 standard is another digital cellular standard of North America. Using the 800

MHz or 1900 MHz band, it specifies the use of the CDMA mode and has already

become the first choice among the technologies of American PCS (Personal

Communication System) networks.

l Since the 2G mobile communication systems focus on the transmission of voice and

low-speed data services, the 2.5G mobile communication systems emerged in 1996 to

address the medium-rate data transmission needs. These systems include GPRS and IS-

95B.

l The CDMA system has a very large capacity that is equivalent to ten or even twenty

times that of the analog systems. But the narrowband CDMA technologies come into

maturity at a time later than the GSM technologies, their application far lags behind

the GSM ones and currently they have only found large-scale commercial applications

in North America, Korea and China. The major services of mobile communications are

currently still voice services and low-speed data services.

l With the development of networks, data and multimedia communications have also

witnessed rapid development; therefore, the target of the 3G mobile communication

is to implement broadband multimedia communication.

l The 3G mobile communication systems are a kind of communication system that can

provide multiple kinds of high quality multimedia services and implement global

seamless coverage and global roaming. They are compatible with the fixed networks

and can implement any kind of communication at any time and any place with

portable terminals.




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3G Evolution

l Proposal of 3G

p IMT-2000: the general name of third generation mobile

communication system

p The third generation mobile communication was first proposed in

1985and was renamed as IMT-2000 in the year of 1996

n Commercialization: around the year of 2000

n Work band : around 2000MHz

n The highest service rate :up to 2000Kbps

l Put forward in 1985 by the ITU (International Telecommunication Union), the 3G mobile communication system was called the FPLMTS (Future Public Land Mobile

Telecommunication System) and was later renamed as IMT-2000 (International Mobile Telecommunication-2000). The major systems include WCDMA, cdma2000 and UWC-

136. On November 5, 1999, the 18th conference of ITU-R TG8/1 passed the Recommended Specification of Radio Interfaces of IMT-2000 and the TD-SCDMA

technologies put forward by China were incorporated into the IMT-2000 CDMA TDD part of the technical specification. This showed that the work of the TG8/1 in

formulating the technical specifications of radio interfaces in 3G mobile communication systems had basically come into an end and the development and

application of the 3G mobile communication systems would enter a new and essential phase.

l The 3GPP is an organization that develops specifications for a 3G system based on the

UTRA radio interface and on the enhanced GSM core network.

l The 3GPP2 initiative is the other major 3G standardization organization. It promotes

the CDMA2000 system, which is also based on a form of WCDMA technology. In the world of IMT-2000, this proposal is known as IMT-MC. The major difference between

the 3GPP and the 3GPP2 approaches into the air interface specification development is that 3GPP has specified a completely new air interface without any constraints from

the past, whereas 3GPP2 has specified a system that is backward compatible with IS-95 systems.




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3G Spectrum Allocation

l ITU has allocated 230 MHz frequency for the 3G mobile communication system IMT-

2000: 1885 ~ 2025MHz in the uplink and 2110~ 2200 MHz in the downlink. Of them,

the frequency range of 1980 MHz ~ 2010 MHz (uplink) and that of 2170 MHz ~ 2200

MHz (downlink) are used for mobile satellite services. As the uplink and the downlink

bands are asymmetrical, the use of dual-frequency FDD mode or the single-frequency

TDD mode may be considered. This plan was passed in WRC92 and new additional

bands were approved on the basis of the WRC-92 in the WRC2000 conference in the

year 2000: 806 MHz ~ 960 MHz, 1710 MHz ~ 1885 MHz and 2500 MHz ~ 2690 MHz.




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Bands WCDMA Used

l Main bands

p 1920 ~ 1980MHz / 2110 ~ 2170MHz

l Supplementary bands: different country maybe different

p 1850 ~ 1910 MHz / 1930 MHz ~ 1990 MHz (USA)

p 1710 ~ 1785MHz / 1805 ~ 1880MHz (Japan)

p 890 ~ 915MHz / 935 ~ 960MHz (Australia)

p . . .

l Frequency channel numbercentral frequency5, for main band:

p UL frequency channel number 96129888p DL frequency channel number : 1056210838

l The WCDMA system uses the following frequency spectrum (bands other than those

specified by 3GPP may also be used): Uplink 1920 MHz ~ 1980 MHz and downlink

2110 MHz ~ 2170 MHz. Each carrier frequency has the 5M band and the duplex

spacing is 190 MHz. In America, the used frequency spectrum is 1850 MHz ~ 1910

MHz in the uplink and 1930 MHz ~ 1990 MHz in the downlink and the duplex spacing

is 80 MHz.




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3G Application Service

Time Delay

Error Ratio

background

conversational

streaming

interactive

l Compatible with abundant services and applications of 2G, 3G system has an open

integrated service platform to provide a wide prospect for various 3G services.

l Features of 3G Services

l 3G services are inherited from 2G services. In a new architecture, new service

capabilities are generated, and more service types are available. Service characteristics

vary greatly, so each service features differently. Generally, there are several features

as follows:

p Compatible backward with all the services provided by GSM.

p The real-time services (conversational) such as voice service

generally have the QoS requirement.

p The concept of multimedia service (streaming, interactive,

background) is introduced.




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The Core technology of 3G: CDMA

CDMA

WCDMAWCDMACN: based on MAP and GPRS

RTT: WCDMA

TD-SCDMACN: based on MAP and GPRS

RTT: TD-SCDMA

cdma2000CN: based on ANSI 41 and MIP

RTT: cdma2000

l Formulated by the European standardization organization 3GPP, the core network

evolves on the basis of GSM/GPRS and can thus be compatible with the existing

GSM/GPRS networks. It can be based on the TDM, ATM and IP technologies to evolve

towards the all-IP network architecture. Based on the ATM technology, the UTRAN

uniformly processes voice and packet services and evolves towards the IP network

architecture.

l The cdma2000 system is a 3G standard put forward on the basis of the IS-95 standard.

Its standardization work is currently undertaken by 3GPP2. Circuit Switched (CS)

domain is adapted from the 2G IS95 CDMA network, Packet Switched (PS) domain is

A packet network based on the Mobile IP technology. Radio Access Network (RAN) is

based on the ATM switch platform, it provides abundant adaptation layer interfaces.

l The TD-SCDMA standard is put forward by the Chinese Wireless Telecommunication

Standard (CWTS) Group and now it has been merged into the specifications related to

the WCDMA-TDD of 3GPP. The core network evolves on the basis of GSM/GPRS. The

air interface adopts the TD-SCDMA mode.




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Contents

1. 3G Overview

2. CDMA Principle






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Multiple Access and Duplex Technology

l Multiple Access Technology

p Frequency division multiple access (FDMA)

p Time division multiple access (TDMA)

p Code division multiple access (CDMA)

l In mobile communication systems, GSM adopts TDMA; WCDMA, cdma2000 and TD-

SCDMA adopt CDMA.




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Multiple Access Technology

Freque

ncy

Time

Power

FDMA

Freque

ncyTime

Power

TDMA

Power

Time

CDMA

Frequency

l Frequency Division Multiple Access means dividing the whole available spectrum into

many single radio channels (transmit/receive carrier pair). Each channel can transmit

one-way voice or control information. Analog cellular system is a typical example of

FDMA structure.

l Time Division Multiple Access means that the wireless carrier of one bandwidth is

divided into multiple time division channels in terms of time (or called timeslot). Each

user occupies a timeslot and receives/transmits signals within this specified timeslot.

Therefore, it is called time division multiple access. This multiple access mode is

adopted in both digital cellular system and GSM.

l CDMA is a multiple access mode implemented by Spreading Modulation. Unlike FDMA

and TDMA, both of which separate the user information in terms of time and

frequency, CDMA can transmit the information of multiple users on a channel at the

same time. The key is that every information before transmission should be modulated

by different Spreading Code to broadband signal, then all the signals should be mixed

and send. The mixed signal would be demodulated by different Spreading Code at the

different receiver. Because all the Spreading Code is orthogonal, only the information

that was be demodulated by same Spreading Code can be reverted in mixed signal.




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Multiple Access and Duplex Technology

l Duplex Technology

p Frequency division duplex (FDD)

p Time division duplex (TDD)

l In third generation mobile communication systems, WCDMA and cdma2000 adopt

frequency division duplex (FDD), TD-SCDMA adopts time division duplex (TDD).




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Duplex Technology

Time

Frequency

Power

TDD

USER 2

USER 1

DLUL

DLDL

UL

FDD

Time

Frequency

Power

UL DL

USER 2

USER 1




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Contents

1. 3G Overview

2. CDMA Principle






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WCDMA Network Architecture

RNS

RNC

RNS

RNC

Core Network

Node B Node B Node B Node B

Iu-CS Iu-PS

Iur

Iub IubIub Iub

CN

UTRAN

UEUu

CS PS

Iu-CSIu-PS

CSPS

l WCDMA including the RAN (Radio Access Network) and the CN (Core Network). The

RAN is used to process all the radio-related functions, while the CN is used to process

all voice calls and data connections within the UMTS system, and implements the

function of external network switching and routing.

l Logically, the CN is divided into the CS (Circuit Switched) Domain and the PS (Packet

Switched) Domain. UTRAN, CN and UE (User Equipment) together constitute the

whole UMTS system

l A RNS is composed of one RNC and one or several Node Bs. The Iu interface is used

between RNC and CN while the Iub interface is adopted between RNC and Node B.

Within UTRAN, RNCs connect with one another through the Iur interface. The Iur

interface can connect RNCs via the direct physical connections among them or

connect them through the transport network. RNC is used to allocate and control the

radio resources of the connected or related Node B. However, Node B serves to

convert the data flows between the Iub interface and the Uu interface, and at the

same time, it also participates in part of radio resource management.




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WCDMA Network Version Evolution

3GPP Rel993GPP Rel4

3GPP Rel5

2000 2001 2002

GSM/GPRS CN

WCDMA RTT

IMS

HSDPA 3GPP Rel6

MBMS

HSUPA

2005

CS domain change to NGN

WCDMA RTT

l The overall structure of the WCDMA network is defined in 3GPP TS 23.002. Now,

there are the following three versions: R99, R4, R5.

l 3GPP began to formulate 3G specifications at the end of 1998 and beginning of 1999.

As scheduled, the R99 version would be completed at the end of 1999, but in fact it

was not completed until March, 2000. To guarantee the investment benefits of

operators, the CS domain of R99 version do not fundamentally change., so as to

support the smooth transition of GSM/GPRS/3G.

l After R99, the version was no longer named by the year. At the same time, the

functions of R2000 are implemented by the following two phases: R4 and R5. In the

R4 network, MSC as the CS domain of the CN is divided into the MSC Server and the

MGW, at the same time, a SGW is added, and HLR can be replaced by HSS (not

explicitly specified in the specification).

l In the R5 network, the end-to-end VOIP is supported and the core network adopts

plentiful new function entities, which have thus changed the original call procedures.

With IMS (IP Multimedia Subsystem), the network can use HSS instead of HLR. In the

R5 network, HSDPA (High Speed Downlink Packet Access) is also supported, it can

support high speed data service.

l In the R6 network, the HSUPA is supported which can provide UL service rate up to

5.76Mbps. And MBMS (MultiMedia Broadcast Multicast Service) is also supported.




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WCDMA Network Version Evolution

l Features of R6

p MBMS is introduced

p HSUPA is introduced to achieve the service rate up to 5.76Mbps

l Features of R7

p HSPA+ is introduced, which adopts higher order modulation and MIMO

p Max DL rate: 28Mbps, Max UL rate:11Mbps

l Features of R8

p WCDMA LTE (Long term evolution) is introduced

p OFDMA is adopted instead of CDMA

p Max DL rate: 100Mbps, Max UL rate: 50Mbps (with 20MHz bandwidth)




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Uu Interface protocol structure

L3

cont

rol

cont

rol

cont

rol

cont

rol

C-plane signaling U-plane information

PHY

L2/MAC

L1

RLC L2/RLC

MAC

RLCRLCRLC

NAS (non-access stratum)

UuS boundary

L2/BMC

control

PDCPPDCP L2/PDCP

RRC

RLCRLCRLC

RLC

BMC

l The layer 1 supports all functions required for the transmission of bit streams

on the physical medium. It is also in charge of measurements function

consisting in indicating to higher layers, for example, Frame Error Rate (FER),

Signal to Interference Ratio (SIR), interference power and transmit power.

l The layer 2 protocol is responsible for providing functions such as mapping,

ciphering, retransmission and segmentation. It is made of four sublayers: MAC

(Medium Access Control), RLC (Radio Link Control), PDCP (Packet Data

Convergence Protocol) and BMC (Broadcast/Multicast Control).

l The layer 3 is split into 2 parts: the access stratum and the non access stratum.

The access stratum part is made of RRC (Radio Resource Control) entity and

duplication avoidance entity. The non access stratum part is made of CC, MM

parts.

l Not shown on the figure are connections between RRC and all the other

protocol layers (RLC, MAC, PDCP, BMC and L1), which provide local inter-layer

control services.

l The protocol layers are located in the UE and the peer entities are in the NodeB

or the RNC.




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General Protocol Mode for UTRAN Terrestrial Interfacel The structure is based on the principle that the layers and planes are

logically independent of each other.

Application Protocol

Data Stream(s)

ALCAP(s)

Transport Network

Layer

Physical Layer

Signaling Bearer(s)

Control Plane User Plane

Transport NetworkUser Plane

Transport Network Control Plane

Radio Network

Layer

Signaling Bearer(s)

Data Bearer(s)


l Protocol structures in UTRAN terrestrial interfaces are designed according to the same general protocol model. This model is shown in above slide. The structure is based on the principle that the layers and planes are logically independent of each other and, if needed, parts of the protocol structure may be changed in the future while other parts remain intact.

l Horizontal Layers

p The protocol structure consists of two main layers, the Radio Network Layer (RNL) and the Transport Network Layer (TNL). All UTRAN-related issues are visible only in the Radio Network Layer, and the Transport Network Layer represents standard transport technology that is selected to be used for UTRAN but without any UTRAN-specific changes.

l Vertical Planes

p Control Plane

p The Control Plane is used for all UMTS-specific control signaling. It includes the Application Protocol (i.e. RANAP in Iu, RNSAP in Iur and NBAP in Iub), and the Signaling Bearer for transporting the Application Protocol messages. The Application Protocol is used, among otherthings, for setting up bearers to the UE (i.e. the Radio Access Bearer in Iu and subsequently the Radio Link in Iur and Iub). In the three plane structure the bearer parameters in the Application Protocol are not directly tied to the User Plane technology, but rather are general bearer parameters. The Signaling Bearer for the Application Protocol may or may not be of the same type as the Signaling Bearer for the ALCAP. It is always set up by O&M actions.




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p User Plane

p All information sent and received by the user, such as the coded voice in a voice call or the packets in an Internet connection, are transported via the User Plane. The User Plane includes the Data Stream(s), and the Data Bearer (s) for the Data Stream(s). Each Data Stream is characterized by one or more frame protocols specified for that interface.

p Transport Network Control Plane

p The Transport Network Control Plane is used for all control signaling within the Transport Layer. It does not include any Radio Network Layer information. It includes the ALCAP protocol that is needed to set up the transport bearers (Data Bearer) for the User Plane. It also includes the Signaling Bearer needed for the ALCAP. The Transport Network Control Plane is a plane that acts between the Control Plane and the User Plane. The introduction of the Transport Network Control Plane makes itpossible for the Application Protocol in the Radio Network Control Plane to be completely independent of the technology selected for the Data Bearer in the User Plane.

l About AAl2 and AAL5

p Above the ATM layer we usually find an ATM adaptation layer (AAL). Its function is to process the data from higher layers for ATM transmission.

p This means segmenting the data into 48-byte chunks and reassembling the original data frames on the receiving side. There are five different AALs (0, 1, 2, 3/4, and 5). AAL0 means that no adaptation is needed.The other adaptation layers have different properties based on three parameters:

n Real-time requirements;

n Constant or variable bit rate;

n Connection-oriented or connectionless data transfer.

p The usage of ATM is promoted by the ATM Forum. The Iu interface uses two AALs: AAL2 and AAL5.

p AAL2 is designed for the transmission of connection oriented, real-time data streams with variable bit rates.

p AAL5 is designed for the transmission of connectionless data streams with variable bit rates.




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Iu-CS Interface (based on ATM)

ALCAPALCAP

Control Plane

Transport NetworkControl Plane

User planeRadioNetworkLayer


TransportNetworkLayer

A B

RANAP

AAL2 PATH

ATM

Physical Layer

SAAL NNI

SCCPMTP3-B

Iu UP

SAAL NNI

MTP3-B


l Protocol Structure for Iu CS

p The Iu CS overall protocol structure is depicted in above slide. The three planes in the Iu interface share a common ATM (Asynchronous Transfer Mode) transport which is used for all planes. The physical layer is the interface to the physical medium: optical fiber, radio link or copper cable. The physical layer implementation can be selected from a variety of standard off-the-shelf transmission technologies, such as SONET, STM1, or E1.

l Iu CS Control Plane Protocol Stack

p The Control Plane protocol stack consists of RANAP, on top of Broadband (BB) SS7 (Signaling System #7) protocols. The applicable layers are the Signaling Connection Control Part (SCCP), the Message Transfer Part (MTP3-b) and SAAL-NNI (Signaling ATM Adaptation Layer for Network to Network Interfaces).

l Iu CS Transport Network Control Plane Protocol Stack

p The Transport Network Control Plane protocol stack consists of the Signaling Protocol for setting up AAL2 connections (Q.2630.1 andadaptation layer Q.2150.1), on top of BB SS7 protocols. The applicable BB SS7 are those described above without the SCCP layer.

l Iu CS User Plane Protocol Stack

p A dedicated AAL2 connection is reserved for each individual CS service.




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Iu-CS Interface (based on IP)

Control Plane User planeRadioNetworkLayer



RANAP

IP

Physical Layer

IP

SCTP

Iu UP


DATA LINK DATA LINK

M3UASCCP RTP/RTCP

UDP

l SCTP is streaming control transmission protocol. It is a reliable transport protocol operating on top of IP.

l M3UA is MTP3 user adaption layer based on IP.

l RTP is real-time transmission protocol. It provides CS data IP-based transmission




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Iu-PS Interface (based on ATM)


Transport NetworkUser PlaneTransport

NetworkLayer


C

RANAP

ATM

SAAL NNI

SCCP

MTP3-B

Iu UP

AAL Type 5IP

UDPGTP-U

Physical Layer

l Protocol Structure for Iu PS

p The Iu PS protocol structure is represented in above slide. Again, a common ATM transport is applied for both User and Control Plane.Also the physical layer is as specified for Iu CS.

l Iu PS Control Plane Protocol Stack

p The Control Plane protocol stack consists of RANAP, on top of Broadband (BB) SS7 (Signaling System #7) protocols. The applicable layers are the Signaling Connection Control Part (SCCP), the Message Transfer Part (MTP3-b) and SAAL-NNI (Signaling ATM Adaptation Layer for Network to Network Interfaces).

l Iu PS Transport Network Control Plane Protocol Stack

p The Transport Network Control Plane is not applied to Iu PS. Thesetting up of the GTP tunnel requires only an identifier for the tunnel, and the IP addresses for both directions, and these are already included in the RANAP RAB Assignment messages.

l Iu PS User Plane Protocol Stack

p In the Iu PS User Plane, multiple packet data flows are multiplexed on one or several AAL5 PVCs. The GTP-U (User Plane part of the GPRS Tunneling Protocol) is the multiplexing layer that provides identities for individual packet data flow. Each flow uses UDP connectionless transport and IP addressing.




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Iu-PS Interface (based on IP)




RANAP

IP

Physical Layer

IP

SCTP

Iu UP


DATA LINK DATA LINK

M3UASCCP

GTP-U

UDP

l SCTP is streaming control transmission protocol. It is a reliable transport protocol operating on top of IP.

l M3UA is MTP3 user adaption layer based on IP.




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Iub Interface (based on ATM)

ALCAPALCAP

Control Plane






NBAP

AAL2 PATH

ATM

Physical Layer

SAAL UNI

Iub FP

SAAL UNI

NCP CCP

l The Iub interface is the terrestrial interface between NodeB and RNC. The Radio

Network Layer defines procedures related to the operation of the NodeB. The

Transport Network Layer defines procedures for establishing physical

connections between the NodeB and the RNC.

l The Iub application protocol, NodeB application part ( NBAP ) initiates the

establishment of a signaling connection over Iub . It is divided into two

essential components, CCP and NCP.

l NCP is used for signaling that initiates a UE context for a dedicated UE or

signals that is not related to specific UE. Example of NBAP-C procedure are cell

configuration , handling of common channels and radio link setup

l CCP is used for signaling relating to a specific UE context.

l SAAL is an ATM Adaptation Layer that supports communication between

signaling entities over an ATM link.

l The user plane Iub Frame Protocol ( FP ), defined the structure of the frames

and the basic in band control procedure for every type of transport channel.

There are DCH-FP, RACH-FP, FACH-FP, HS-DSCH FP and PCH FP.




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Iub Interface (based on IP)





NBAP

IP

DATA LINK

Physical Layer

IP

Iub FP

NCP CCP

DATA LINK

SCTP UDP




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Iur Interface (based on ATM)

ALCAPALCAP

Control Plane




A B

RNSAP

AAL2 PATH

ATM

Physical Layer

SAAL NNI

SCCPMTP3-B

Iur Data Stream

SAAL NNI

MTP3-B



l Iur interface connects two RNCs. The protocol stack for the Iur is shown in

above slide.

l The RNSAP protocol is the signaling protocol defined for the Iur interface.




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Iur Interface (based on IP)




RNSAP

IP

Physical Layer

IP

SCTP

Iu UP


DATA LINK DATA LINK

M3UASCCP

UDP




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Contents

1. 3G Overview

2. CDMA Principle






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Processing Procedure of WCDMA System

SourceCoding

Channel Coding& Interleaving

Spreading Modulation

SourceDecoding

Channel Decoding& Deinterleaving

Despreading Demodulation

Transmission

Reception

chipmodulated

signalbitsymbol

ServiceSignal

Radio Channel

ServiceSignal

Receiver

l Source coding can increase the transmitting efficiency.

l Channel coding can make the transmission more reliable.

l Spreading can increase the capability of overcoming interference.

l Through the modulation, the signals will transfer to radio signals from digital signals.

l Bit, Symbol, Chip

p Bit : data after source coding

p Symbol: data after channel coding and interleaving

p Chip: data after spreading




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WCDMA Source Coding

l AMR (Adaptive Multi-Rate) Speech

p A integrated speech codec with 8

source rates

p The AMR bit rates can be controlled by

the RAN depending on the system load

and quality of the speech connections

l Video Phone Service

p H.324 is used for VP Service in CS

domain

p Includes: video codec, speech codec,

data protocols, multiplexing and etc.

5.15AMR_5.15

4.75AMR_4.75

5.9AMR_5.90

6.7 (PDC EFR)AMR_6.70

7.4 (TDMA EFR)AMR_7.40

7.95AMR_7.95

10.2AMR_10.20

12.2 (GSM EFR)AMR_12.20

Bit Rate (kbps)CODEC

l AMR is compatible with current mobile communication system (GSM, IS-95, PDC and

so on), thus, it will make multi-mode terminal design easier.

l The AMR codec offers the possibility to adapt the coding scheme to the radio channel

conditions. The most robust codec mode is selected in bad propagation conditions.

The codec mode providing the highest source rate is selected in good propagation

conditions.

l During an AMR communication, the receiver measures the radio link quality and must

return to the transmitter either the quality measurements or the actual codec mode

the transmitter should use during the next frame. That exchange has to be done as

fast as possible in order to better follow the evolution of the channels quality.




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Transmitter

SourceCoding



SourceDecoding



Transmission

Reception

chipmodulated

signalbitsymbol

ServiceSignal

Radio Channel

ServiceSignal

Receiver




l Scrambling can make transmission in security.


l Bit, Symbol, Chip







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WCDMA Block Coding - CRC

l Block coding is used to detect if there are any uncorrected

errors left after error correction.

l The cyclic redundancy check (CRC) is a common method of

block coding.

l Adding the CRC bits is done before the channel encoding and

they are checked after the channel decoding.

l During the transmission, there are many interferences and fading. To guarantee

reliable transmission, system should overcome these influence through the channel

coding which includes block coding, channel coding and interleaving.

l Block coding: The encoder adds some redundant bits to the block of bits and the

decoder uses them to determine whether an error has occurred during the

transmission. This is used to calculate Block Error Ratio (BLER) used in the outer loop

power control.

l The CRC (Cyclic Redundancy Check) is used for error checking of the transport blocks

at the receiving end. The CRC length that can be inserted has four different values: 0,

8, 12, 16 and 24 bits. The more bits the CRC contains, the lower is the probability of

an undetected error in the transport block in the receiver.

l Note that certain types of block codes can also be used for error correction, although

these are not used in WCDMA.




N-36


WCDMA Channel Coding

l Effect

p Enhance the correlation among symbols so as to recover the signal when

interference occurs

p Provides better error correction at receiver, but brings increment of the delay

l Types

p No Coding

p Convolutional Coding (1/2, 1/3)

p Turbo Coding (1/3)

Code Block of N Bits

No Coding

1/2 Convolutional Coding

1/3 Convolutional Coding

1/3 Turbo Coding

Uncoded N bits

Coded 2N+16 bits

Coded 3N+24 bits

Coded 3N+12 bits

l UTRAN employs two FEC schemes: convolutional codes and turbo codes. The idea is to add redundancy to the transmitted bit stream, sO that occasional bit errors can be

corrected in the receiving entity.

l The first is convolution that is used for anti-interference. Through the technology,

many redundant bits will be inserted in original information. When error code is caused by interference, the redundant bits can be used to recover the original

information. Convolutional codes are typically used when the timing constraints are tight. The coded data must contain enough redundant information to make it possible

to correct some of the detected errors without asking for repeats.

l Turbo codes are found to be very efficient because they can perform close to the

theoretical limit set by the Shannons Law. Their efficiency is best with high data rate services, but poor on low rate services. At higher bit rates, turbo coding is more

efficient than convolutional coding.

l In WCDMA network, both Convolution code and Turbo code are used. Convolution code applies to voice service while Turbo code applies to high rate data service.

l Note that both block codes and channel codes are used in the UTRAN. The idea behind this arrangement is that the channel decoder (either a convolutional or turbo

decoder) tries to correct as many errors as possible, and then the block decoder (CRC check) offers its judgment on whether the resulting information is good enough to be

used in the higher layers.




N-37


WCDMA Interleaving

l Effect

p Interleaving is used to reduce the probability of consecutive bits error

p Longer interleaving periods have better data protection with more delay

11101........................0000100

0 0 1 0 0 0 0 . . . 1 0 1 1 1

11101........................0000100

0 0 0 1 0 1 0 0 1 0 1 1 Inter-column permutation

Output bits

Input bits

Interleaving periods: 20, 40, or 80 ms

l Channel coding works well against random errors, but it is quite vulnerable to bursts

of errors, which are typical in mobile radio systems. The especially fast moving UE in

CDMA systems can cause consecutive errors if the power control is not fast enough to

manage the interference. Most coding schemes perform better on random data errors

than on blocks of errors. This problem can be eased with interleaving, which spreads

the erroneous bits over a longer period of time. By interleaving, no two adjacent bits

are transmitted near to each other, and the data errors are randomized.

l The longer the interleaving period, the better the protection provided by the time

diversity. However, longer interleaving increases transmission delays and a balance

must be found between the error resistance capabilities and the delay introduced.




N-38



SourceCoding



SourceDecoding



Transmission

Reception

chipmodulated

signalbitsymbol

ServiceSignal

Radio Channel

ServiceSignal

Receiver






l Bit, Symbol, Chip







N-39


Correlation

l Correlation measures similarity between any two arbitrary signals.

l Identical and Orthogonal signals:

Correlation = 0Orthogonal signals

-1 1 -1 1

-1 1 -1 1

1 1 1 1

+1

-1+1

-1

+1

-1

+1

-1

Correlation = 1Identical signals

-1 1 -1 1

1 1 1 1

-1 1 -1 1

C1

C2+1

+1

C1

C2

l Correlation is used to measure similarity of any two arbitrary signals. It is computed by

multiplying the two signals and then summing (integrating) the result over a defined

time windows. The two signals of figure (a) are identical and therefore their

correlation is 1 or 100 percent. In figure (b) , however, the two signals are

uncorrelated, and therefore knowing one of them does not provide any information

on the other.




N-40


Orthogonal Code Usage - Coding

UE1: 1 1

UE2: 1 1

C1 : 1 1 1 1 1 1 11

C2 : 1 1 1 1 1 1 1 1

UE1c1 1 1 1 1 1 1 11

UE2c2 1 1 1 1 1 1 1 1

UE1c1 UE2c2 2 0 2 0 2 0 2 0

UE1: 1 1

UE2: 1 1

C1 : 1 1 1 1 1 1 11

C2 : 1 1 1 1 1 1 1 1

UE1c1 1 1 1 1 1 1 11

UE2c2 1 1 1 1 1 1 1 1

UE1c1 UE2c2 2 0 2 0 2 0 2 0

l By spreading, each symbol is multiplied with all the chips in the orthogonal sequence

assigned to the user. The resulting sequence is processed and is then transmitted over

the physical channel along with other spread symbols. In this figure, 4-digit codes are

used. The product of the user symbols and the spreading code is a sequence of digits

that must be transmitted at 4 times the rate of the original encoded binary signal.




N-41


Orthogonal Code Usage - Decoding

UE1C1 UE2C2: 2 0 2 0 2 0 2 0

UE1 Dispreading by c1: 1 1 1 1 1 1 11

Dispreading result: 2 0 2 0 2 0 2 0

Integral judgment: 4 (means1) 4 (means1)

UE2 Dispreading by c2: 1 1 1 1 1 1 1 1



UE1C1 UE2C2: 2 0 2 0 2 0 2 0

UE1 Dispreading by c1: 1 1 1 1 1 1 11



UE2 Dispreading by c2: 1 1 1 1 1 1 1 1



l The receiver dispreads the chips by using the same code used in the transmitter.

Notice that under no-noise conditions, the symbols or digits are completely recovered

without any error. In reality, the channel is not noise-free, but CDMA system employ

Forward Error Correction techniques to combat the effects of noise and enhance the

performance of the system.

l When the wrong code is used for dispreading, the resulting correlation yields an

average of zero. This is a clear demonstration of the advantage of the orthogonal

property of the codes. Whether the wrong code is mistakenly used by the target user

or other users attempting to decode the received signal, the resulting correlation is

always zero because of the orthogonal property of codes.




N-42


Spectrum Analysis of Spreading & Dispreading

Spreading code

Spreading code

Signal Combination

Narrowband signalf

P(f)

Broadband signal

P(f)

f

Noise & Other Signal

P(f)

f

Noise+Broadband signal

P(f)

f

Recovered signal P(f)

f

l Traditional radio communication systems transmit data using the minimum bandwidth

required to carry it as a narrowband signal. CDMA system mix their input data with a

fast spreading sequence and transmit a wideband signal. The spreading sequence is

independently regenerated at the receiver and mixed with the incoming wideband

signal to recover the original data. The dispreading gives substantial gain proportional

to the bandwidth of the spread-spectrum signal. The gain can be used to increase

system performance and range, or allow multiple coded users, or both. A digital bit

stream sent over a radio link requires a definite bandwidth to be successfully

transmitted and received.




N-43


Spectrum Analysis of Spreading & Dispreading

Max allowed interference

Eb/No Requirement

Power

Max interference caused by UE and others

Processing Gain

Ebit

Interference from other UE Echip

Eb / No = Ec / No PG




N-44


Process Gain

l Process Gain

p Process gain differs for each service.

p If the service bit rate is greater, the process gain is smaller, UE

needs more power for this service, then the coverage of this

service will be smaller, vice versa.

)rate bitrate chiplog(10Gain ocessPr =

l For common services, the bit rate of voice call is 12.2kbps, the bit rate of video phone

is 64kbps, and the highest packet service bit rate is 384kbps(R99). After the spreading,

the chip rate of different service all become 3.84Mcps.




N-45


Spreading Technology

l Spreading consists of 2 steps:

p Channelization operation, which transforms data symbols into chips

p Scrambling operation is applied to the spreading signal

scramblingchannelization

Data symbol

Chips after spreading

l Spreading means increasing the bandwidth of the signal beyond the bandwidth

normally required to accommodate the information. The spreading process in UTRAN

consists of two separate operations: channelization and scrambling.

l The first operation is the channelization operation, which transforms every data

symbol into a number of chips, thus increasing the bandwidth of the signal. The

number of chips per data symbol is called the Spreading Factor (SF). Channelization

codes are orthogonal codes, meaning that in ideal environment they do not interfere

each other.

l The second operation is the scrambling operation. Scrambling is used on top of

spreading, so it does not change the signal bandwidth but only makes the signals

from different sources separable from each other. As the chip rate is already achieved

in channelization by the channelization codes, the chip rate is not affected by the

scrambling.




N-46


WCDMA Channelization Code

l OVSF Code (Orthogonal Variable Spreading Factor) is used as

channelization code

SF = 8SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1, -1)

Cch,4,0 = (1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

Cch,8,0 = (1,1,1,1,1,1,1,1)

Cch,8,1 = (1,1,1,1,-1,-1,-1,-1)

Cch,8,2 = (1,1,-1,-1,1,1,-1,-1)

Cch,8,3 = (1,1,-1,-1,-1,-1,1,1)

Cch,8,4 = (1,-1,1,-1,1,-1,1,-1)

Cch,8,5 = (1,-1,1,-1,-1,1,-1,1)

Cch,8,6 = (1,-1,-1,1,1,-1,-1,1)

Cch,8,7 = (1,-1,-1,1,-1,1,1,-1)

l Orthogonal codes are easily generated by starting with a seed of 1, repeating the 1

horizontally and vertically, and then complementing the -1 diagonally. This process is

to be continued with the newly generated block until the desired codes with the

proper length are generated. Sequences created in this way are referred as Walsh

code.

l Channelization uses OVSF code, for keeping the orthogonality of different subscriber

physical channels. OVSF can be defined as the code tree illustrated in the following

diagram.

l Channelization code is defined as Cch SF, k,, where, SF is the spreading factor of the

code, and k is the sequence of code, 0kSF-1. Each level definition length of code tree is SF channelization code, and the left most value of each spreading code

character is corresponding to the chip which is transmitted earliest.




N-47


WCDMA Channelization Code

l SF = chip rate / symbol rate

p High data rates low SF code

p Low data rates high SF code

16Data 128 kbps DL8Data 128 kbps UL




128Speech 12.2 DL64Speech 12.2 UL

SFRadio bearerSFRadio bearer

l The channelization codes are Orthogonal Variable Spreading Factor (OVSF) codes. They are used to preserve orthogonality between different physical channels. They also increase the clock rate to 3.84 Mcps. The OVSF codes are defined using a code tree.

l In the code tree, the channelization codes are individually described by Cch,SF,k, where SF is the Spreading Factor of the code and k the code number, 0 k SF-1.

l A channelization sequence modulates one users bit. Because the chip rate is constant, the different lengths of codes enable to have different user data rates. Low SFs are reserved for high rate services while high SFs are for low rate services.

l The length of an OVSF code is an even number of chips and the number of codes (for one SF) is equal to the number of chips and to the SF value.

l The generated codes within the same layer constitute a set of orthogonal codes. Furthermore, any two codes of different layers are orthogonal except when one of the two codes is a mother code of the other. For example C4,3 is not orthogonal with C1,0and C2,1, but is orthogonal with C2,0.

l SF in uplink is from 4 to 256.

l SF in downlink is from 4 to 512.




N-48


Purpose of Channelization Code

l Channelization code is used to distinguish different physical

channels of one transmitter

p For downlink, channelization code ( OVSF code ) is used to

separate different physical channels of one cell

p For uplink, channelization code ( OVSF code ) is used to separate

different physical channels of one UE

l For voice service (AMR), downlink SF is 128, it means there are 128 voice services

maximum can be supported in one WCDMA carrier;

l For Video Phone (64k packet data) service, downlink SF is 32, it means there are 32

voice services maximum can be supported in one WCDMA carrier.




N-49


Purpose of Scrambling Code

l Scrambling code is used to distinguish different transmitters

p For downlink, scrambling code is used to separate different cells in

one carrier

p For uplink, scrambling code is used to separate different UEs in

one carrier

l In addition to spreading, part of the process in the transmitter is the scrambling

operation. This is needed to separate terminals or base stations from each other.




N-50


Scrambling Code

l Scrambling code: GOLD sequence.

l There are 224 long uplink scrambling codes which are used for

scrambling of the uplink signals. Uplink scrambling codes are assigned

by RNC.

l For downlink, 512 primary scrambling codes are used.

l Different scrambling codes will be planned to different cells in downlink.

l Different scrambling codes will be allocated to different UEs in uplink.

l The scrambling code is always applied to one 10 ms frame.

l In UMTS, Gold codes are chosen for their very low peak cross-correlation.




N-51


Primary Scrambling Code Group

Primary scrambling codes for downlink physical channels

Group 0

Primary scrambling code 0

Primary scrambling code

8*63

Primary scrambling code

8*63 +7512 primary scrambling

codes

Group 1

Group 63



64 primary scrambling code

groupsEach group consists of 8 primary scrambling codes

l There are totally 512 primary scrambling codes defined by 3GPP. They are further

divided into 64 primary scrambling code groups. There are 8 primary scrambling codes

in every group. Each cell is allocated with only one primary scrambling code.




N-52


Code Multiplexing

l Downlink Transmission on a Cell Level

Scrambling code

Channelization code 1



User 1 signal

User 2 signal

User 3 signal

NodeB




N-53


Code Multiplexing

l Uplink Transmission on a Cell Level

NodeB

Scrambling code 3

User 3 signalChannelization code

Scrambling code 2

User 2 signal

Channelization code

Scrambling code 1

User 1 signal

Channelization code




N-54



SourceCoding



SourceDecoding



Transmission

Reception

chipmodulated

signalbitsymbol

ServiceSignal

Radio Channel

ServiceSignal

Receiver






l Bit, Symbol, Chip







N-55


Modulation Overview

1 00 1

time

Basic steady radio wave:

carrier = A.cos(2pFt+f)

Amplitude Shift Keying:

A.cos(2pFt+f)

Frequency Shift Keying:

A.cos(2pFt+f)

Phase Shift Keying:A.cos(2pFt+f)

Data to be transmitted:Digital Input

l A data-modulation scheme defines how the data bits are mixed with the carrier signal,

which is always a sine wave. There are three basic ways to modulate a carrier signal in

a digital sense: amplitude shift keying (ASK), frequency shift keying (FSK), and phase

shift keying (PSK).

l In ASK the amplitude of the carrier signal is modified by the digital signal.

l In FSK the frequency of the carrier signal is modified by the digital signal.

l The PSK family is the most widely used modulation scheme in modern cellular systems.

There are many variants in this family, and only a few of them are mentioned here.




N-56


Modulation Overview

l Digital Modulation - BPSK

1

t

1 10

1

t-1

NRZ coding

fo

BPSKModulated

BPSK signal

Carrier

Information signal

f=0 f=p f=0

1 102 3 4 9875 6

1 102 3 4 9875 6

Digital Input

High FrequencyCarrier

BPSK Waveform

l In binary phase shift keying (BPSK) modulation, each data bit is transformed into a

separate data symbol. The mapping rule is 1 > + 1 and 0 > 1. There are only two possible phase shifts in BPSK, 0 and radians.

l NRZ means none return zero.




N-57


Modulation Overview

l Digital Modulation - QPSK

-1 -1

1 102 3 4 9875 6

1 102 3 4 9875 6

NRZ Input

I di-Bit Stream

Q di-Bit Stream

IComponent

QComponent

QPSK Waveform

1

1

-1

1

-1

1

1

-1

-1

-1

1 1 -1 1 -1 1 1 -1

l The quadrature phase shift keying (QPSK) modulation has four phases: 0, /2, , and 3/2 radians. Two data bits are transformed into one complex data symbol; A symbol is any change (keying) of the carrier.




N-58


Modulation Overview

NRZ coding

90o

NRZ coding

QPSK

Q(t)

I(t)

fo

A

A Acos(wot)

Acos(wot + p/2)

f

1 1 p/41 -1 7p/4-1 1 3p/4-1 -1 5p/4

)cos(2: fw +oAQPSK




N-59


Demodulation

l QPSK Constellation Diagram

1 102 3 4 9875 6

QPSK Waveform

1,1

-1,-1

-1,1

1,-1

1 -11 -1 1 -1-11-1 1

-1,1

NRZ Output




N-60


WCDMA Modulation

l Different modulation methods corresponding to different

transmitting abilities in air interface

HSDPA: QPSK or 16QAMR99/R4: QPSK

l The UTRAN air interface uses QPSK modulation in the downlink, although HSDPA may

also employ 16 Quadrature Amplitude Modulation (16QAM). 16QAM requires good

radio conditions to work well. As seen, with 16QAM also the amplitude of the signal

matters.

l As explained, in QPSK one symbol carries two data bits; in 16QAM each symbol

includes four bits. Thus, a QPSK system with a chip rate of 3.84Mcps could

theoretically transfer 2 3.84 = 7.68 Mbps, and a 16QAM system could transfer 4 3.84 Mbps = 15.36 Mbps. In 3GPP also the usage of 64QAM with HSDPA has been

studied.




N-61



SourceCoding

ChannelCoding


SourceDecoding

ChannelDecoding


Transmission

Reception

chipmodulated

signalbitsymbol

ServiceSignal

Radio Channel

ServiceSignal

Transmitter

Receiver






l Bit, Symbol, Chip







N-62


Wireless Propagation

ReceivedSignal

TransmittedSignal

Transmission Loss:Path Loss + Multi-path Fading

Time

Amplitude

l A mobile communication channel is a multi-path fading channel and any transmitted

signal reaches a receive end by means of multiple transmission paths, such as direct

transmission, reflection, scatter, etc.




N-63


Propagation of Radio SignalSignal at Transmitter

Signal at Receiver

-40

-35

-30

-25

-20

-15

-10

-5

dB

0

0

dBm

-20

-15

-10

-5

5

10

15

20

Fading




N-64


Fading Categories

l Fading Categories

p Slow Fading

p Fast Fading

l Furthermore, with the moving of a mobile station, the signal amplitude, delay and

phase on various transmission paths vary with time and place. Therefore, the levels of

received signals are fluctuating and unstable and these multi-path signals, if overlaid,

will lead to fast fading. Fast fading conforms to Rayleigh distribution. The mid-value

field strength of fast fading has relatively gentle change and is called slow fading.

Slow fading conforms to lognormal distribution.




N-65


Diversity Technique

l Diversity technique is used to obtain uncorrelated signals for

combining

p Reduce the effects of fading

n Fast fading caused by multi-path

n Slow fading caused by shadowing

p Improve the reliability of communication

p Increase the coverage and capacity

l Diversity technology means that after receiving two or more input signals with

mutually uncorrelated fading at the same time, the system demodulates these signals

and adds them up. Thus, the system can receive more useful signals and overcome

fading.




N-66


Diversity

l Time diversity

p Channel coding, Block interleaving

l Frequency diversity

p The user signal is distributed on the whole bandwidth frequency

spectrum

l Space diversity

l Polarization diversity

l Diversity technology is an effective way to overcome overlaid fading. Because it can be

selected in terms of frequency, time and space, diversity technology includes

frequency diversity, time diversity and space diversity.

l Time diversity: Channel coding

l Frequency diversity: WCDMA is a kind of frequency diversity. The signal energy is

distributed on the whole bandwidth.

l Space diversity: using two antennas




N-67


Principle of RAKE Receiver

Receive set

Correlator 1

Correlator 2

Correlator 3

Searcher correlator Calculate the time delay and signal strength

CombinerThe combined

signal

tt

s(t) s(t)

RAKE receiver help to overcome on the multi-path fading and enhance the receive performance of the system

l The RAKE receiver is a technique which uses several baseband correlators to

individually process multipath signal components. The outputs from the different

correlators are combined to achieve improved reliability and performance.

l When WCDMA system is designed for cellular system, the inherent wide-bandwidth

signals with their orthogonal Walsh functions were natural for implementing a RAKE

receiver. In WCDMA system, the bandwidth is wider than the coherence bandwidth of

the cellular. Thus, when the multi-path components are resolved in the receiver, the

signals from different paths are uncorrelated with each other. The receiver can then

combine them using some combining schemes. So with RAKE receiver WCDMA

system can use the multi-path characteristics of the channel to get signal with better

quality.




N-68


Summary

l In this course, we have discussed basic concepts of WCDMA:

p Spreading / Despreading principle

p UTRAN Voice Coding

p UTRAN Channel Coding

p UTRAN Spreading Code

p UTRAN Scrambling Code

p UTRAN Modulation

p UTRAN Transmission/Receiving




N-69

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WCDMA RAN Fundamental

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