WCDMA-P&O-C-EN-Basal Theory-1-201006£¨draft£©

7/29/2019 WCDMA-P&O-C-EN-Basal Theory-1-201006draft

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WCDMA Basal Theory


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Contents

1 Overview of WCDMA ..................................................................................................................................1

1.1 Overview ..................................................................................................................................................1

1.2 WCDMA Technical Standards Development Trends ..............................................................................2

1.2.1 3GPP Standard Development Status ........................................................................................2

1.2.2 Analysis on 3GPP standard Version Evolution ........................................................................6

1.2.3 Analysis on Evolution of 3GPP Technologies ..........................................................................7

1.3 IMT2000 Frequency Band Allocation ...................................................................................................11

1.4 Composition of WCDMA System ........................................................................................................12

1.4.1 UE (User Equipment ) ............................................................................................................12

1.4.2 UTRAN (UMTS Terrestrial Radio Access Network ) ...........................................................12

1.4.3 CN (Core Network) ................................................................................................................13

2 WCDMA Technology Basics ........................................................................................................................1

2.1 Concept of WCDMA Realizing Broadband Communication .................................................................1

2.1.1 Basic Concepts of CDMA ........................................................................................................2

2.1.2 Basic Concepts of Spread Spectrum Communication .............................................................3

2.2 Transmission of Electric Waves in Mobile Environment ........................................................................5

2.2.1 Features of Land Mobile Communication Environment .........................................................5

2.2.2 Signal Fading in Radio Path .....................................................................................................6

2.3 Fundamentals of the WCDMA Technology ............................................................................................6

2.3.1 Channel Coding/Decoding .......................................................................................................6

2.3.2 Principles of Interleaving/Deinterleaving ................................................................................7

2.3.3 Spread Spectrum .......................................................................................................................7

2.3.4 Modulation and Demodulation .................................................................................................8

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1 Overview of WCDMA

1.1 Overview

The 3rd Generation Mobile Communication System (3G) is put on agenda when the 2nd

generation (2G) digital mobile communication market is booming. The 2G mobilecommunication system has the following disadvantages: limited frequency spectrum

resources, low frequency spectrum utilization, and weak support for mobile multimediaservices (providing only speech and low-speed data services). Also, thanks to

incompatibility between 2G systems, the 2G mobile communication system has a lowsystem capacity, hardly meeting the demand for high-speed bandwidth services and

impossible for the system to implement global roaming. Therefore, the 3G communication

technology is a natural result in the advancement of the 2G mobile communication.

As the Internet data services become increasingly popular nowadays, the 3G communicationtechnology opens the door to a brand new mobile communication world. It brings more fun

to the people. In addition to clearer voice services, it allows users to conduct multimediacommunications with their personal mobile terminals, for example, Internet browsing,

multimedia database access, real-time stock quotes query, videophone, mobile e-commerce, interactive games, wireless personal audio player, video transmission,knowledge acquisition, and entertainments. What more unique are location related services,which allow users to know about their surroundings at anytime anywhere, for example,block map, locations of hotels and super markets, and weather forecast. The 3G mobilephone is bound to become a good assistant to peoples life and work.

The 3G mobile communication aims at meeting the future demand for mobile user capacityand providing mobile data and multimedia communication services.

Initially, mobile communication technologies were developed separately, as variouscountries and technical organizations continued to develop their own technologies. Thus, the

USA has AMPS, D-AMPS, IS-136, and IS-95, Japan has PHS, PDC, and the EU has GSM. Onone hand, this situation helped to meet the needs of the users at the early stage of mobilecommunication and expand the mobile communication market. On another hand, it createdbarriers between the regions, and made it necessary to unify the mobile communicationsystems globally. Under such a context, ITU launched the standardization of the 3G mobilecommunication system in 1985.

The 3G mobile communication system, IMT-2000, is the general term for the next

generation communication system proposed by ITU in 1985, when it was actually referredto as Future Public Land Mobile Telecommunications System (FPLMTS). In 1996, it wasofficially renamed to IMT-2000. In addition, the 3G mobile communication technologyextends the integrated bandwidth network service as far as it can to the mobileenvironment, transmitting multimedia information including high quality images at rates upto 10 Mbps.

Compared with the existing 2G system, the 3G system has the following characteristics assummarized below:

1. Support for multimedia services, especially Internet services

2. Easy transition and evolution

3. High frequency spectrum utilization


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Currently, the three typical 3G mobile communication technology standards in the world areCDMA2000, WCDMA and TD-SCDMA. CDMA2000 and WCDMA work in the FDD mode, whileTD-SCDMA works in the TDD mode, where the uplink and downlink of the system work indifferent timeslots of the same frequency.

The 3G mobile communication is designed to provide diversified and high-quality multimediaservices. To achieve these purposes, the wireless transmission technology must meet thefollowing requirements:

1. High-speed transmission to support multimedia services

Indoor environment: >2 Mbps

Outdoor walking environment: 384 Mbps

Outdoor vehicle moving: 144 kbps

2. Allocation of transmission rates according to needs

3. Accommodation to asymmetrical needs on the uplink and downlink

In the concept evaluation of the 3G mobile communication specification proposals, theWCDMA technology is adopted as one of the mainstream 3G technologies thanks to itsown technical advantages.

1.2 WCDMA Technical Standards Development Trends

WCDMA was originated by standardization organizations and manufacturers in Europeancountries and Japan. WCDMA inherits the high standardization and openness of GSM, and

its standardization progresses smoothly. WCDMA is the third generation mobilecommunication standard developed by 3GPP, with the GSM MAP as its core and UTRAN(UMTS Terrestrial Radio Access Network) as its wireless interface. Using the chip rate of

3.84 Mbps, it provides data transmission rate up to 14.4 Mbps within 5 MHz bandwidth.

The WCDMA technology has the following characteristics:

Supporting both asynchronous and synchronous BTSs, for easy and flexiblenetworking

Using QPSK modulation mode (the HSDPA services also use the 16QAM modulation

mode)

Using pilot assisted coherent demodulation

Accommodating transmission of multiple rates, and implementing multi-rate andmultimedia services by changing the spread spectrum ratio and using multi-mode

concurrent transmission

Rapid and efficient power control of uplink/downlink greatly reduces multiple accessinterference of the system, but increases the system capacity while reducing the

transmission power.

The core network is evolving based on the GSM/GPRS network, and maintainscompatibility with the GSM/GPRS network.

Supporting soft handover and softer handover, with three handover modes, inter-

sector soft handover, inter-cell soft handover, and inter-carrier hard handover

1.2.1 3GPP Standard Development Status

3GPP standard versions include R99, R4, R5, R6 and R7.


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R99 version was frozen formally in Mar, 2000, and refreshes once every three months.Current commercial version of R99 is based on the version of June, 2001, for in laterversion, the number of CR is decreasing rapidly and there are no larger modifications andnon-compatible upgrade.

R4 version was frozen in Mar, 2001. It passed in Mar, 2002 and is stable currently. R5version was frozen in June, 2002 and is stable currently. Most R5 versions that providerssupport are the version of June, 2004. R6 version was frozen in June, 2005 and may bestable in a year. At present, R7/LTE has started up and its functional features are still ininitial phase.

R99 and R4 versions are put into commercial use maturely. R6 version protocols are indeveloping status.

1.2.1.1 Basic Network Structure Based on R99

Fig. 1.2-1 Basic Network Structure of R99


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The R99 is the first phase version of 3GPP in 3G network standardization. The R99 was

already frozen in June 2001, and subsequent revision is made on the R4. The basicconfiguration structure of the R99 is illustrated in Fig. 1.2-1. To guarantee the investmentinterests of telecom operators, the network structure of the R99 is designed with 2G/3Gcompatibility fully in mind, for smooth evolution to 3G. Therefore, the core network in thebasic network structure remains unchanged. To support 3G services, some NEs are addedwith appropriate interface protocols, and the original interface protocols are also improvedby different degrees.

1.2.1.2 Network Structure Based on UMTS R4

Same as the R99 network, the basic structure of the R4 network consists of the corenetwork and wireless access network, and there are the CS domain and PS domain on the

core network side. The basic NE entities and the interfaces are largely inherited from the

definitions of entities and interfaces of the R99 network. The network entities with the same


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definitions as the R99 network remain unchanged in basic functionality, and the relatedprotocols are also similar.

Compared with the R99, the R4 network structure has tremendous changes in the structure

of the CS domain of the core network, while those of the PS domain of the core network and

of the UTRAN also remain the same.

According to the idea of separation between call control, bearer and bearer control, thenetwork entity (G) MSC of the CS domain of the R99 network evolves to the MGW and (G)

MSCServer in the R4 stage, with R-SGW and T-SGW added. In addition, related interfacesare also changed, with the Mc interface added between the MGW and MSC Sever, the Nc

interface between the MSC Sever and GMSC Sever, and the Nb interface between MGWs,and the Mh interface between the MR-MGW and HLR.

Fig. 1.2-2 Basic Network Structure of the R4


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B S S

B S C

R N S

R N C

C N

N o d e N o d e

I u P S

I u r

I u b

U S I M

M E

M S

C u

U u

M S C s e r

S G S NG s

G G S N

s e r v e r

G nH S S ( H L R )

G r

G cC

D

N c

H

E I R

F G f

G iP S T N

I u C S

V L RB

G p

V L R

G

B T SB T S

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R N C

A b i

S I M

S I M- M E i o r

M S C s e r

B

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c e l l

C S-M G WC S-M G W

-

M G

A u C

N b

T-S G W R-S G

M c

M c

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P S T P S T N

c

M c

M h

A G b

E

1.2.2 Analysis on 3GPP standard Version Evolution

During the evolution from GSM/GPRS to 3GPP R99, brand UTRAN introduced includes suchkey technologies as WCDMA, power control, multipath Rake receiver. In addition, four QoSservice types are put forward and cell peak rate supports up to 2 Mbps. CN basically

develops from GSM/GPRS CN. It reduces the influence on GSM/GPRS CN caused by theintroduction of UTRAN CN furthest. Most representative features of R4 from R99: Separation

of CS domain control layer and transmission layer, convergence of transmission resources inCS and PS domains, and increase of resource transmission efficiency.

UTRAN in R4 version does not have substantive evolution and only performs someoptimizations.

During the evolution from R4 to R5, IP multimedia subsystem is introduced into CN and the


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interface connecting GERAN is added. There is great change in UTRAN: IP transmissiontechnology and HSDPA are introduced, which makes peak rate of the cell up to about 10Mbps, much greater than the peak bandwidth that R4 and R99 versions can support (in thefield, WCDMA supporting HSDPA is called 3.5 G). R5 also supports Iu Flexible, allowing a

RNC to access several MSCs or SGSNs simultaneously, which saves investment on accessnetwork resources for operators.

intercommunication of WLAN and UMTS. UTRAN evolution includes: MBMS, HSUPA,enhanced HSDPA, wave cluster figuration technology to increase coverage capacity, 3GPPRET and MOCN.

In R7 plans. WCDMA will be developing in total IP direction. In addition, intercommunication of UTMS with

other networks (such as, VLAN) and enhanced MBMS will be increased.

1.2.3 Analysis on Evolution of 3GPP Technologies

1.2.3.1 Evolution of CN Technology

Total IP CN

Brand UTRAN is introduced in initial phase of 3GPP R99, to reduce the influence of

UTRAN on CN. Introduction policy of CN is developed from GSM/GPRS CN.

During the evolution from R99 to R4, CN realizes the separation of CS domain controllayer and transmission layer, realizes voice packet and signaling packet, transmits CSand PS domains application in CN based on one IP.

During the evolution from R4 to R5, 3GPP CN introduced IMS based on packet domain.IMS adopts Session Initiation Protocol (SIP) that IETF defines and provides IP servicesthat Qos is sensitive to (such as, VoIP) in packet switching domain, to intercommunicate

fixed IP terminal and 3G mobile terminal.In R6 version, functions of IMS are enhanced greatly, including the intercommunicationof local IP multimedia network and other IP multimedia networks, intercommunication ofIMS and CS, intercommunication of IMS based on IPV4 and IPV6, multi-party conferenceservice, IMS group management and SIP appended to IMS. As a result, wider and moreflexible IP-based multimedia services are provided for operation.

During the evolution from R99 to R7, CN may absolutely abandon circuit switching

domain in the future and develops into a total IP service mobile network.

Network sharing

In 3GPP R99/R4, one RNC can only connect one MSC or SGSN, resulting in lowutilization ratio of resources.

In R5, Iu-Flex is introduced between CN and UTRAN, realizing the UTRAN resourcessharing among several nodes of one operator. It saves the cost on UTRAN and

substantially develops the network sharing technology.

In R6, network sharing function is expanded continuously, which provides the

configuration mode of Multiple Operator Core Network (MOCN). MOCN allows severaloperators to share one radio access network in sharing area. As a result, operators can

save investment on UTRAN.

Amalgamation with other networks

In 3GPP R6, intercommunication and amalgamation of UMTS and WLAN are fulfilled(Phase I), which is strengthened in R7 plans (Phase II). In addition, in R7, defines

feasibility of total IP network operation. Intercommunication and amalgamation of CN


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with other networks is future development trend.

1.2.3.2 Evolution of Radio Access Network Technologies

High-speed broadband access

Compared with GSM/GPSR RAN, R99 introduced new UTRAN. UTRAN is based onWCDMA radio interface technology. Its signal bandwidth is 5 MHz. Its code chip rate is3.84 Mbps. Its cell downlink service bandwidth is about 2 M.

R4 version has no large change in radio access.

In R5 version, HSDPA is introduced. It adopts 16 QAM modulation mode, which greatlyincreases spectrum utilization ratio. Cell downlink peak rate reaches 14 Mbps. In thefield, the system supporting HSDPA is defaulted as 3.5 G system.

In R6 version, HSUPA is introduced, which makes cell uplink peak rate up to 5.7 Mbps.

In R7 version, Multiple Input Multiple Output (MIMO) antenna technology is introduces,

which enables several transmitting and receiving antennas to send and receive signalsin same band. As a result, system capacity and spectrum utilization ratio is increased in

germination. MIMO antenna technology meets the requirements for high speed servicesin future mobile communication system. In Long Term Evolution (LTE) items,Orthogonal Frequency Division Multiplexing (OFDM) is introduced, which makes celldownlink peak rate up to 39 Mbps. It may develop as the core technology base of 3Gadvanced system (such as, Beyond 3G, 3.9G and E3G). With continuous developmentof 3GPP standardization, OFDM will be applied to broadband mobile communication fieldmore widely in the near future.

In the future, MIMO and OFDM technologies will combine. System test results improvethat MIMO-OFDM system which has two transmission antennas and two receivingantennas can provide the data transmission rate from score to a hundred million.

In a word, evolution process of radio access network on access bandwidth is: 2 Mbps(R99) HSDPA DL 14 Mbps (R5) HSDPA DL 14 Mbps/HSUPA UL 5.7 Mbps (R6) -->

MIMO (R7) OFDM (LTE). Its evolution is to introduce all kinds of technologies,increasing spectrum utilization ratio furthest and meeting the requirements for highspeed data transmission.

Mobile management

From R99 version, WCDMA has differences from GSM/GPRS in mobile management,including soft handover, Iur interface, re-positioning, handover and reselection between2/3G. From R4 version, Iur interface has introduced such flows as public measurementand radio link congestion, which makes radio resource management and load control of

Iur interface be organic part of UTRAN. At the same time, amalgamation criteria with

GERAN are under way, including Iur-g, cell change that network aids.

IP transmission

UTRAN in R99/R4 versions adopts TDM and ATM. CN in R4 version successfully

introduces the base of IP transmission technology.

3GPP UTRAN in R5 version also introduces IP transmission technology. IP transmission is

a selective technology of UTRAN and it makes UTRAN transmit based on IP coreswitching network. As a result, flexibility of transmission networking is increased and

construction cost of operators is reduced. IP transmission is also UTRAN transmissiondevelopment trend.

In transmission, R4/R5 versions added transmission bearer modification and

reconfiguration, to further optimize the performance of transmission bearer.


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Antenna technology

During the evolution of 3GPP standards, 3GPP also has evolution in antenna technology

and antenna evolution process is: Two projects of wave cluster figuration (R5) Fixed

wave cluster figuration project and 3GPP electronic modulation antenna (R6) MIMO

(R7).

The evolution is to improve link performance of the system by introducing all kinds ofantenna technologies, increasing system capacity.

In R5 version, radio wave cluster figuration technology is introduced to increase systemlink performance and capacity. Two projects are put forward: fixed wave clusterfiguration and user special wave cluster figuration. In R6 version, user special wavecluster figuration project is deleted and fixed wave cluster figuration project is decided.

In mobile BS network planning and optimization, common measure is to remotelymodulate antennas of BS system. Most operators purchase antennas from third party.In these years, Antenna Interface Standard Group (AISG) has put forward AISGinterface standards. However, since 3GPP does not definite antenna interfaces inR99/R4/R5 phases, it is difficulty for manufacturers to have same antenna interface,antenna type and network optimization. Therefore, in R6 version, 3GPP uniformsinterface of RET and introduces Iuant antenna interfaces. Standardization of RETinterfaces makes remote network optimization possible on condition that several

manufacturers provide antennas.

In R7 version, 3GPP puts forward MIMO, which increases system capacity and spectrumutilization ratio in germinations. Although MIMO is not mature at present, it is a greatbreakthrough of antenna technology in mobile communication field and also a

developing direction of future intelligent antenna technology.

Positioning technology

In R99 version, UE positioning technology based on cell ID is introduced. It is a roughpositioning technology. In R99 version, frames of OTDOA and A-GPS are introduced,

too.

In R4 version, criteria of Iub/Iur interfaces are put forward, which improves OTDOA and

A-GPS positioning technologies.

In R5 version, criteria of SMLC-SRNC interfaces are put forward and they are open tosupport A-GPS positioning technology (not supporting other positioning technologies).

In R4 and R5, lowest performance requirements for A-GPS measurement are not given.

Therefore, in R6 version, positioning precision of A-GPS is defined (positioning range ofa mobile station is 30 to 100 m and response time is 2 to 20 s. In R6 version, SMLC-SRNC interfaces are open to support three positioning technologies (CellID, OTDOA and

A-GPS).

In R7 version, Uplink-Time Difference Of Arrival (U-TDOA) is put forward. It is hoped toprovide solutions that are more flexible and whose positioning precision is higher.

The evolution process of positioning technology is: Cell ID OTDOA AGPS U-TDOA. It is a process from rough positioning technology to the positioning technologywith high precision. All positioning technologies can be supplements to each other during

the application.

1.2.3.3 Evolution of UMTS QoS Technology

With the close combination of radio communication technology and IP technology, mobile

communication network develops from circuit switching network of GSM to packet switching

network of GSM, and to 3G, 3.5G and UMTS that provide high speed real-time data


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services. During the whole evolution of mobile network, QoS technology develops to matureto provide satisfactory services according to features of different services. Analysis on QoSin GSM, GPRS, R99, R4, R5, R6 and R7 tell development of mobile network QoS.

GSM is based on circuit switching mode. It is simple. Connection of circuit can ensure QoS.

GSM defines a series of circuit bearer services, including parameters ofsynchronization/asynchronization, transparent/non-transparent, and limited bit rate set.They are continuously effective during the evolution of mobile network.

GPRS is based on packet switching mode. There is no Connection concept in GPRS, so QoSassurance of GPRS is more complicated than that of GSM. QoS parameters that GPRS

defines are: Delay level, confidence level, largest data flow, PRI, even data flow andretransmission demand. QoS parameters can be transmitted between UE and SGSN/GGSN.

QoS of UMTS is to provide end-to-end assurance of services, which is introduced in R99version, as shown in Fig. 1.2-3. End-to-end QoS covers all NEs, including user terminal,

access network entity and CN entity. Processing of different interface QoS parameters mustbe same. The introduction of QoS layered architecture is a large advancement during the

QoS evolution.

Fig. 1.2-3 QoS Frame of UMTS

TE CN

Gateway

MT UTRAN CN Iu

EDGE

NO DE

TE

End-to-End Service

TE/MT Local

Bearer ServiceUMTS B earer Service

External

Bearer Service

Radio Access B earer ServiceCN Bearer

Service

Radio

Bearer Service

Iu

Bearer Service

Backbone

Bearer Service

UTRA

FDD/TDD

Service

Physical

Bearer Service

UMTS

Operators decide the bearer mode that UMTS CN adopts. Its circuit domain can supportTDM and ATM bearing modes (in R4 and later version, transmission and control in circuitdomain is separated and IP transmission is selective). Its packet domain supports IP bearer.TDM and ATM bearers both provide QoS assurance. IP bearer of CN adopts the QoS

technology that IETF defines, including integrated service/resource preservation(IntServ/RSVP), Multiple Protocol Label Switching (MPLS), Differential Service (DiffServ),

flow project and constraint-based path seek, and so on.

In R99 version, four QoS types are introduced: Conversational, data streaming, interactiveand background. It also defines QoS parameters more than GSM and GPRS. There are newrequirements for transmission delay, retransmission mechanism, jitter and code error rate

of above four types.


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In R4 version, QoS that AAL2 connects on Iub and Iur is optimized, to improve real-timeservices support. In addition, QoS negotiation mechanism of radio access bearer isintroduced to make use of radio resources more effectively and to enhance the constructioncapability of radio access bearer.

In R5 version, intercommunication and combination of UE local bearer service, GPRS bearerservice and outer bearer service are defined. They provide QoS assurance for end-to-endservices in packet domain. In UE and GGSN, IP BS Manager may exist. It usually usesDiffServ and IntServ/RSVP to communicate with outer IP network. IMS, which is QoS policycontrol mechanism based on services, is also introduced in R5 version.

In R6 version, QoS policy control mechanism based on services is evolved as anindependent functional entity, providing services in all packet domains with QoS policycontrol mechanism based on services. This mechanism separates control and execution ofQoS. Network administrator can consider the whole network, without paying attention todetails, such as, technology and equipment. It reflects the intelligent management of QoS.

In R7 version, amalgamation of UTMS and WLAN is put forward. Uniform IP QoS is what

future UMTS QoS technology will develop to.

Evolution process of QoS is: QoS parameters do not transmit in the network (GSM) QoS

parameters transmit between UE and SGSN/GGSN Number of QoS parameters increase

(GPRS) QoS layered architecture, four QoS types, QoS that IETF defines, all NEs that QoS

parameters cover, new change in parameters, the number of parameters increase (R99)

QoS negotiation mechanism of radio access bearer (R4) QoS policy control mechanism

based on services in IMS (R5) QoS policy control mechanism based on services in all

packet domain (R6) Uniform IP QoS in the amalgamation of UMTS and WLAN (R7 andlater version).

1.3 IMT2000 Frequency Band AllocationIn 1992, World Radio-communication Conference (WRC-92) allocated the frequency bandsfor the 3G mobile communication, with a total bandwidth of 230 MHz, as shown in Fig. 1.3-4.

Fig. 1.3-4 Frequency Spectrum Allocation of 3G Mobile Communication


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At WRC92, ITU planned the symmetric frequency spectrum resources of 120MHz (1920MHz~ 1980MHz, 2110MHz ~ 2170MHz) for use by the FDD, and asymmetric frequency

spectrum resources of 35MHz (1900MHz ~ 1920MHz, 2010MHz ~ 2025MHz) for use by theTDD.

At WRC2000, the 800 MHz band (806MHz ~ 960MHz), 1.7GHz band (1710MHz ~1885MHz), and 2.5GHz band (2500MHz ~ 2690MHz) were added for use by the IMT-2000services. These two combined make the future spectrum for 3G reach over 500 MHz,reserving enormous resource space for future applications.

1.4 Composition of WCDMA SystemThe Universal Mobile Telecommunication System (UMTS) is a 3G mobile communicationsystem adopting WCDMA air interface. Therefore, the UMTS is usually called a WCDMAsystem.

In terms of functions, the network units comprise the Radio Access Network (RAN) and Core

Network (CN). The RAN accomplishes all the functions related to radio communication. TheCN handles the exchange and routing of all the calls and data connections within the UMTSwith external networks. The RAN, CN, and the User Equipment (UE) together constitute thewhole UMTS.

1.4.1 UE (User Equipment )

The UE is an equipment which can be vehicle installed or hand portable. Through the Uuinterface, the UE exchanges data with network equipment and provides various CS domainand PS domain services, including common voice services, broadband voice services, mobilemultimedia services, and Internet applications (such as E-mail, WWW browse, and FTP).

1.4.2 UTRAN (UMTS Terrestrial Radio Access Network )

The UMTS Terrestrial Radio Access Network (UTRAN) comprises Node B and Radio networkController (RNC).

1) Node B1.

As the base station (wireless transceiver) in the WCDMA system, the Node B is


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composed of the wireless transceiver and baseband processing part. Connected with theRNC through standard Iub interface, Node B processes the Un interface physical layerprotocols. It provides the functions of spectrum spreading/despreading,modulation/demodulation, channel coding/decoding, and mutual conversion between

baseband signals and radio signaling.2) RNC

The RNC manages various interfaces, establishes and releases connections, performs

handoff and macro diversity/combination, and manages and controls radio resources. Itconnects with the MSC and SGSN through lu interface. The protocol between UE and

UTRAN is terminated here.

The RNC that controls Node B is called Controlling RNC (CRNC). The CRNC performs load

control and congestion control of the cells it serves, and implements admission controland code word allocation for the wireless connections to be established.

If the connection between a mobile subscriber and the UTRAN uses many RNSresources, the related RNC has two independent logical functions:

Serving RNC (SRNC). The SRNC terminates the transmission of subscriber data and theIu connection of RANAP signaling to/from the CN. It also terminates the radio resourcecontrolling signaling (that is the signaling protocol between UE and UTRAN). In addition,the SRNC performs L2 processing of the data sent to/from the radio interface andimplements some basic operations related to radio resources management.

Drift RNC (DRNC) All the other RNCs except the SRNC are DRNCs. They controls the cellsused by the UEs.

1.4.3 CN (Core Network)

The CN is in charge of the connections with other networks as well as the management and

communication with UEs. The CN can be divided into CS domain and PS domain from theaspect of logic.

The CS domain equipment refers to the entities that provide circuit connection or relatedsignaling connection for subscriber services. The specific entities in the CS domain include:

1. Mobile switching center (MSC)

2. Gateway mobile switching center (GMSC)

3. Visitor location register (VLR)

4. Interworking function (IWF).

The PS domain provides packet data services to subscribers. The specific entities in the

PS domain include:

5. Serving GPRS support node (SGSN)

6. Gateway GPRS support node (GGSN)

Other equipment such as the home location register (HLR) or HSS, authentication center(AuC), and equipment identity register (EIR) are shared by the CS domain and PSdomain.

The major functional entities are as follows:

1) MSC/VLR

As the functional node in the CS domain of the WCDMA core network, the MSC/VLR

connects with the UTRAN through Iu CS interface, with external networks (PSTN, ISDN,


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and other PLMNs) through PSTN/ISDN interface, with the HLR/AUC through C/Dinterface, with the MSC/VLR, GMSC or SMC through E interface, with the SCP throughCAP interface, and with the SGSN through Gs interface.

The MSC/VLR accomplishes call connection, mobility management, authentication, and

encryption in the CS domain.

2) GMSC

As the gateway node between the CS domain of WCDMA network and externalnetworks, the GMSC is an optional entity. It connects with the external networks (PSTN,ISDN, and other PLMNs) through PSTN/ISDN interface, with the HLR through Cinterface, and with the SCP through CAP interface.

The GMSC accomplishes the incoming and outgoing routing of the Visited MSC (VMSC).

3) SGSN

As the functional node in the PS domain of WCDMA core network, the SGSN connectswith the UTRAN through Iu_PS interface, with GGSN through Gn/Gp interface, with theHLR/AUC through Gr interface, with the MSC/VLR through Gs interface, with the SCPthrough CAP interface, with the SMC through Gd interface, with the CG through Gainterface, and with the SGSN through Gn/Gp interface.

The SGSN accomplishes the routing forward, mobility management, sessionmanagement, authentication, and encryption in the PS domain.

4) GGSN

The GGSN connects with the SGSN through Gn interface and with the external datanetworks (Internet /Intranet) through Gi interface.

The GGSN provides routes to the data packets between the WCDMA network andexternal data networks, and encapsulates these data packets. The major function of the

GGSN is to provide the interface to the external IP packet-based network, thus the UEscan access the gateway of the external packet-based network. To the external networks,the GGSN seems like the IP router that can be used to address all the mobilesubscribers in the WCDMA network. It exchanges routing information with externalnetworks.

5) HLR

The HLR connects with the VMSC/VLR or GMSC through C interface, with the SGSN

through Gr interface, and with the GGSN through Gc interface. The HLR storessubscriber subscription information, supports new services, and provides enhancedauthentication.


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2 WCDMA Technology Basics

2.1 Concept of WCDMA Realizing Broadband Communication

WCDMA (Wideband CDMA) is CDMA radio communication mode cased on direct spread-spectrum technology. WCDMA has an obvious advantage over GSM and IS-95 insubscriber capacity and radio transmission performance, for it adopts a series of keytechnologies.

WCDMA bears following two meanings literally:

1. WCDMA adopts CDMA communication technology1.CDMA technology is the most advanced communication technology in the world atpresent. It takes advantage of different codes to divide different channel and thendistinguish different subscriber.

2. WCDMA adopts wider spectrum

Narrowband power signals are sent out after being spread as broadband signals(spread-spectrum) with WCDMA technology.Broadband signals have stronger anti-interference ability than narrowband signals. Wider bandwidth realizes RAKE receiving

at subscriber end and increases communication quality.

Fig. 2.1-5 shows WCDMA communication. Bandwidth of original signals increases andpower density decreases after spread-spectrum. Signals meet with noise during thetransmission. Power density of the noise decreases after the dispreading, for spectrumdispreading is the same as spectrum spreading. However, power density of original signalsis much larger than that of noise (that is, signal-to-noise ratio is high) and it is easy to

resume.

Fig. 2.1-5 WCDMA Communication Principle


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F

Power

Density

F

Power

Density

F

Power

Density

F

Power

Density

(1) Original Signal(2) Signal after spread

spectrum

(3)Meeting noise during

signal transmission

(4) Signal and noise after spectrum

dispreading

Signal Noise

WCDMA adopts such advanced technologies as soft handover, diversity and power control

to enlarge system capacity and increase communication quality greatly.

2.1.1 Basic Concepts of CDMA

Mobile communication systems can be classified in multiple ways. For example, there areanalog and digital by the nature of the signals; FM, PM, and AM by the modulation mode;and FDMA, TDMA and CDMA by the multiple access mode. CDMA (Code Division MultipleAccess) is a new while mature wireless technology developed from the spread spectrum

communication technology, a branch of the digital technology.

Currently, the GSM mobile telephone networks of China Unicom and China Mobile are builtwith the combination of FDMA and TDMA. GSM has tremendous advantages over theanalog mobile telephone system. However, its spectrum efficiency is only three times of

the analog system. With a limited capacity, it has difficulty in offering voice qualityequivalent to wired telephone. TDMA terminals support an access rate of only 9.6 kbps.

The TDMA system does not support soft handover, so calls may easily be dropped,affecting the service quality. Therefore, TDMA is not the best technology for modern

cellular mobile communication. On the other hand, CDMA fully meets the requirements ofmodern mobile communication networks for large capacity, high quality, and integratedservices, so it is well received by increasingly more operators and users.

CDMA emerges from the needs for wireless communications of higher quality. In the

CDMA communication system, the signals used by different users for informationtransmission are distinguished not by frequencies or timeslots, but by different code

sequences. CDMA allocates one pseudo random binary sequence for each signal forfrequency spreading, and different signals are allocated with different pseudo randombinary sequences. In the receiver, correlators are used to separate the signals. The


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correlator of each user only receives the specified binary sequences and compresses their

frequency spectrums, while ignoring all the other signals.

The code division multiple access concept of CDMA can be illustrated with a party of manypersons. At the party, many users talk at the same time in a room, and everyconversation in the room is in a language you do not understand. From your perspective,

all these conversations sound like noise. If you know these codes, that is, relevantlanguages, you can ignore the conversations you do not want to hear, and focus on only

these you are interested in. The CDMA system filters the traffic in a similar way. However,even if you understand all the languages used, you do not necessarily hear clearly all theconversations you are interested in. In this case, you can tell the speakers to speaklouder, and/or ask others to lower their voices. This is similar to the power control in theCDMA system. In the frequency domain or time domain, multiple CDMA signals overlap.The receiver can sort out the signals that use the preset code pattern from multiple CDMA

signals by using correlators. Other signals using different code patterns are notdemodulated, since their code patterns are different from those generated locally at the

receiver.

One of the basic technologies of CDMA is spectrum spreading. CDMA is a multiple accesstechnology featuring high confidentiality. It was first developed in the Second World Warto prevent interference from the enemies. CDMA found wide application in anti-

interference military communications during the war. After 1960s, it had been used inmilitary satellite communication. Later, it was developed by Qualcomm into a commercial

mobile communication technology.

After the first CDMA system was put into operation for commercial purpose in 1995, thetechnical advantages of the CDMA in theory were tested in practice, so it has seen rapidapplication in North America, South America and Asia. In many countries and regions in

the world, including China, Hong Kong, South Korea, Japan, and USA, CDMA is the major

mobile communication technology used. CDMA is superior to TDMA in system capacity,anti-interference, communication quality, and confidentiality, so IMT-2000 (3G) launchedby ITU and subsequent standards all employ CDMA.

2.1.2 Basic Concepts of Spread Spectrum Communication

The basic characteristic of spread spectrum communication is that it uses a bandwidth forinformation transmission much wider than that of the information itself. In other words,

the data for transmission with certain signal bandwidth is modulated with high-speedpseudo random codes having a bandwidth wider than the signal bandwidth. Thus, the

bandwidth of the original data signals is spread, before the signals are transmittedfollowing carrier modulation. The receiving end uses exactly the same pseudo random

codes to process the received bandwidth signals, converting the broadband signals intothe original narrowband signals, that is, despreading, thus achieving informationcommunication.

In addition, spread spectrum communication also has the following characteristics:

1. It is a d1. igital transmission mode.

2. Bandwidth spreading is implemented by modulating the transmitted information with afunction (spread spectrum function) irrelevant to the transmitted information.

3. At the receiving end, the same spread spectrum function is used to demodulate the

spread spectrum signals, restoring the transmitted information.

C.E. Shannon found the channel capacity formula in his research in information theory,

as below:


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C = W Log2 (1+S/N)

Where:

C Information transmission rate

S Available signal power

W Bandwidth of the line

N Noise power

As can be seen from the formula:

To increase C, you can either increase W or increase S/N. In other words, when C is

constant, W and S/N are interchangeable, where the increase of W reduces the

requirement for S/N. When the bandwidth increases to a certain level, the S/N is allowed

to further decrease, making it possible for the useful signal power to decrease to a level

close to the noise power or even inundated in the noise. Spread spectrum communication

uses the bandwidth transmission technology to obtain the benefit in S/N, which is the

basic idea and theoretical basis of spread spectrum communication.

Spread spectrum communication has many outstanding performances insuperable by

narrowband communication, enabling it to find wide application rapidly in various

public and private communication networks. Its advantages are outlined as below:

1. Powerful anti-interference and low bit error rate

The spread spectrum communication system spreads the signal spectrum at thetransmitting end and restores the original information at the receiving end, producingspread gains, thus greatly increasing the anti-jamming margin. Depending on thespread spectrum gains, signals can be extracted from noise even when the S/N isnegative. In the current commercial communication system, spread spectrumcommunication is the only communication mode that can work in the negative S/N

environment.

2. Easy same frequency use for higher radio spectrum utilization

Radio spectrum is very valuable. Although all waves from long wave and micro wavehave been developed and used, the need of the society is not satisfied. For this

reason, frequency spectrum management authorities were set up all over the world.Users can only use the frequencies granted, and divide them into channels to avoidmutual interference.

As spread spectrum communication uses the correlation reception technology, the

signal transmission power is extremely low (


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with a related technology. Also, the same code sequence waveform from multiple

paths can be added for reinforcement, to achieve effective anti multipath interference.

4. Spread spectrum communication is a form of digital communication, particularlysuitable for synchronous transmission of digital voice and data. Spread spectrumcommunication offers the encryption function for good confidentiality, making it easy

to launch various communication services.

Using multiple new technologies including code division multiple access, and voicecompression, spread spectrum communication is more suitable for transmission ofcomputer network and digitized voices and images.

5. Spread spectrum communication involves mostly digital circuitry. Its equipment ishighly integrated, easy to install and maintain, compact, and reliable and easy tomount/expand, and has a long MTBF.

2.2 Transmission of Electric Waves in Mobile Environment

The target of mobile communication system is to gradually realize personal communication

using the always existent radio channel as transmission media. However, the radiochannel has poor transmission features. Firstly, there is serious and complicated fading,including path fading, shadow fading, and multipath fading. Secondly, the radiotransmission path may be direct or obstructed by mountains or buildings. It is difficult toanalyze the unknown and unpredictable elements in radio channels. Even the relativemoving speed may greatly affect the fading of signal level.

Although the features of electromagnetic waves change a lot during transmission, themajor changes fall into perpendicular incidence, reflection, diffraction (inflection), andscattering. In cities, there is no direct path between transmitters and receivers. The highbuildings and large mansions cause serious diffraction loss. Reflected by objects by manytimes, the electromagnetic waves reach the receiver through different paths. Theinteraction of these electromagnetic waves cause multipath fading at specific place. In a

word, the strength of electromagnetic waves decreases with the extension of the distancebetween the transmitter and receiver.

2.2.1 Features of Land Mobile Communication Environment

1. Low Antenna of MS

Because the transmission path is always affected by topography and man-made

environment, and the MS moves in various topographical environment and buildings, it

makes the signal received by the MS become the increment of a large number ofscattered and reflected signals.

2. Mobility of MS

The MS is always moving. Even the MS is not moving, the surroundings alwayschange, for example, people and vehicles move, and wind blows leaves. The mobilitymakes the transmission path between the base station and MS always change. Inaddition, the moving direction and speed of the MS will cause the change of signal

level.

3. Random Change of Signal Level

Varying with the time and locations, the signal level can be described by the

probability distribution in random process only.


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4. Wave Guide Effect in Metropolitan Environment

The wave guide effect caused by the high buildings on both sides of the street make

the signals received in the direction parallel to the street enhanced and the signalsreceived in the vertical direction weakened. There is about 10 dB difference betweenthe two signals. This effect is attenuated 8 km away from the base stations.

5. Loud Man-Made Noise

The man-made noise includes noise of vehicles and electric power lines, as well as

industrial noise.

6. Strong interference

The common interferences include co-channel interference, adjacent-channelinterference, intermodulation interference, and near-far interference.

2.2.2 Signal Fading in Radio PathAs the MS moves further from the base station, the signal received becomes weaker andweaker. The reason is that path loss occurs to the signal. The factors causing the path loss

include carrier frequency, transmission speed, and the topography and physiognomywhere the signal is transmitted.

Shadow effect: The semi-dead zone in the coverage area caused by the obstruct of highbuildings and other objects.

Near-far effect: Because the mobile subscribers move at free will, the distance betweenthe subscriber and the base station changes. If the MSs have the same transmit power,the signal strength at the base station is different. If the MS is nearer to the base station,the signal received by the base station is stronger. The non-linearity of the communication

system will be worsened, making the stronger signal stronger, the weaker signal weaker,and the stronger signal suppress the weaker signal.

Doppler effect: The shift in frequency which results from the move of the signal receivedat high rate. The degree of shift is in direct ratio with the velocity of the mobile subscriber.

2.3 Fundamentals of the WCDMA Technology

2.3.1 Channel Coding/Decoding

A radio channel is an adverse transmission channel. When digital signals transmitted over

a radio channel, bit errors may occur in the transmission data flow due to various reasons,causing image jumps and disconnection at the receive end. The step of channel coding canbe used to process the data flow appropriately, so that the system can have errorcorrection capability and anti-interference capability to certain extent, thus greatlyavoiding bit errors in the code flow. Therefore, channel coding aims at increasing data

transmission efficiency by reducing bit error rate.

Ultimately, channel coding intends to increase the reliability of the channel, but it mayreduce the transmission of useful information data. Channel coding works by insertingsome code elements, usually referred to as overhead, into the source data code flow, forerror detection and correction at the receiving end. This is like the transport of glasses. Toensure that no glasses are broken during this process, we usually use foams or sponge to

package them. However, such packaging reduces the total number of glasses. Similarly,

over a channel with fixed bandwidth, the total transmission code rate is fixed. As channel


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coding increases data amount, the useful information code rate is reduced. This is the

cost. The number of useful bits divided by the total number of bits derives the codingefficiency, which varies slightly from one coding mode to another.

The coding/decoding technology and interleaving technology can work together toincrease the bit error performance. Compared with the case without coding, the traditional

convolution code can increase the bit error rate by two orders of magnitude, to 10-3 ~ 10-4,and the Turbo code can further increase the bit error rate to 10 -6. Because the Turbo code

has a coding performance close to the limit of Shannon theorem, it is adopted as the datacoding/decoding technology for 3G. The convolution code is mainly used for voice andsignaling of low data rates.

2.3.2 Principles of Interleaving/Deinterleaving

Interleaving/deinterleaving is an important step of the combined channel error correction

system. The actual errors in the channel are usually burst errors or both burst errors andrandom errors. If burst errors are first discretized into random errors, which are thencorrected, the systems anti-interference performance can be improved. The interleaverworks to discretize long burst errors or multiple burst errors into random errors, that is,discretizing the errors.

The interleaving technology rearranges the coded signals by following certain rules. After

deinterleaving, burst errors are dispersed over time, making them similar to randomerrors that occur separately.

2.3.3 Spread Spectrum

Spread Spectrum is an information transmission mode. It modulates information signals

with spreading code at sending end and enables spectrum width of information signalsmuch wider than bandwidth for information transmission. It dispreads at receiving endwith same spreading code, to resume data of transmitted information.

Fig. 2.3-6 shows basic operations of spectrum spread/dispread. Supposing subscriber datarate is R, subscriber data is 101101, and according to the rule that 1 is mapped as -1, 0 is

mapped as +1, map subscriber data as -1+1-1-1+1-1 and time it with spreading code.Spreading code is 01101001 in this example. Time each subscriber data bit to this code

series including 8 code chips. Concluded data rate after spread is 8 R and is random,like spreading code. Its spread spectrum factors are 8.

Broadband signals after spread spectrum are transmitted to receiving end via radiochannels. Time code sequence with same spread spectrum code (dispreading code) when

dispreading at receiving end to resume original subscriber data.Spreading signal speed by 8 times factor may result in bandwidth spreading of subscriberdata signals (therefore, CDMA system is often called spread spectrum system).Dispreading resumes signal rate to original rate.

Fig. 2.3-6 Spectrum Spreading/Dispreading in DS-CDMA


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Subscriber data

= -1+1-1-1+1-1

Spread spectrum =

+1-1-1+1-1+1+1-1

Spreading signal =

Subscriber data *

Spread spectrum

Dispreading data

= Subscriber data

* Spread

spectrum

1

1

1

1

1

1

1

1

1

1

Spectrum dispreading

Spectrum spreading

Distributing different spread spectrum to different subscriber can distinguish different

subscriber, as shown in above sector.Supposing that there are three subscribers and that signals they send are b1, b2 and b3,

spread their signals with spreading code of c1, c2 and c3 and final sending signal isy=b1c1 + b2c2 + b3c3. Supposing that there is no interference in signal transmission, the

receiving end:

Gets signals after dispread with c1

z1 = y * c1 = c1 * (b1c1 + b2c2 + b3c3) = b1 + (b2c2c1 + b3c3c1)


z2 = y * c2 = c2 * (b1c1 + b2c2 + b3c3) = b2 + (b1c1c2 + b3c3c2)


z3 = y * c3 = c3 * (b1c1+b2c2+b3c3) = b3 + (b1c1c3 + b2c2c3)

All parts in the brackets in above three formulas are interference of other subscriber

signals to this signal. This interference can be absolutely avoided if using orthogonalizedcodes. Orthogonalized code is the code that is 1 after timing itself and is 0 after timingother codes. So:

z1 = y * c1 = c1 * (b1c1 + b2c2 + b3c3) = b1 + (b2c2c1 + b3c3c1) = b1 + 0 + 0 = b1



2.3.4 Modulation and Demodulation

Modulation is the process to use one signal (know as modulation signal) to control anothersignal of carrier (known as carrier signal), so that a characteristic parameter of the later

changes with the former. At the receiving end, the process to restore the original signalfrom the modulated signal is called demodulation.

During signal modulation, a high-frequency sine signal is often used as the carrier signal.One sine signal involves three parameters: amplitude, frequency and phase. Modulation ofeach of these three parameters is respectively called amplitude modulation, frequencymodulation, and phase modulation.

In the WCDMA system, the modulation is Quaternary Phase Shift Keying (QPSK). If HighSpeed Downlink Package Access (HSDPA) is used, the downlink modulation mode can alsobe 16QAM.


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Modulating rate of WCDMA uplinks/downlinks are both 3.84 Mcps and modulate complex-

valued code chip sequence generated by spread spectrum in QPSK mode.

Fig. 2.3-7 shows uplink modulation and Fig. 2.3-8 shows downlink modulation.

Fig. 2.3-7 Uplink Modulation

S

Im{S}

Re{S}

cos(t)

Complex-valuedchip sequencefrom spreadingoperations

-sin(t)

Splitreal &imag.parts

Pulse-shaping

Pulse-shaping

Fig. 2.3-8 Downlink Modulation

T

Im{T}

Re{T}

cos( t)

Complex-valuedchip sequencefrom summingoperations

-sin( t)

Splitreal &imag.parts

Pulse-shaping

Pulse-shaping

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