1.Need for Umts

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UnderstandingUMTS

The Need for UMTS


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UnderstandingUMTS

The Need for UMTS

1 MOBILE NETWORKS TODAY1.1 Mobile “Generations” 1

1.2 Mobile Network Basics 3

1.3 The 2nd Generation Legacy 5

1.4 Radio Access Schemes 71.5 Focus in on GSM Network Elements 9

2 MODERN MOBILE SERVICE NEEDS2.1 2G: A Changing Market 11

2.2 General Trends in Telecommunications 13

2.3 Mobile Evolution 15

2.4 Mobile Internet in 2G 17

2.5 i-Mode 17

3 EMERGING AND FUTURE APPLICATIONS AND SERVICES3.1 Future Mobile Service Needs 19

3.2 Location-based Services 193.3 3rd Party Services 19

4 ENHANCEMENTS TO 2ND GENERATION – “2.5G”4.1 GSM Enhancements 21

4.2 Circuit-Switched vs Packet-Switched Data in GSM 23

4.3 Circuit-Switched Upgrade to GSM: HSCSD 23

4.4 GPRS and Packet Data in GSM 25

4.5 GPRS is Assumed in UMTS 25

4.6 EDGE 27

5. RESULTING REQUIREMENTS FOR UMTS NETWORKS

5.1 Key Features Required of a 3G System 295.2 Service Creation Flexibility 31

6. STANDARDISATION PROCESSES6.1 Brief History of 3G Research 33

6.2 Resulting W-CDMA Proposals for UMTS 35

6.3 The IMT2000 “Family” 37

6.4 Global Harmonisation and 3GPP 39

6.5 3GPP Brief and Working Groups 41

6.6 3GPP Specifications Releases 43

6.7 3GPP2 and Other Related IMT2000 Family

Member Standardisations 45

7. SPECTRUM HARMONISATION7.1 History of Spectrum Planning 47

The Need for UMTS



1.1 Mobile “Generations”

Mobile Networks are commonly divided into three “generations”, with the

3rd Generation, of which UMTS is one such system, on the point of being launched inadvanced markets such as Japan, Finland and the Isle of Man.

1st Generation systems were analogue systems, designed with the simple aim of

making speech services available on the move. They included technologies such as

TACS (Total Access Communication System), NMT (Nordic Mobile Telephone) and

AMPS (Advanced Mobile Phone System). However, even these simple systems led to

annual market growth rates of 30-50%, leading to around 20 million subscribers by 1990.

However, quality was poor, capacity was low, as was reliability. Thus, as demand

grew, the current range of 2nd Generation systems were developed to take their

place. The most well-known of these systems are GSM (Global System for Mobile

Communications), cdmaOne, and the system known in the US simply as “TDMA”, or

by its standardisation label of “IS-136”. These systems were characterised by a move

to representing information digitally and brought the following broad changes:

• More consistent and reliable quality of speech

• Increased capacity/spectrum efficiency through more advanced modulation and

access schemes

• Easier implementation of advanced voice services, text messaging, fax, plus theaddition of basic access to data networks

• Enhanced security and fraud prevention

However, even in the move from 1st to 2nd Generation, the basic aim was still to

optimise for speech services delivered over wide areas (macro cells). 1st and 2nd

Generation systems are therefore all characterised by circuit switched networks, which

are well-suited to symmetric, real-time “conversational” services. The term 2.5G is

sometimes used to describe enhancements to 2nd Generation systems which aimed to

optimise parts of these systems for data applications using packet-switching techniques.

The latest move, to 3rd Generation, further advances digital systems with the

particular aim of increasing the ability to use data applications on the move

(i.e. mobile computing or the wireless office), and to enable “multimedia” services,

which may mix voice, graphics, video, music and so on. In order to achieve this, a

key change is in increasing the ability of mobile systems to transfer larger quantities

of information much faster.

A factor throughout the evolution of mobile (and all telecoms systems) has been the

constant improvement in semiconductor and microwave technologies. While such

changes are permitting smaller and more sophisticated mobile equipment to be built,they are also resulting in the expectation of users for more complex, data intensive

applications and services.

UnderstandingUMTS

1. MOBILE NETWORKS TODAY

The Need for UMTS

©Informa Telecoms1



3G

• digital

• multimedia

1980 1990 2000

data

optimised

2G

2.5G

• digital

• speech, fax, data

1G

• analogue

• speech

?speech

optimised

Trends:• functionality• reliability

• efficiency

• quality

3G

• digital

• multimedia• mainly

packet-

switched

1980 1990 2000 time

data

optimised

2G

2.5G

• digital

• speech, fax, data

• circuit-switched &

packet-switched1G

• analogue

• speech

• circuit-switched

speech

optimised

?

Fig. 1 – Evolution of Mobile Networks

2©Informa Telecoms



1.2 Mobile Network Basics

All mobile networks can be divided quite simply into three basic elements: the user

terminal, the radio access network and the core network.

The user terminal is the mobile element – the susbcriber’s handset. The radio access

network describes the series of base stations, which send and receive the radio

signals to and from the user terminals. Within this radio access network, there will

also be various elements which control these base stations.

The radio path between the base station infrastructure and the mobile terminals is

often referred to as the “air interface”.

The base stations are arranged such that each has responsibility for providing

a particular geographical area with radio coverage. These regions are known as“cells”, and hence such networks are often described as “cellular” networks. In a

perfect planning environment, an evenly spaced set of such base stations would

result in a series of interconnecting hexagonal cells, although in practice the real

shapes of these cells will vary.

The core network is a fixed telecoms network which interfaces the radio access

network with the rest of the telecoms world, be that other mobile networks, the

Internet, the Public Switched Telephone Network (PSTN) and so on. The core network

will include elements which manage the subscriber’s information and access, manage

the efficient running of the whole network, and the delivery of services through theradio access to the user.

UnderstandingUMTS

The Need for UMTS

©Informa Telecoms3



User Terminal

External

Network(e.g. fixed,PSTN,

Internet etc...)

Radio

Access

Network

Air

Interface

Core

Network

basestation

cells

User Terminal

Fig. 2 – Basic Mobile Network Elements

4©Informa Telecoms



1.3 The 2nd Generation Legacy

In order to understand the mobile environment into which UMTS and other

3rd Generation systems are designed to be launched, it is worth looking at the 2ndGeneration mobile systems in operation at the end of the 1990s.

These 2nd Generation networks break down into a number of major types. Each use

different technologies, and so handsets designed for one type of network will not

work in an area covered by the radio access network of another type. The table

shows the geographical usage, plus the different technologies used in both the air

interface and the core networks.

GSM is clearly the most widely used technology, whereas Personal Digital Cellular

(PDC) is used exclusively in Japan, and provides no capability to roam to other parts

of the world.

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The Need for UMTS

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Fig. 3 – Second Generation (2G) Systems

6

TDMA

GSM cdmaOne (IS-136) PDC

Europe

North America

South America

China

Japan

Asia Pacific

Air Interface Scheme TDMA/FDMA CDMA TDMA TDMA

Core Network GSM-MAP IS-41 MAP IS-41 MAP



1.4 Radio Access Schemes

In transmitting different signals within a given frequency allocation, there are two

basic ways in which this spectrum can be divided up.

FDMA (Frequency Division Multiple Access) schemes divide a spectrum allocation

into smaller frequency segments, allocating each signal a different frequency.

Simple 1st Generation systems used this method.

TDMA (Time Division Multiple Access) allows signals to be transmitted on the same

frequencies, but not at the same time – each signal is given its own time slot within

this frequency band.

Note that GSM uses a combination of both of these schemes. Network Operators are

allocated a portion of spectrum which is divided into radio carrier frequencies spaced200kHz apart (FDMA). Each carrier frequency band is then divided into eight separate

timeslots (TDMA).

The third type of access scheme, CDMA (Code Division Multiple Access), allows all

signals to share the same frequency and time domains. In order to distinguish signals

at the receiver, unique codes are attached to each signal.

A common analogy which is made between the TDMA and CDMA schemes which are

the basis of 2G cellular systems is as follows.

Imagine a crowded room. In a TDMA system, everyone in the room is speaking the

same language. Therefore in order to hear someone speaking on the other side of the

room, it is necessary for everyone else to stop speaking. Each person could therefore

be allocated a recurring timeslot during which they could speak, with multiple

conversations supported by allocating a different timeslot to each.

In CDMA, everyone in the room is speaking a different language. Therefore even

when other people in the room are speaking at the same time, it is still possible to

pick out what the person on the other side of the room is saying, so long as he is

speaking the language that you understand.

The different access schemes are illustrated opposite.

UnderstandingUMTS

The Need for UMTS

©Informa Telecoms7



Frequency Frequency Division

Time

Frequency Time Division

Time

User 1 User 2 User 3 User 1 User 2




User 3

User 2

User 1

Frequency Frequency and Time Division

Time

Frequency Code Division

User 1-?

Time

Fig. 4 – Radio Access Methods

8©Informa Telecoms



1.5 Focus in on GSM Network Elements

UMTS development was started in Europe, to build upon the GSM systems also

developed there. Thus it is instructive to focus in slightly more on the elements whichmake up GSM networks.

The radio access part of the network consists of a set of base transceiver stations

(BTSs) which provide the radio communication with the mobile handset. A group of

BTSs will be controlled by a Base Station Controller (BSC), with this combination of

BSC and BTS elements known as the Base Station Subsystem (BSS).

The radio access links in to the core network at an element known as the Mobile

Switching Centre (MSC). The GSM switching infrastructure is based on ISDN, and as

such, switches are designed to cope with data rates of up to 64kb/s. The MSC will

communicate with a number of databases, known as location registers, which give

the relevant information regarding the subscriber’s identity, the legality of the handset,

the subscribers current cell location and so on, allowing the MSC to switch and direct

services and traffic appropriately.

An overall Network Management function will also connect into the MSCs, to control

overall network operation.

A Gateway MSC can also be defined, and describes an MSC which provides access

between the core GSM network and another interconnected network,

such as PSTN, ISDN and so on.

UnderstandingUMTS

The Need for UMTS

©Informa Telecoms9



Other

Networks

RADIO

ACCESS

CORE

NETWORK

BSC

MSC

GMSC

Network

Management

USER

Databases

BTS BTS

Fig. 5 – Basic GSM Network Elements

10©Informa Telecoms



2.1 2G: A Changing Market

Although capacity limitations, and a need for new spectrum, are certainly major

factors for operators looking to deploy UMTS, new revenue opportunities throughnew services are seen as the key drivers.

2nd Generation in the most advanced markets at the end of the 1990s, can be

summarised as follows.

Very little further capacity remained available, resulting in busy signals, dropped calls,

and generally poor quality of service in busy areas. There was evidence of

a demand for data services shown by the rapid growth in basic SMS (text messaging)

traffic, and increased use of GSM for dial-up access to Internet and email while away

from the office. Technologies such as WAP were just emerging to further enable

mobile Internet services. At the same time, competition was driving profit margins on

plain voice subscribers down.

UnderstandingUMTS

2. MODERN MOBILE SERVICE NEEDS

The Need for UMTS

©Informa Telecoms11



Time

2G Network

Capacity

Payment based

on amount of data

or time connected

rather than content

Data rate

per user

constrained

by technology

Inefficient network/

technology require

large investmentsto increase capacity

Contribution

to Capacity

Requirements

Rapid subscriber

growth (dwindling

revenue per voice call)

Basic data

services

Mobile e-mail,

basic Internet

and other services

Fig. 6 – 2G and the Market Trends


• rapid subscriber growth

• dwindling spare capacity

• rapid growth of basic data services

• growth of mobile e-mail and basic Internet Access

• decreases in the price of voice services



2.2 General Trends in Telecommunications

As the 2G mobile market changed, so too were there changes taking place in

the fixed world.

In particular the Internet has become the de facto delivery method for a whole new

range of information and entertainment services to consumers, as PC ownership

grows. The continued increase in the ability of such PCs, increased modem speeds

and the introduction of faster fixed-line connections (e.g. ISDN, ADSL) means that

applications are becoming ever more data-hungry.

The result in fixed networks is that they are beginning to carry much more data traffic

than voice traffic, and again the revenues from the latter continues to decrease due to

competition.

At the same time, as users become used to being able to speak to each other when

on the move, and collect their email on the move, the natural desire is for mobility,

rather than be tied to fixed terminals and locations for other data applications as well.

UnderstandingUMTS

The Need for UMTS




Fig. 7 – “Fixed” Telecoms Trends


• Rapid growth in the

Internet

• Increasingly data-hungry

applications

• Data overtakes voice

traffic

• Prices for voice decrease

• Users want mobility



2.3 Mobile Evolution

Combining the state of 2nd Generation with the trends happening in the fixed and

Internet worlds, the obvious market conclusion is that there is huge potential for“Mobile Internet”, a bleak future for simple voice revenues, and an increasing need to

be able to access “desktop” applications from other terminals, including mobile ones.

UnderstandingUMTS

The Need for UMTS




Fig. 8 – Market Conclusions


• Huge potential for Mobile Internet

• Bleak future for voice (revenues)

• Access needed to desktop

applications when mobile



2.4 Mobile Internet in 2G

The first steps to “Mobile Internet” and mobile data using WAP and/or GSM data

cards met with mixed reviews. These reviews most commonly cited slow speed,unreliability and high cost as the key negatives.

Thinking back to the original aim of 1G and 2G mobile networks – optimised to

deliver real-time voice – it is not surprising that changes need to be made.

In 2G networks, access to the Internet involved dialling up for a connection, which

could take 10s of seconds, and then waiting for data to download at very slow

speeds (max. 14.4kb/s in GSM). If the radio signal was broken during this connection,

then dial-up would have to be done all over again. All this time, users would pay for

the length of the call, regardless of how much or how little data had actually been

received.

A key aim in defining 3G systems was therefore to allow faster speeds, to avoid the

constant need for dial-up, to give better quality, and to allow different charging

models, for instance based on the quantity of data transferred rather than the

time used, or maybe even to bill for content.

As well as enhancing the user experience, new systems which optimise the transport

of data (whilst preserving traditional voice quality), also contribute greatly to

increasing operational efficiency, spectrum usage and hence cost-savings for the

operators. The diagram opposite illustrates the changes required in moving from 2Gto 3G to optimise support for applications such as Mobile Internet.

2.5 i-Mode

Perhaps the first evidence that the new “Mobile Internet” could create huge demand

and hence new revenue streams, came from Japan.

NTT DoCoMo’s i-Mode service attracted over 10 million subscribers to its service

within the first year, with unexpectedly popular (and revenue-generating) services

including ring-tone and cartoon character download.

Even though the data rates associated with the service were still slow (only 9.6kb/s),

i-Mode used “packet-based” delivery to avoid dial-up, and kept services simple yet

attractive. One of the most important features of the i-Mode service was also in the

number of different services which were available, provided not by NTT DoCOMo

themselves, but by allowing access for a whole range of 3rd party developers. This

was the first time that any operator had built a business model which enabled such a

wide ranging service offering, and used the wider development community to provide

these services directly to their subscriber base.

UnderstandingUMTS

The Need for UMTS




Fig. 9 – Key Features of 3G in Support of the Mobile Internet


2G Mobile Internet New Needs in 3G (i-Mode)

slow dial-up avoid dial-up

slow downloads faster

unreliable guarantee quality

expensive new charging models

little choice wide range of services



3.1 Future Mobile Service Needs

In addition to evidence from existing applications and services, there have been a

number of market studies to try to identify key opportunities for the future.

Clearly it is difficult to predict with any accuracy which services will and won’t

succeed, and there will, of course, be entirely new services which are as yet not even

thought about. Thus a prime aim in developing UMTS and other 3G systems is to

provide the capability to be flexible and open in providing new services as they are

developed, whoever they may be developed by.

Some of the likely service groups are illustrated opposite. Those in bold indicate

services which it is impossible to offer on 2G systems with any degree of quality,

although obviously just about any service will benefit from the increases in data rate

(speed) and reliability which 3G will offer.

3.2 Location-based Services

A widespread belief is that the key applications will not be those simply ported from

the fixed world, but those which take advantage of the fundamental benefits of the

mobile phone. In particular, since the mobile device can change its location, services

which are tailored to this location (restaurant bookings, route finding, location

information, etc.) are seen as services with no fixed world competition.

(A * illustrates those services on the opposite page which could fall into this category.)

3.3 3rd Party Services

There is also plenty of activity from other sectors of industry such as banks and

retailers, who see the mobile phone very much as a “personal trusted device”, and

hence a key opportunity for transactions and commerce. It is also true of location

services such as navigation, that map information, for example, may be held by a

digital mapping company.

In most cases, operators will not be able to offer such services alone, but will

need to work with 3rd party content and service providers. In many cases, suchcollaboration will require inter-working, with an access route to 3rd party application

servers and databases located outside the operator’s own network.

Almost any of the Entertainment or Service opportunities could fall into this category.

UnderstandingUMTS

3. EMERGING AND FUTURE APPLICATIONS AND SERVICES

The Need for UMTS




Fig. 10 – Future Application & Service Needs


Web Browsing

Networked Games Consumer

Music Downloading Entertainment

Mobile Video Clips

Mobile Shopping*Mobile Banking* Consumer

Information Services

(timetables, hotels, tourist etc.)*Navigation*

Video Telephony

Picture Mail Communication

Multimedia Messaging

Video Conferencing

Intranet Access

Corporate Database Access Corporate

Business Information

(stocks, news, salesforce etc.)*

Telematics*Remote Metering & Security* Machine-to-Machine

Wireless Vending

Bold services which need 3G for sufficient speed and quality

* services which may be location based



4.1 GSM Enhancements

2nd Generation standards have of course continued to evolve through the years since

the first networks were launched back in the early ’90s. This is particularly true ofGSM, for which UMTS is the next step.

In particular GSM900 standardisation was completed by ETSI in 1990 (Phase 1) but

enhanced in a Phase 2 set of standards in 1995, with further Phase 2+ releases in

1996, 1997, 1998 and 1999.

As a result, GSM is now designed to support a number of advanced voice services

(call waiting, call forwarding, international roaming and so on), and can also support

basic data services and fax. In particular SMS, the store-and-forward Short Message

Service, was specified in GSM and has led to a recent explosion in text messaging

traffic over GSM networks.

Three new technologies in particular were standardised in the last releases of the

GSM standard: High Speed Circuit Switched Data (HSCSD), Enhanced Data Rates

for Global Evolution (EDGE) and General Packet Radio Service (GPRS). All were

designed with the enhancement of data traffic over GSM networks in mind.

Most recently, the introduction of the Wireless Application Protocol (WAP) standard,

which uses the Wireless Markup Language (WML), a derivation of the Internet

application programming language Hyper Text Markup Language (HTML), has led to

services enabling access to the Internet over mobile phones. Although not a part ofGSM standardisation itself, WAP was important in that it provided a general mobile

application-level enhancement which could help make the most of the service

delivery capabilities of the GSM transport enhancements above.

UnderstandingUMTS

4. ENHANCEMENTS TO 2ND GENERATION – “2.5G”

The Need for UMTS




Phase 1 (1990) Basic Service Operation

Phase 2 (1995) Supplementary services

comparable to ISDN

Phase 2+ (1996 – 1999) Advanced features, e.g:

• IN (CAMEL)

• Enhanced Speech

• Higher Data Rates

• Transport

enhancements:

HSCSD, GPRS,

EDGE

Fig. 11 – The Evolution of GSM




4.2 Circuit-Switched vs Packet-Switched Data in GSM

Circuit and packet-switched data are conceptually illustrated opposite.

In the diagram 1, a conversation or data transfer between users 2 and 3 is achieved

by defining and reserving a transport “pipe” between them. All the time that this pipe

is open, it is impossible to transfer data between two other users (1 and 4) who would

need to use elements of the same route through the network. More resources, or

pipes, would need to be provisioned between the switches to cater for the additional

requirement, since the pipes themselves (or “circuits”) cannot usually be shared.

In the lower diagram, the data to be transferred between users 3 and 2 is divided into

discrete packets which pass through the network. However, at no time is the whole

route between the two users completely filled, hence user 4 can also send packets of

data to user 1 during the same overall time period, using the gaps left between

packets sent by user 3. In real networks, it is possible to send different packets

on entirely different routes through the network, depending on resources available.

This does however mean that special efforts need to be made in cases where it is

important for the different packets to arrive in a particular, time-sensitive sequence.

In keeping open a dedicated circuit for the duration of a call, circuit-switched data

transport has some advantages for some applications, in reserving the bandwidth for

the duration of the call and ensuring real-time communication. Thus for certain

symmetrical applications (where traffic passes at the same rate in both directions),

e.g. voice or video telephony, there can be a benefit.

However, in a situation where the amount of data being sent between users is limited,

and/or transmission is intermittent, or “bursty”, it is much more efficient to use these

“silent” periods to enable other users to send data over the network. Thus, in general,

packet-based systems will allow much more efficient use of the network resources.

4.3 Circuit-Switched Upgrade to GSM: HSCSD

Circuit-switched user data transport in GSM, initially at 9.6 kb/s, has been enhanced

to 14.4 kb/s, and up to as much as 56kb/s using HSCSD. HSCSD works by allocatingup to four time slots to a single user in GSM’s TDMA scheme.

For the first time, HSCSD enables GSM circuit-switched connections to be

asymmetric, by allocating a different number of timeslots in the downlink connection

(to the mobile) than in the uplink (from the mobile).

HSCSD does not require any entirely new elements to be added to a GSM network,

but can be implemented by upgrading handsets and existing elements, including

transport schemes.

UnderstandingUMTS

The Need for UMTS




USER 1

USER 2Network

Switches USER 3

USER 4

1) Circuit-switching: – up to 57.6kb/s using HSCSD

USER 1

USER 2Network

Routers USER 3

USER 4

2) Packet-switching: – up to 115.2kb/s using GPRS

I Data Transferred 3➝2

I Data Transferred 4➝1

Fig. 12 – Circuit Switched vs Packet Switched Data




4.4 GPRS and Packet Data in GSM

GPRS adds a packet-based transport capability to the GSM system, and brings

IP networking into the GSM world. As well as modifications within handsets andtransport channel schemes, GPRS also involves the addition of new packet routers

into the GSM core network, producing a core network with separate circuit and

packet-switched domains.

These routers are the Serving GPRS Support Node, which is the packet equivalent

of the MSC, and the Gateway GPRS Support Node, the equivalent to the GMSC.

Since we have seen that packet-switching operates with no need to keep an

end-to-end bandwidth reservation for the full duration of the information transfer, this

is particularly important in radio systems. Using GPRS, radio resources are only

required as each packet of information is sent or arrives, not for the entire duration

of the data transfer.

Also, since no dial-in is required in order to transfer data over an all packet network

(since no circuit setup is required), the term “always on” is sometimes applied to

describe networks like GPRS.

In the circuit-switched domain, data rates are limited by the capability of the

MSC switches, to 64kb/s. In theory GPRS is capable of user data rates up to

115.2kb/s, although actual field trials and early commercial services suggest that

rates of around 20-30kb/s are more realistic under real conditions.

4.5 GPRS is Assumed in UMTS

Although in terms of data rates GPRS is certainly not capable of delivering many of

the perceived 3G services, it does provide an enhanced 2G network which now has

both circuit and packet-switched capability.

Thus the first release of the UMTS standard assumes that operators start from a point

where GPRS is implemented, and that these operators already have both these circuit

and packet-switched domains in their network. HSCSD is not part of the

specifications within UMTS, and is simply an option for operators to upgrade the

circuit-switched domain.

UnderstandingUMTS

The Need for UMTS




RADIO

ACCESS

CORE

NETWORK

BSC

PCU

MSCSGSN

GMSCGGSN

Databases,

Network

Management

USER

Other Network(s)

(“ The Internet

or Intranets” )

Other Network(s)

(“ The PSTN

or ISDN” )

“Circuit-Switched”

(dial-up)

“Packet-Switched”

(always-on)

BTS BTS

Fig. 13 – Addition of GPRS to GSM




4.6 EDGE

EDGE is a technology at the air interface to GSM, which provides an improved

modulation scheme and improves spectrum efficiency. EDGE uses 8 Phase Shift Keyingrather than standard GSM Gaussian Minimum Shift Keying. This has the effect of

increasing data rates, with rates as high as 384kb/s in a 200KHz GSM carrier (for 4

Timeslot GPRS operation). It involves no core network changes, although many see its

main use in combination with the changes to deliver high data rates using a GPRS core.

A variation of EDGE has also been defined for use with US-TDMA (IS-136) systems.

In this context, EDGE is seen very much as a 3G radio access technology in its own

right, since it is capable of delivering 3rd Generation data rates. An advantage of

EDGE as a 3G technology is that it does not require any further spectrum for

operators. The use of a common air interface technology in both IS-136 and GSM

networks is also seen as a possible route to allow convergence and roaming between

these two network types.

The UMTS system makes no assumption that EDGE will be present in the 2nd

Generation network from which UMTS evolves, although the continued standardisation

of GERAN (GSM EDGE Radio Access Network) has now been moved within the same

standardisation body in order to ensure future interoperability between UMTS and

EDGE radio access schemes. Such interoperability will be important in situations

where UMTS is rolled out as “islands” of coverage in the early stages, since EDGE

can help to deliver high data rates through the “sea” of GSM/GPRS which surround

these UMTS islands.

UnderstandingUMTS

The Need for UMTS




Radio

Access

Network

Core

Network

EDGE Replaces

GSM Radio

Modulation

Fig. 14 – EDGE


• Changes to radio Interface only (8PSK instead of GMSK for GSM)

• Involves no new spectrum

• Can support “3G-like” data rates (384kbp/s user rate)

• Also defined for use in IS-136 TDMA systems

• Possible “fill-in” technology during early UMTS rollout

• Can be combined with GPRS for enhanced services



5.1 Key Features Required of a 3G System

Despite the enhancements to 2G networks, it remains the case that many of the

“future services” require higher data rates than available even with “2.5G”. In addition,the future mix of services remains virtually unknown. Therefore, planning needs to be

flexible, and both circuit and packet-switched domains need to be supported.

The ITU, through its IMT2000 initiative, began the process of trying to describe the

required capabilities of a 3rd Generation system, with groups such as the UMTS

Forum continuing to develop such market requirements. We can compile the key

feature requirements of the UMTS system as follows:

1. Higher data rates, up to 2Mb/s, to enable applications such as large file transfers,

mobile video and music, and so on.

2. Multimedia service support. The ability to multiplex voice, data, video and other

services on a single connection, to be received simultaneously.

3. Flexibility – the ability to request “bandwidth on demand”, and variably set data

rates to suit applications in progress.

4. Efficient delivery of asymmetric services, such as web browsing. This requires the

enabling of different bit rates on the uplink and downlink.

5. Quality of Service control, with guarantees over a range from real-time, low loss

services like speech down to “best effort” services.

6. IP support, to enable efficient interworking with the Internet and other IP-based

applications.

7. Coexistence and interworking with existing 2nd Generation networks (GSM) and

services, in which operators have already invested a huge amount.

8. Ease of global harmonisation, in order to ensure that users can gain access to their

services wherever they are.

UnderstandingUMTS

5. RESULTING REQUIREMENTS FOR UMTS NETWORKS

The Need for UMTS




UMTS

High Data Rates

FlexibilityCompatibility

with the Internet

Multimedia

Support

Coexistence

with 2G (GSM)

Efficient Support for Asymmetric Services

QoSGuarantees

Fig. 15 – Requirements for UMTS




5.2 Service Creation Flexibility

The process of Service Creation is also something which has been paid much

attention in developing UMTS.

One of the key successes of the Internet has been to allow 3rd party application

developers, be they big software corporations or simply single entrepreneurs with a

good idea, to easily create applications and services which can be accessed by

anyone, anywhere. In contrast, the world of mobile communications has been

dominated by closed systems and system-defined services, which made it difficult for

companies independent from the operator to add to.

That said, the success of i-Mode, with its myriad of 3rd party content and

applications providers, seemed to show that variety would also succeed in mobile.

Enhancements to GSM recently included SIM Application Toolkit (SAT) and CAMEL,

both of which were designed to provide open “toolkits” whereby 3rd party developers

can develop applications, safe in the knowledge that they will run on the networks

and handsets of any operators supporting SAT & CAMEL. MExE is another such

toolkit, which draws together WAP & Java into a similarly standardised creation

environment.

UnderstandingUMTS

The Need for UMTS




Camel

SAT

MExE

Internet

Standardised

Services

• Standardised Service Capabilities

• Service Development Toolkits

GSM

UMTS

Fig. 16 – Service Creation in UMTS




6.1 Brief History of 3G Research

The ITU coined the term “International Mobile Telephony 2000” (IMTS 2000) to refer

to an envisaged scenario whereby mobile users would have a single systemworldwide, giving them access to a much larger array of services, including seamless

convergence with the services they had available on their fixed (and satellite)

networks. The original ITU goal was to drive development of a single standard

worldwide for 3rd Generation mobile, avoiding the problems currently, when trying to

roam between different countries. IMT2000 is also referred to in some early papers as

FPLMTS (Future Public Land Mobile Telecommunications System).

Of course research and development into the 3rd Generation had already started

elsewhere, as early as the start of the 1990s, in order to build on GSM and the other

2nd Generation systems around the world. The concentration of this work was on

improving the efficiency of the radio interface, in order to better utilise scarce

spectrum resources.

In Europe, EU projects in RACE I & RACE II (Research for Advanced Communication

Technologies in Europe), in particular CODIT (Code Division Testbed), and ACTS

(Advanced Communication Technologies and Services), in particular FRAMES (Future

Radio Wideband Multiple Access System), eventually led to the choice of the 3rd

Generation air interface within ETSI. In fact a number of systems were proposed to

ETSI, with the eventual choice of a radio technology known as Wideband CDMA

(W-CDMA) for the UMTS radio interface being decided on the basis of best fit with

the ITU’s IMT2000. In this respect the earlier decision by Japan’s standardisation

body ARIB (Association of Radio Industries and Businesses), to choose a W-CDMA

radio interface for 3G was a strong factor, since it brought the promise of greater

global harmonisation.

Following early development work within ETSI, the development and specification

work was passed over to a global group known as the 3rd Generation Partnership

Project (3GPP).

UnderstandingUMTS

6. STANDARDISATION PROCESSES

The Need for UMTS




time

1992 1995 1997 1998 1999 2000

GLOBAL

EUROPE

JAPAN

RACE 1 RACE 2 ACTS

Specification

work goes to 3GPP

ETSI select

W-CDMA

ARIB selectW-CDMA

Standards:

Release ’99

ETSI

“Raw

Specifications”

1988

EURESEARCH

Fig. 17 – Development of W-CDMA




6.2 Resulting W-CDMA Proposals for UMTS

The W-CDMA proposal which was born out of these various research efforts brought

the following key changes from the GSM radio interface, in order to meet the servicerequirements for 3G.

1. Carrier spacing (bandwidth): 5MHz vs. 200KHz.

The wider bandwidth available to W-CDMA means that much more information can

be sent, and that data rates can be much quicker. Indeed, in theory, the specification

allows data rates of up to 2Mb/s in the packet-switched, and up to 384kb/s in the

circuit-switched domains.

2. Negotiation of radio bearer properties to suit different QoS requirements.

In W-CDMA, quality is controlled as part of radio resource management, with radio

resources applied to suit a particular application/user need. In GSM, quality was more

a result of network and frequency planning, since all applications had access to the

same physical radio transport properties.

3. Two coexisting modes: FDD & TDD

These refer to the way uplink and downlink signals are separated. FDD (Frequency

Division Duplex) is likely to be the most commonly applied mode in early UMTS

deployments, and is suited to wide area mobility, whereas TDD (Time Division Duplex)

allows higher data rates to be more efficiently offered over limited distances, such as

in small urban cells.

UnderstandingUMTS

The Need for UMTS




• 5MHz Carrier

Spacing

• QoS Negotiation

of Radio Resources

• Two Main Modes

of Operation

f fn+1fn 5MHz Spacing

(User Data up to 2Mb/s)

Radio Resource Info

QoS Negotiation

FDD TDD

Uplink

Downlink

Same Frequency for

Uplink and Downlink

Separate

Frequencies

Fig. 18 – W-CDMA: Key Features




6.3 The IMT2000 “Family”

In parallel with W-CDMA, the cdmaOne community were developing their next

generation system (cdma2000), and the IS/UWC-136 community were lookingtowards EDGE as a solution to its own 3G needs. Thus, a situation whereby a single

global standard might exist became both politically and technically unlikely.

After pressure from global operator groups represented by the OHG (operators

harmonisation group), some compromises were reached, resulting in the ITU’s

announcement of a “family concept” for IMT2000 terrestrial radio interfaces. The

approach is designed to be modular, and based on the admission that one standard

does not fit all the various regional requirements. Nevertheless, in designing as much

commonality between functions and modules as is feasible, IMT2000 is still designed

very much with global interworking as an easily achievable feature.

In particular, the following IMT2000 systems were defined:

TDMA-based systems:

i. Single Carrier TDMA

(also referred to as UWC-136, the evolution of the 2nd Generation standard

IS-136/TDMA)

ii. Multi-Carrier TDMA

(ETSI’s DECT standard for cordless telephony)

CDMA-based systems:

i. Direct Spread CDMA

(UTRA* FDD mode, often referred to simply as “W-CDMA”)

ii. Multi-Carrier CDMA

(also known as cdma2000, the evolution of the 2nd Generation standard

cdmaOne/IS-95)

iii. TDD mode(UTRA TDD, to be further harmonised with a standard supported by China,

known as TD-SCDMA)

(*UTRA = UMTS Terrestrial Radio Access)

UnderstandingUMTS

The Need for UMTS




DECT2G

Multi-Carrier

TDMA

“DECT”

TDMA

(IS136)

Single Carrier

TDMA

“UWC136”

“EDGE”

GSM

Evolution Paths

DS-CDMA

“UTRA-FDD”

TDD-Mode

CDMA

“UTRA-TDD”

cdmaOne

(IS95)

Multi-Carrier

CDMA

“cdma2000”

IMT2000

TDMA Family CDMA Family

“W-CDMA”

Fig. 19 – IMT2000 Family




6.4 Global Harmonisation and 3GPP

In addition to the creation of the IMT2000 family concept, the major result of the

recognition of the need for a global, collaborative effort to standardisation was theformation of the “3rd Generation Partnership Projects” (3GPP).

Clearly there was no benefit in regions each developing their own versions of a

W-CDMA standard, for example the parallel work on ARIB and ETSI, so the first

group, 3GPP, was brought together to ensure that specifications were developed from

a global perspective. These specifications were then turned into standards by each of

the standards bodies.

3GPP has the following Standards Development Organisation (SDO) Partners:

• ETSI (Europe) – European Telecommunications Standards Institute

• CWTS (China) – China Wireless Telecommunications Standard Group

• ARIB & TTC (Japan) – Association of Radio Industries and Businesses and

Telecommunications Technology Commission

• TTA (Korea) – Telecommunications Technology Association

• T1 (USA) – Sponsored by the Alliance for Telecommunications Industry Solutions,

and accredited by the American National Standards Institute.

In addition to SDO partners, 3GPP also as a number of “market representation

partners”, to ensure that the specifications are developed very much in order to meet

market needs. The MRPs in 3GPP are (Fig. 20):

• GSA (GSM Suppliers Association, representing GSM equipment vendors)

• GSM Association (representing the GSM industry, operators in particular)

• UMTS Forum (representing all spectrums of interest in UMTS development)

• IPv6 Forum (representing those driving the introduction of IPv6, the next generationInternet standard)

• 3G.IP (an operator-led initiative driving for a common 3G network architecture,

e.g. to enable interoperability between fixed and mobile)

• UWC (Universal Wireless Communications, representing the IS-136 Industry)

• MWIF (Mobile Wireless Internet Forum, an initiative seeking a single mobile wireless

and Internet architecture, independent of access technology)

UnderstandingUMTS

The Need for UMTS




Fig. 20 – 3GPP


Standards Development

Organisation Partners

ETSI

CWTS

ARIB

TTC

TTA

T1

Market Representation

Partners

GSA

GSM Association

UMTS Forum

IPv6 Forum

3G.IP

UWC

MWIF



6.5 3GPP Brief and Working Groups

3GPP’s brief is to develop a 3G system based on the evolved GSM core network,

and the UTRA FDD & TDD modes (i.e. UMTS). It is also now responsible for thefurther specifications of EDGE.

Within 3GPP, work is split into the following subgroups, representing each of the key

elements of UMTS specification:

• Radio Access Network (TSG RAN)

• Core Network (TSG CN)

• Services and System Aspects (TSG SA)

• Terminals (TSG T)

Plus

• GSM EDGE Radio Access Network (TSG GERAN)

Co-ordination of the different groups is performed within the overall Technical

Steering Group (TSG).

UnderstandingUMTS

The Need for UMTS




TSG

Radio

Access

Network

Core

Network

GSM EDGE

Radio

Access

Network

Terminals

Services &

System

Aspects

3GPP

Fig. 21 – 3GPP Working Groups




6.6 3GPP Specifications Releases

Although ETSI SMG had produced “raw” UMTS specifications at the end of 1998, the

definition of the first set of useable and public specifications came out of 3GPP at theend of 1999, with some modifications in March and June 2000.

This was the so-called “Release ’99”, which very much defines the first steps in

implementing UMTS from the starting point of an enhanced GSM/GPRS network.

In particular, Release ’99 concentrates on the implementation of a new radio interface

system (UTRAN).

Other key differences between the first set of 3GPP specifications (Release ’99) and

GSM are as follows:

• Support for Higher Data Rates

• Multiplexing services to a single user

• Bearer flexibility – the ability to choose appropriate radio resources to suit the

application/user requirements.

• Improved security

• Support for Multimedia Messaging

• Improvements in the Service Creation Environment

Release ’00 concentrates much more on the core network for UMTS, and in particular

the process of evolution towards all-IP systems. The eventual goal of most in the

industry is to avoid the split of transport between separate circuit and packet

domains, combining both onto a single IP-based packet network once appropriate

QoS control is possible.

It has been decided that rather than stick to regular yearly releases of standards,

these will instead be released whenever useful content batches are completed. Thus

future releases will be referred to by number. In this context, release (R’00) is known

as R’4.

UnderstandingUMTS

The Need for UMTS




Fig. 22 – Highlights of Specification Releases


GSM

3GPP Release ’99• New radio access

• Higher data rates

• Multiplexed services

• Bearer flexibility

• Improved security

• Multimedia messaging• Improved service creation

3GPP Release ’00/Release 4

• Core network evolution to all-IP



6.7 3GPP2 and Other Related IMT2000 Family Member Standardisations

A parallel partnership project, 3GPP2, was created to harmonise worldwide

specifications of the cdma2000 (MC-CDMA) aspects of the IMT2000 family.

Other harmonisation goals for 3rd Generation are the desire to be able to attach

UTRA to IS-41 core networks (currently used in 2nd Generation cdmaOne and

TDMA/IS136 systems), or to attach cdma2000 radio access to GSM core networks.

Thus, there is certainly co-operation between 3GPP and 3GPP2 to be expected.

In terms of the other IMT2000 interfaces, US standardisation groups continue to work

on the single carrier TDMA mode, and ETSI on multi-carrier TDMA (DECT). IMT2000

development work is illustrated opposite.

UnderstandingUMTS

The Need for UMTS




Fig. 23 – Development within IMT2000


DS-CDMA & TDD-CDMA 3GPP (Global Partnership)

(UTRA FDD & TDD)

MC-CDMA (cdma2000) 3GPP2 (Global Partnership)

MC-TDMA (DECT) ETSI (Europe)

SC-TDMA TR45.3 (Part of TIA) (US)



7.1 History of Spectrum Planning

One of the key planks in the ITU desire for 3rd Generation systems to be seamless

globally, is the provision of spectrum. In particular, it is clearly easier to implement asystem globally if spectrum bands are the same in all the different regions of the

world.

Unfortunately this is not currently the case. In particular, the US PCS spectrum

allocations are at odds with the rest of the world and with no immediate prospect

of rearrangement.

The spectrum allocations for IMT2000, including UMTS, were first discussed as far

back as 1992, where some common bands were defined (except for the US). More

recently, the World Radio Conference (WRC2000) meeting in Istanbul, in May 2000,

allocated further spectrum for future IMT2000 use. This was in response to lobbying

by groups such as the UMTS Forum and GSM Association to increase the amount of

spectrum assigned to 3rd Generation systems, on the basis that capacity constraints

would once again be reached quickly, should the services take off as hoped.

The end result of negotiations was a spectrum map as shown opposite.

The key points to take away from this diagram are as follows:

• Continued lack of harmonisation between the US and rest of the world for most of

the spectrum band, although the 1710 – 1885 MHz IMT2000 band is common to allregions [although currently used by GSM1800 in some]

• Extra spectrum bands assigned to IMT2000 by the WRC2000 meeting, including

the 2500 – 2690 MHz band in all regions

• The split between uplink and downlink frequency bands for the FDD mode of

UMTS, and the location of TDD mode frequency bands. There is a current lack of

any TDD component for 3G in Japan.

In addition some regions have expressed particular preferences, for example:

• The US may implement IMT2000 at around 700MHz

• China prefers the range 2300 – 2400MHz for IMT2000 (and possibly its

own standard)

UnderstandingUMTS

7. SPECTRUM HARMONISATION

The Need for UMTS




I M T

2 0 0 0

U / L

I M T

2 0 0 0

D / L

W R C 2 0 0 0

8 0 6

9

6 0

8 0 0

9 0 0

1 0 0 0

2 5 0 0

2 6 0 0

2 7 0 0

1 7 0 0

1 8 0 0

1 9 0

0

2 0 0 0

2 1 0 0

2 2 0 0

W R C 2 0 0 0

1 7 1 0

1 8 8 5

W A R C 9 2

2 0 2 5

2 1 1 0

2 1 7 0 2 2 0 0

2 5 0 0

2 6 9 0

1 9 8 0 2 0 1 0

W A R C 9 2

W R C 2 0 0 0

M S S -

M o

b i l e S a

t e l l i t e

S y s

t e m

f r e q

( k H z

)

I M T 2 0 0 0

I M T 2 0 0 0

I M T 2 0 0 0

I M T

2 0 0 0

I M T

2 0 0 0

M S S

M S S

I M T

2 0 0 0

G S M

9 0 0

G S M

1 8 0 0

U M

T S

1 8 0 0

U M T S

S A T

D E C T

U M T S U N P A I R E D

U M T S P A I R E D

D / L

8 9 0

9 6

0

1 7 1 0

1 8 8 0

1 9 2 0

1 9 8 0 2 0 1 0 2 0 2 5

2 1 1 0

2 1 2 0

2 2 0 0

U M T S

S A T

1

9 2 0

1 8 5 0

1 9 3 0

1 9 1 0

1 9 1 0

1 9 8 0

2 1 1 0

2 1 7 0

P H S

R E S E R -

V E D

P C S

U / L

C E L L -

U L A R

P C S

D / L

S S

S S

1.Need for Umts

Documents

Transcript of 1.Need for Umts