1

IMT-2000 and UMTSThe Third Generation Mobile System

2

IMT-2000• IMT-2000 stands for IMT: International Mobile Communications 2000: the frequency range of 2000 MHz and the year 2000

• In total, 17 proposals for different IMT-2000 standards were submitted by regional SDOs to ITU in 1998. 11 proposals for terrestrial systems and 6 for mobile satellite systems (MSSs).

• All 3G standards have been developed by regional standard developing organizations (SDOs).

• Evaluation of the proposals was completed in 1998, and negotiations to build a consensus among different views were completed in mid 1999. All 17 proposals have been accepted by ITU as IMT-2000 standards. The specification for the Radio Transmission Technology (RTT) was released at the end of 1999.

3

IMT-2000

• The (IMT-2000), consists of 3 operating modes based on Code Division Multiple Access (CDMA) technology.

• 3G CDMA modes are most commonly known as:– CDMA2000,– WCDMA (called UMTS) and– TD-SCDMA

(Time Division-Synchronous Code Division Multiple Access)

4

IMT-2000The main characteristics of 3G systems, known collectively as IMT-2000, are a single family of compatible standards that have the following characteristics:

• Used worldwide

• Used for all mobile applications

• Support both packet-switched and circuit-switched data transmission

• Improved system capacity (traffic handling)

• Backward compatibility with second-generation (2G) systems

• Offer high data rates up to 2 Mbps (depending on mobility/velocity)

• Offer high spectrum efficiency

5

High-Speed Packet Data Services

• 2 Mbps in fixed or in-building environments (very short distances, in the order of metres)

• 384 kbps in pedestrian or urban environments

• 144 kbps in wide area mobile environments

• Variable data rates in large geographic area systems (satellite)

6

Multiple Standards for Different Applications and Countries

7

Towards 3G

8

UMTSUMTS is being developed by Third-Generation Partnership Project (3GPP), a joint venture of several SDOs (Standard Developing Organisations).

• ETSI (Europe)

• Telecommunication Technology Committee (TTC) (Japan)

• American National Standards Institute (ANSI) T-1 (USA)

• Telecommunications Technology Association (TTA) (South Korea)

• Chinese Wireless Telecommunication Standard (CWTS) (China)

To reach global acceptance, 3GPP is introducing UMTS in releases. The first release (UMTS Rel. ´99) defines enhancements and transitions for existing GSM networks.

9

GSM Mobile Communications The GSM 1800, DECT and UMTS Bands

1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200 2250

75 MHz

UMTSGSM 1800

DECT

1: Time Division Duplex (TDD)2: Frequency Division Duplex (FDD)3: Mobile Satellite System (MSS)

Uplink Downlink

Duplex Distance 95 MHz

75 MHz

1 2 3 1 2 3

Uplink60 MHz

Downlink60 MHz

10

11

Network Elements from UMTS

UMTS differs from GSM Phase 2+ (GSM +GPRS) mostly in the new principles for the air interface transmission

WCDMA instead of TDMA/FDMA

Therefore a new RAN (Radio Access Network) called:

UTRAN (UMTS Terrestrial Radio Access Network) must be introduced with UMTS

Only minor modifications are needed in the CN (Core Network) to accommodate the change

12

UTRA: UMTS Terrestrial Radio AccessThe most significant change in REL. ´99 was the “UTRAN”, a W-CDMA radio interface for land-based communications.

UTRAN supports time (TDD) and frequency division duplex (FDD).

The TDD mode is optimized for public micro and pico cells and unlicensed cordless applications.

The FDD mode is optimized for wide-area coverage, i.e. public macro and micro cells.

Both modes offer flexible and dynamic data rates up to 2 Mbps.

13

UMTS architectureUTRAN (UTRA NETWORK)

• Radio Network Subsystem (RNS)

UE (User Equipment)

CN (Core Network)

Uu Iu

CNUTRANUE

14

UTRANTwo new network elements are introduced in UTRAN

• RNC

• Node B

UTRAN is subdivided into individual radio network systems (RNSs), where each RNS is controlled by an RNC.

The RNC is connected to a set of Node B elements, each of which can serve one or several cells.

UTRAN architecture

UTRAN comprises several RNSs

Node B can support FDD or TDD or both

RNC is responsible for handover decisions requiring signaling to the UE

Cell offers FDD or TDD

RNC: Radio Network ControllerRNS: Radio Network Subsystem

Node B

Node B

RNC

Iub

Node B

UE1

RNS

CN

Node B

Node B

RNC

Iub

Node B

RNS

Iur

Node B

UE2

UE3

Iu

16

UTRAN functions

• Admission control• Congestion control• Radio channel encryption• Handover• Radio network configuration• Channel quality measurements• Radio resource control• Data transmission over the radio interface• Outer loop power control (FDD and TDD)• Channel coding

Core network

BTS

Node B

BSC

Abis

BTS

BSS

MSC

Node B

Node B

RNC

Iub

Node BRNS

Node B SGSN GGSN

GMSC

HLR

VLR

IuPS

IuCS

Iu

CN

EIR

GnGi

PSTN

AuC

GR

The Core Network (CN) and the Interface Iu, are separated into two logical domains:

qCircuit Switched Domain (CSD)• Circuit switched service incl. signaling• Resource reservation at connection setup• GSM components (MSC, GMSC, VLR)• IuCS

qPacket Switched Domain (PSD)• GPRS components (SGSN, GGSN)• IuPS

Access method CDMA

•CDMA (Code Division Multiple Access)–all terminals send on the same frequency probably at

the same time and can use the whole bandwidth of the transmission channel

–each sender has a unique random number, the sender XORs the signal with this pseudo random number

–the receiver can “tune” into this signal if it knows the pseudo random number, tuning is done via a correlation function

19

Base stationMs I sends: 0 1

CDMA, an example

Generate the chip Stream

00011011

1110010000011011

Base stationMs II sends: 1 1 Generate the chip Stream

11010001

1101000111010001

Spreading and scrambling of user data

• Constant chip rate of 3.84 Mchip/s

• Different user data rates supported via different spreading factors– higher data rate: less chips per bit and vice versa

• User separation via unique, quasi orthogonal scrambling codes– users are not separated via orthogonal spreading codes– much simpler management of codes: each mobile can use the same

orthogonal spreading codes

data1 data2 data3

scramblingcode1

spr.code3

spr.code2

spr.code1

data4 data5

scramblingcode2

spr.code4

spr.code1

sender1 sender2

Length

Length

SPREADING FACTOR

3.84 Mchip/s

• Sender A

– sends Ad = 1, key Ak = 010011 (assign: „0“= -1, „1“= +1)

– sending signal As = Ad * Ak = (-1, +1, -1, -1, +1, +1)

• Sender B

– sends Bd = 0, key Bk = 110101 (assign: „0“= -1, „1“= +1)

– sending signal Bs = Bd * Bk = (-1, -1, +1, -1, +1, -1)

• Both signals superimpose in space

– interference neglected (noise etc.)

– As + Bs = (-2, 0, 0, -2, +2, 0)

• Receiver wants to receive signal from sender A

– apply key Ak bitwise (inner product)

Ae = (-2, 0, 0, -2, +2, 0) • Ak

(-2, 0, 0, -2, +2, 0) • (-1, +1, -1, -1, +1, +1)= 2 + 0 + 0 + 2 + 2 + 0 = 6

•result greater than 0, therefore, original bit was „1“

– receiving B

Be = (-2, 0, 0, -2, 2, 0) • Bk

( -2, 0, 0,- 2,- 2, 0) • (1, 1, -1, +1, -1, +1) = -6, i.e. „0“

CDMA in theory

CDMA on signal level Idata A

key A

signal A

data ⊕ key

key sequence A

Real systems use much longer keys resulting in a larger distance between single code words in code space.

1 0 1

10 0 1 0 0 1 0 0 0 1 0 1 1 0 0 1 101 1 0 1 1 1 0 0 0 1 0 0 0 1 1 0 0

Ad

Ak

As

Here the binary ”0” is assigned a positive value,The binary ”1” a negative value!

CDMA on signal level IIsignal A

data B

key Bkey

sequence B

signal B

As + Bs

data ⊕ key

1 0 0

00 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 111 1 0 0 1 1 0 1 0 0 0 0 1 0 1 1 1

Bd

Bk

Bs

As-1+1

+1

-1

-2

0

+2

CDMA on signal level III

Ak

(As + Bs) * Ak

integratoroutput

comparatoroutput

As + Bs

data A

1 0 1

1 0 1 Ad

-2

0

+2

-20

+2

1

-1

CDMA on signal level IV

integratoroutput

comparatoroutput

Bk

(As + Bs) * Bk

As + Bs

data B

1 0 0

1 0 0 Bd

comparatoroutput

CDMA on signal level V

wrong key K

integratoroutput

(As + Bs) * K

As + Bs

(0) (0) ?

-2

0

+2

-2

+2

0

OSVF coding

1

1,1

1,-1

1,1,1,1

1,1,-1,-1

X

X,X

X,-X 1,-1,1,-1

1,-1,-1,11,-1,-1,1,1,-1,-1,1

1,-1,-1,1,-1,1,1,-1

1,-1,1,-1,1,-1,1,-1

1,-1,1,-1,-1,1,-1,1

1,1,-1,-1,1,1,-1,-1

1,1,-1,-1,-1,-1,1,1

1,1,1,1,1,1,1,1

1,1,1,1,-1,-1,-1,-1

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

SF=n SF=2n

...

...

...

...

Ortogonal Variable Spreading Factor Codes

Recursive rule

Support of mobility: macro diversity

• Multicasting of data via several physical channels– Enables soft handover– FDD mode only

• Uplink– simultaneous reception of

UE data at several Node Bs

• Downlink– Simultaneous transmission

of data via different cells

CNNode B RNC

Node BUE

despreading

despreading

Power control

Transmit Power Control is essential

MS

MS

MS

MS

Near – far problem

Node B

Node B

Transmit Power Control

Minimize the Tx power

Increase the system capacity

More secure detection

How to use the codes

Down Link Up Link

Scrambling Code -To identify cells.-Code shall be assigned to each cell.-Number of Code ; 512-Assignment work by System Designer is required.

-To identify Users.-Code shall be assigned to each user.

-Number of Code ; 224

-Assignment work by System Designer is not required.

Channelization Code

-To identify the channels to be used in a cell.-Code shall be assigned to each user.

-To identify the channels to be used in a user.-Code shall be assigned to each channel.

Summary

34

A case of 3 cell repetitions

Frequency Allocation

f1

f1f1 f1

f1f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1

f1f2 f2

f3f1

f1

f3

f2

f1

f3

f1

f3

f2

f2

f1

f3

f3

f2

f3

f2

FDMA / TDMA CDMA

Same frequency in all cells.

UMTS protocol stacks (user plane)

apps. &protocols

MAC

radio

MAC

radio

RLC SAR

Uu IuCSUE UTRAN 3GMSC

RLC

AAL2

ATM

AAL2

ATM

SAR

apps. &protocols

MAC

radio

MAC

radio

PDCP GTP

Uu IuPSUE UTRAN 3GSGSN

RLC

AAL5

ATM

AAL5

ATM

UDP/IP

PDCP

RLC UDP/IP UDP/IP

Gn

GTP GTP

L2

L1

UDP/IP

L2

L1

GTP

3GGGSN

IP, PPP,…

IP, PPP,…

IP tunnel

Circuitswitched

Packetswitched

36

EDGEEnhanced Data rates for GSM Evolution

• ECSD - Enhanced CSD (Circuit Switched Data)

• EGPRS - Enhanced GPRS

• For higher data rates

• New coding and modulation schemes

• The base stations need to be up dated

• EGPRS up to 384 kbps (48 kbps per time slot)

• ECSD 28.8 kbps

37

Modulation

38

The Beauty ContestTen companies asked for one out of four licences

Licences were given to

• Vodaphone• Tele2• Hi3G• Orange

The incumbent, Telia, was not given a licence!!!

39

UMTS in SwedenThe licensees have to cover 8 860 000 inhabitants.

Two joint ventures:

Svenska UMTS nät - Tele2 and TeliaTelia and Tele2 have established a joint venture, Svenska UMTS nät, with a common 3G network.

3GIS – Telenor and 3*To meet the regulatory requirements, Telenor and 3 has build individualnetworks, and each has to cover 30% of the population. Telenor and 3 have established a joint venture, 3G Infrastructure Services(3GIS) with a common shared network. This network coversapproximately 70% of the population.

Björkdahl & Bohlin

40

Network coverageTheoretically it is possible to cover 8 860 000 inhabitants by covering 20 400 km² of Sweden’s surface area. (Swedish total area is 411 000 km².) Theoretical level corresponds to a coverage of 5% of the Swedish area.

In practice, it seems reasonable that the operators will aim for a total coverage of around 170 000 km². This corresponds to a coverage of 41% of the Swedish surface area.

The operators will be able to cover all urban areas and 84% of the inhabitants by covering around 11 000 km². This corresponds to a coverage of 2.7% of the Swedish surface area.

41

Investment for an average operatorComparing

Germany, United Kingdom and Sweden

The table shows the average 3G investment per capita per year, includingapplicable license fees, in Sweden, Germany and the UK for an average operator in each country, for the entire license duration.

1 USD = 8 SEK

3.8 USD

6.2 USD7.5 USD

42

Summary of main findings

•The average 3G network investment per operator is estimated to be SEK 6.1 billion.

•The total 3G network investment in Sweden is estimated to be SEK 24 billion.

•If the Swedish joint ventures co-operate in rural areas the total 3G network investment is estimated to be SEK 19 billion.

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End of Chapter