UMTSUniversal Mobile

Telecommunication System

Dr. Hatem MOKHTARI

The Hague, 2006

Presentation Outline

Radio Interface

� Multiple access schemes versus CDMA

� W-CDMA technology (Spreading Spectrum)

� Mechanisms to optimize performances

� Limits

� Code planning versus Frequency planning

Multiple Access Schemes

User 1User 2

User 3User 4

User 5

30 KHz

Frequency

Time

Power

FDMA (analog)

A channel is identified by a carrier frequency

TDMA (digital)

Frequency

Time

Power

User 1User 2

User 3User 4

User 1User 2

User 3User 4

200 KHz

A channel is identified by a carrier frequency anda Time Slot assignment.

The channel is the set of TS intervalls usedby the communication

Frequency

Time

Power

FTDMA (GSM) CDMA (IS95, 3G)Power

FrequencyTime

User 1 & 2 & 3 & ...

A channel is identified by a carrier frequency anda code per user

Wideband-Code Division Multiple AccessKey Notions

Wideband-Code Division Multiple Accesstechnology

to provide

Speech, LCD and UDD services

implementing

FDD or TDD modes

On

Physical Channels

Performances

� Soft and softer Handover to improve quality�A mobile is listened by several BTS simultaneously

�User traffic is taken in charge instantaneously by the new BTS (data is then encoded with another code)

� Power Control�Fast power control to optimize capacity (number of users)

� ���� Power ���� ���� Interferences ���� ���� Capacity

� Limits�DL limits: UMTS cell capacity constrained by the number of active users and the maximum power available at the BTS

• Key mechanism to optimize cell capacity = Power control algoritm

�UL limits: trade-off between coverage (cell radius) and guaranteed data service in the cell

– CDMA link budget expertise and receiver performances

• W-CDMA distinguishes usersby codes, the same channelcan be deployed in adjacent cells.� Prefered configuration for

initial deployments• Every UMTS cell site can use

the same 5 MHz band .� N = 1 Reuse

• Channel reuse problemencountered in GSM iseliminated.

• Greatly simplifies frequencyplanning in a fully W-CDMA environment.

1

1

1

1

1

4

1

1

1

1

1

1

1

1

UMTS: N=1 MeansMinimal Frequency

Planning is Required

UMTS: N=1 MeansMinimal Frequency

Planning is Required

4

3

2

7

6

4

CELL1

5

4

3

2

7

6

5

CELL1 GSM N=7

Reuse Pattern

GSM N=7Reuse Pattern

N

orth

ern

Tel

ecom

-C

onfid

entia

lInf

orm

atio

n -

may

not b

eco

pied

or d

iscl

osed

with

outp

erm

issi

onCode Planning (UMTS) Versus Frequency Planning (GSM)

Multiple Access

Multiple AccessSimultaneous Private Use Of An Unique Radio Channel By Multiple Independent Users

Channel #i Channel #i

Channel #i

Channel #i = [FMS(UL), FBTS(DL=UL+duplex spacing)] (Paired Spectrum)OrChannel #i = [FMS(UL), FBTS(= FMS)] (Unpaired Spectrum)

Multiple Access Near Far Problem

• The User 1 is an interferer for the User 2• The User 2 is an interferer for the User 1• The two signals are not synchronised and the codes are

not completely orthogonal���� without power control the base station cannot

discriminate the two signals

Channel #i

Channel #i

User 1

User 2

Multiple AccessIMT-2000 Spectrum

1850 1900 1950 2000 2050 2100 2150 2200 2250

ITU

USA MSSPCS

A D B F D E FBC CAReserveBroadcast auxiliary

2160 MHz1990 MHz

1850 1900 1950 2000 2050 2100 2150 2200 2250

1885 MHz

2025 MHz

2010 MHz

IMT 2000 IMT 2000 MSS

2110 MHz 2170 MHz

Europe

1880 MHz 1980 MHz

GSM 1800 DECT UMTSFDD

MSS UMTSFDD

MSS

1805 MHz

1920 MHz

TDD

MSS

TDD

E

Unpaired Spectrum

Paired Spectrum

Code Division

Cscramb

Code Division User distinguishes By Codes

Channel #i Channel #i

Channel #i

Cscramb : Scrambling Code (distinguishes Cells and Mobile Users)Cch : Channelization Code (distinguishes one Communication Channel direction)

CscrambCch

CscrambCch

CscrambCch

Cscramb

Cscramb

Sector 1

Sector 2

Sector 3

• Uplink: one bit is mapped on the I part of the modulation� SF = Chip Rate/(symbol rate)

Downlink (BS�MS)

Cch,iI

Q

cos (ω t)

sin (ωt)

Channelization Code(OVSF)

* j

p(t)

p(t)

I+jQ

Cscramb

Scrambling Code(Short PN Code)

∑

∑S/PPhysical

Data/ControlChannels

Uplink (MS�BS)

Cch,i

I

Q

cos (ω t)

sin (ωt)

Channelization Code(OVSF)

* j

p(t)

p(t)

I+jQ

Cscramb

Scrambling Code(Long PN Code)

∑

∑

Physical DataChannels

Cch,i

Physical ControlChannel

•Downlink: two bits are transformed into 1 complex symbol� SF = Chip Rate/ (2 symbol rate)

Code DivisionUplink And Downlink Are Different !

� Channelization codes (Orthogonal Variable SpreadingFactor)

�In DL and UL, one Cch assigned by user (handset).

�To spread (Spreading Factor SF) user data rate to the system chip rate.

�To preserve the orthogonality between user ’s differentphysical channels

�OVSF codes defined using a code tree. Where each level in the tree defines a channelization code of length SF.

A code can be assigned if and only if no other code on the pathfrom specific code to the root of the tree or in sub-tree belowthe specific code is already used by an another user.

� Scrambling codes (Gold & Very Large Kasami Codes)

�In DL, one Cscramb assigned by cell (BTS sector).

�In UL, one Cscramb assigned per mobile user.

�To reduce interference between different physical channelsand users.

Code DivisionScrambling And Channelization Codes

TXD(t)

C(t)

αααα D(t-ττττ0).C(t-ττττ0)

ββββ D(t-ττττ1).C(t-ττττ1)

[αD(t-τ0).C(t-τ0)+βD(t-τ1).C(t-τ1)] .C(t-τ0) =α D(t-τ0)

RX

C(t-τ0)

[α D(t-τ0).C(t-τ0)+ β D(t-τ1).C(t-τ1)] .C(t-τ1) =β D(t-τ1)

(αααα +ββββ) D(t)

Code DivisionMultipath RAKE Receiver

ΣΣΣΣRX

C(t-τ1)

Delay(τ1)

RX

C(t-τn)

Delay (τ0)

Delay(τn)

Channelization(OVSF)

Channelization(OVSF)

S/P

2d Interleaving

Physical ChannelMapping

Code DivisionTransmission Chain For One User

SamplingMultipleing data

withsame QoS

Multipleing datawith

different QoS

Physical ChannelSegmentation

2d Interleaving

Physical ChannelMapping

Multipleing datawith

same QoS

Multipleing datawith

same QoS

Channelization(OVSF)

Channelization(OVSF)

S/PScrambling

(Short PN code)

Modulation&

Transmission

PowerAmplification

Channel Coding 1st Interleaving Rate Matching

Channel Coding 1st Interleaving Rate Matching

Channel Coding 1st Interleaving Rate Matching

∑

Baseband Processing

Digital RadioRadio

Voicecalls

Datacalls

Signalling

BitRate

8.8 (voice)64 to 2048 kbps (data)

Chip Rate3.84 Mcps

Symbol Rate64 to 1024 scps

I

Q

Mechanisms To OptimizePerformances

UMTS PerformancesSoft And Softer Handover To Improve Quality

Node B

RNCRNC

Radio SiteRadio Site Radio SiteRadio SiteRadio SiteRadio SiteRadio SiteRadio Site

Node B Node BATMATMConcentratorConcentrator

Soft Handover Soft Handover

Best Frame Selection

Diversity (TX/RX)

Power gain(dB)

Mechanisms to recover transmit data from mobile userMechanisms to recover transmit data from mobile user

Softer Handover Softer Handover

Better EqualizerThroughput

(Bitscombination)

BetterEqualizer

Throughput

UMTS PerformancesPower control

Open Loop Power ControlAccess channel

(the mobile is not connected)

Inner Loop Power Control(radio transmission quality)

Outer Loop Power Control(communication quality target)

RNCRNC

Limits

UMTS PerformancesDownLink Limits

MS2 MS3MS1

BS Power Amplifier

50W

0W

MSi

MS3

y kbps

MS2x kbps

UMTS PerformancesUpLink Limits

Maximum Noise Floor(KTBdB+NFdB)

LowestDespread Signal

Receiver sensitivity (x kbps)

Receiver sensitivity (y kbps)

BS Receiver

ProcessingGain

(y kbps)

ProcessingGain

(x kbps)(x<y)

Eb/No Eb/No

MSix kbps

Cell Breathing

MS1x kbps

UMTS PerformancesLimits

Packet 384 Kbps:

3,5 kmCircuit 384 Kbps:

4,25 km

Speech 8 Kbps(equivalent to Data 20-30 Kbpspossibly more with high-power mobile)

5,5 km

MaximumCoverage

Data Rate (Kbps)

Distance from BTS

Max

Min

Basic Set of Assumptions (ETSI):Tri-Sector Macro-CellOutdoor Vehicular 120 km/h environmentMS-Power: 21 dBm for voice and 27 dBm for DataMS Gain: 2 dB for Data Terminal: Antenna Height: 40 m50% load

UPLINK DOWNLINK

The capacity is tuned by the power control:PBTS= Σ Σ Σ Σ p i

where p i is the power given to user i at time tand PBTS the maximum available power at the BTS

by multipath interferences

Capacity is constrained by the number of active users in a cell and the power allocation policy.

MACRO-CELLVehicular 120 Km/h

UMTS Physical Channels

DS-CDMAFDD

Time

Frequency

Power

Uplink Spectrum Downlink Spectrum1920 MHz 1980 MHz 2110 MHz 2170 MHz

Duplex Spacing : 190MHz

5 MHz 5 MHz

Cch15

UMTS USER 1Cch31

Code MultiplexCch76

Cch15

UMTS USER 2

Time

Frequency

Power

TD-CDMATDD

5 MHz

1900 MHzor

2010 MHz

1920 MHzor

2025 MHz

DL

Cch25

UL

DL

Cch91

UMTS USER 2

Code Multiplex&

Time DivisionDL

Cch38

625 µµµµsUMTS USER 1

UL

Cch61

UMTS Physical ChannelsFDD And TDD Channel

Services

ServicesLCD And UDD Services For FDD Bearers

W-CDMAFDD

Time

Frequency

Power

UL DL

LCD: Long Constrained DelayCircuit connection emulation (for Speech service also)Code(s) allocated to the unique use of one user communicationFixed services: LCD64, LCD144, LCD384 and LCD2048

User 1LCD service

C11C25

C15

User 3UDD service

C100C74

User 2UDD service

C32

C100

UDD: Unconstrained Delay DataPacket connection (shared codes as GPRS has shared channels)Code(s) can be re-allocated to an another user during a communicationFlexible data services (UDD64, UDD144, UDD384 and UDD2048 exist)

Spreading Spectrum

Spreading SpectrumNotion

User 1Symbol Rate (ksps)

3.84 Mcps

FixedChip Rate (kcps)

Code 1 (Ksps)

Code 2 (length < code 1 length)

Chip rate = Symbol rate * SFChip rate = Symbol rate * SF

SpreadingFactor(SF)

User 2Symbol Rate (ksps) (>User 1)

Spreading SpectrumPrinciple And Advantage (DS-CDMA)

W-CDMA

X Code (OVSF)

5 MHz

270 Kbit

GSM

200 KHz

BurstedMode

ProcessingGain

CWMode

3.84 Mcps

Spreading SpectrumProperties

WBNBThe processing gain = WB/NB

• A Narrow Band signal spreadwith a code is a spread signal.• A spread signal is despreadwith the same spreading code.

OVSF code

OVSF code• A spread signal despreadwith the wrong coderemains spread

OVSF code• Narrow Band signaldespread is a spread signal

(1,-1,1,-1)

SPREADING SPECTRUMCode Tree For Channelization Codes (OVSF)

SF = 64SF = 32SF = 16SF = 4SF = 2SF = 1 SF = 256SF = 128

(1,1,1,1)

(1,1,-1,-1)

(1,-1,-1,1)

No Spreading Factor

Unusable

Unusable

Unusable

(1)

(1,1)

(1,-1)

32

SF=4 SF=8 SF=16

UDD384

LCD384

UDD384

LCD384

LCD144LCD64

LCD144

UDD144

LCD64

LCD144

UDD144

LCD64

UDD64

UDD144

LCD64

UDD64

UDD144

LCD64

UDD64

UDD144

LCD64

UDD64

UDD144

SF=32 SF=64

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

Speech

SF=128 SF=256

UDD64

UDD64

UDD64

UDD64

UDD64

UDD64

UDD64

UDD64

Spreading SpectrumMapping Of Bearers On Physical Channels

Spreading OVSF (Example)

Spreading OVSFTransmited Signal

-11USER 1

USER 2

Code Cch1 (SF=16)

Code Cch2 (SF=4)

TransmittedSignal(fixed Chip Rate)

1-11 1-11

Spreading OVSFData Extraction (Reception)

« 1 »« 0 »« 1 »

ReceivedSignal

USER 2

Code Cch2 (SF=4)

Soft Bits2 2

+= 4

0 0 -2 -2 0 0 2 2 0 0 0 0 2 2 -2 -2 0 0 2 2 0 0

= -4+

= 4+

= 4+

= 4= -4

« 1 » « 1 »« 0 »

Spreading OVSFOrthogonality

+No correlation between codes.

Cj presence does not affect Ck energy.If To not respected then no orthogonality ==> Interference

No correlation between codes.Cj presence does not affect Ck energy.

If To not respected then no orthogonality ==> Interference

-1 -1 -1

-1 -1 -1 -1

1 1 1 1

1 1 1 1

-1

*

1 1 1 1-1 -1 -1 -1 = 0

Cj

Ck

To (synchronisation)

Network Interfaces

PHY PHY

ATM

AAL5

PHY

ATM

AAL5

MAC

PHY

MAC

MACRLCMACRLC

Non Access Stratum(OSI 4-7)

Access Stratum(OSI 1-3)

Core NetworkRadio Access NetworkUser Equipment

RRC RRCMTP 3

SCCP

RANAP

MTP 3

SCCP

RANAP

Gc Nt Dc Gc Nt Dc

MM

CM

MM

CM

User Data User Data

Uu interface Iu interface

Control Plane

User Plane

Transport Network User Plane

ATM ATM

AAL 2 AAL 2

Network InterfacesNon Access Stratum User and Control Planes

RNC

RNC

RAN

Network InterfacesIu

Iu:

CSDomain

PSDomain

Internet

or Intranets

U-SGSN

Mobility Management

Session Management

= Bearer Path (User-Plane or U-Plane)= Transport Layer Signalling Path (Control-Plane or C-Plane)= Radio Network Layer Signalling Path

ATMAAL5

SAAL-NNIMTP3bSCCP

RANAP

DM

TA

P

MM

-CS

ATMAAL5

SAAL-NNIMTP3b

Q.2630.1

ATMAAL2

UMTS AMRVoice

Transcoding

Mobility Management

Call Control

PSTN Interworking

U-MSC

ATMAAL5

SAAL-NNIMTP3bSCCP

RANAPS

M

MM

-PS

ATMAAL5

IPSIGTRAN

SCCP

RANAP

SM

MM

-PS

Standards allow either stack – at least for now.

ATMAAL5

IPUDPGTP

Payload (IP)

Any L1Any L2

IPUDPGTP

IPGn C-Plane

GGSN

IP

�

PCMPSTNs/ISDNs

RNC

Network InterfacesUu

CommonpCH

SharedpCH

DedicatedpCH

ODMApCH

Channel coding

CommonCH

SharedCH

DedicatedCH

ODMACH

MAC (Medium Access Control)

CommonpCH

Dedicated ControlChannel

CommonChannel

Dedicated TrafficChannel

RLC (Radio Link Control)

RRC (Radio Resource Control)

AM UM TR

Gc Nt Dc

RLC

AM UM TR

Non Access StratumNon Access StratumNon Access Stratum

Access StratumAccess StratumAccess Stratum

Logical Channels SAP(Service Access Point)

Logical Channels

Transport Channels

Physical Data Channels

Control Plane User Plane

L1L1L1

L2L2L2

L3L3L3

Spreading&

Modulation

Physical ControlChannel

Physical Channels

Slot #2Slot #1 Slot #j Slot #16

10 ms Frame = 16 slots = 40960 chips

Frame #1Frame #0 Frame #i Frame #71

720 ms Super Frame =72 frames*10ms

1 slot = 0,625 ms

Physical ChannelsFDD & TDD Frame Structure

3.84 Mcps Chip Rate decreasesthe number of slots down to 15

3.84 Mcps Chip Rate decreasesthe number of slots down to 15

10 ms Frame = 16 slots = 40960 chips

Slot #2Slot #1 Slot #j Slot #16

1 slot = 0,625 ms = 2560 I&Q chips (downlink)

Secondary CCpCH FACH or PCH Data Pilot

Secondary CCpdCH (2304 chips)Secondary CCpcCH

(256 chips)

Primary SpcCH

(slot sync)

Secondary SpcCH

(frame sync)

Primary CCpCHPrimary CCpdCH

(BCH Data)

Primary CCpcCH

(Pilot)

Primary CCpdCH (1280 chips) Primary CCpcCH (1024 chips)

Sync pCH

(256 chips)

Physical ChannelsCommon Control pCHs (FDD)

RACH Message Part(RApdCH+RApcCH)I+Q

RACH preamble(RApcCH)I&Q

RACH preamble(RApcCH)I&Q

AICH answer(AIpcCH)I&Q

Sig

natu

re i

Sig

natu

re i

Sig

natu

re i

Data (Ndata bits)

pilotRate Information

Uplink(UE)

Downlink(Cell)

I

Q

1 ms

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 161 2 3 4 5 6 7 8 9 10 11 12 13 14 15 161 2 3 4 5 6 7 8 9 10 11 12 13 14 15 161 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

10 ms

1.25 ms

Physical ChannelsRandom Access pCHs (FDD)

UplinkI+Q

Downlink I&Q

DpdCHDpcCH DpdCH DpcCH DpcCH

10 ms Frame = 16 slots = 40960 chips

Slot #2Slot #1 Slot #j Slot #16

1 slot = 0,625 msNbits=>Nsymbols*SF = 2560 chips

TFCI=Ntfci bits

Data1Ndata1bits

TPCNtpc bits

Data2Ndata2bits

PilotNpilot bits

DataNdatabits

TFCI=Ntfci bits

TPCNtpc bits

PilotNpilot bits

FBINfbi bits

DpdCH

DpcCH

Physical ChannelsDedicated pCHs (FDD)

10 ms Frame = 16 slots = 40960 chips

1 slot = 0,625 ms = 2560 chips

RACHSCH SCH

BCH BCH

FACH FACH

PCH PCH

8-10 users per slot in downlink(Code Division)

RACH

RACH

RACH

Up to 16 simultaneous RACH(Code Division+Time Division)

DCH1

DCH2

DCH3

DCH4 DCH1

DCH2

DCH3

DCH4

Up to 8 users per slot in uplink(Code Division)

Slot type(Time Division)

Channel assignment

(Code Division)

Common Control

TS#0

uuuu

RandomAccess

TS#8

tttt

Common Control

TS#7

uuuu

DedicatedpCHTS#1

uuuu

DedicatedpCHTS#6

uuuu

DedicatedpCHTS#9

tttt

DedicatedpCHTS#15

tttt

... ...

Physical ChannelsTDD Frame example

10 ms Frame = 16 slots = 40960 chips

Slot #1Slot #0 Slot #i Slot #15

1/2 slot =0,3125ms= 1280 I&Q chips (uplink)

Access Burst 2 RACH DataGuard

period96 chips

Midamble512 chips

Data Symbols (336 chips) (512 chips)(512 chips)

RACH Data

Data Symbols (336 chips)

Extended

Guard period1280 chips

Access Burst 1 RACH DataGuard

period96 chips

Midamble512 chips

Data Symbols (336 chips) (512 chips)(512 chips)

RACH Data

Data Symbols (336 chips)

Extended

Guard period1280 chips

1/2 slot =0,3125ms= 1280 I&Q chips (uplink)

Physical ChannelsRandom Access pCHs (TDD)

10 ms Frame = 16 slots = 40960 chips

Slot #1Slot #0 Slot #8 Slot #15

1 slot = 0,625 ms = 2560 I&Q chips (downlink)

CCpCH(over burst 2)

Primary SpcCH

(slot sync)

Secondary SpcCH

(frame sync)

CCpCH(over burst 1)

BCH/FACH/PCH DataGuard

period96 chips

Data Symbols (976 chips)

Sync pCH

(256 chips) (256 chips)

Toffset Tgap

BCH/FACH/PCH DataMidamble512 chips

Data Symbols (976 chips)

BCH/FACH/PACH DataBCH/FACH/PACH DataGuard Guard

periodperiod96 chips96 chips

BCH/FACH/PCH DataBCH/FACH/PCH DataMidambleMidamble256 chips256 chips

Data Symbols (1104 chips)Data Symbols (1104 chips)Data Symbols (1104 chips)Data Symbols (1104 chips)

(512 chips)(512 chips)

(256 chips)(256 chips)

Physical ChannelsCommon Control pCHs (TDD)

1 slot = 0,625 ms = 2560 I&Q chips

Burst type 2 Data symbols*SFData symbols*SF1104 chips1104 chips

Data Symbols*SFData Symbols*SF1104 chips1104 chips

MidambleMidamble256 chips256 chips

Guard

period

96

chips

Burst type 1Data symbols*SF

976 chipsData Symbols*SF

976 chips

Midamble512 chips

Guard

period

96

chips

1/2 Burst (pos 1 &2)

Data*SF

336 chips

Guard

period

96 chips

Midamble512 chips

Data*SF

336 chips

Data*SF

336 chips

Guard

period

96 chips

Midamble512 chips

Data*SF

336 chips

1/2 slot = 0,315 ms = 1280 I&Q chips

Physical ChannelsBurst structure (TDD)