42164892 Intoduction WCDMA Fundamantels[1]

MobileComm Technologies India Pvt. Ltd.

Dallas . Atlanta . Washington . LA . Sao Paulo . New Delhi . Toronto . Muscat. Sydney

Introduction & WCDMA Fundamentals

Copyright 2010 MobileComm Technologies India Pvt. Ltd.

All rights reserved

MobileComm is committed to providing our customers with quality instructor led

Telecommunications Training.

This documentation is protected by copyright. No part of the contents of this

documentation may be reproduced in any form, or by any means, without the prior written consent of MobileComm Technologies .

Document Number: RK/CT/3/2010

This manual prepared by: MobileComm Technologies

MobileComm Technologies(India)Pvt. Ltd.424, First Floor, Udyog Vihar Phase -4,

Gurgaon-122002

Headquarter:MobileComm Professionals Inc.1255 West 15th Street, Suite 440

Plano, TX, 75075Tel: (972) 633-5100Fax: (972) 633-5106www.mcpsinc.com

http://www.mcpsinc.com/

• Understand why 3G was created

• Different services in 3G

• How QoS is ensured by 3G

Objectives

At the end of this session, you will be able to:

Introduction

Mobile Network Evolution

1G

Analogue

2G

Digital

2.5G

Packet Data

2.75G

Enhanced Data

NMT

TACS

AMPS

GSM

CDMA

TDMA

GPRS

EDGE

CDMA 1X

WCDMA

TD-SCDMA

cdma2000

1X EV-DO

2M, 14M

2M

2.4M

384K

144K

1982-1996+ 1992-2002+ 2001+ 2004+ 2002-2004+

115K

A Third Generation of Mobile Systems: What for?

• Concepts of 3G - Mobiles

Voice & Music phone

Mobile Audio Video

Communicator

PC / PDA PCMCIA card

A Third Generation of Mobile Systems: What for?

Standardization Bodies

T1 ETSI TTC / ARIB TTA CWTS TIA

= 3GPP2

Standardisation of 3G cellular networks

– ITU (Global guidelines and recommendations)

• IMT-2000: Global standard for third generation (3G) wireless communications

– 3GPP is a co-operation between standardisation bodiesETSI (Europe), ARIB/TTC (Japan), CCSA (China), ATIS (North America) and TTA (South Korea)

• GSM

– EDGE

• UMTS

– WCDMA - FDD

– WCDMA - TDD

• TD-SCDMA

– 3GPP2 is a co-operation between standardisation bodiesARIB/TTC (Japan), CCSA (China), TIA (North America) and TTA (South Korea)

• CDMA2000

– CDMA2000 1x

– CDMA2000 1xEV-DO

2 Mbit/s 384 kbit/s 144 kbit/s

Indoor

low mobility

Urban

reduced mobility

Rural outdoor

high mobility

• Variable bit rate capability

• Variable Quality Of Service (BER, delay)

• Support of asymmetric traffic

• Service multiplexing

• High spectrum efficiency

• European objective: ensure compatibility with GSM

3GPP Objectives

Added Value of UMTS

Mobile Networks and Data Services

2G Mobile

3G (UMTS)

3.5G or 3G+ (HSDPA and HSUPA)

2.5G (GPRS)

2.75G (EDGE)

3G Mobile

LTE

WiMAX

HSDPA

UMTS

EDGE

GPRS 160kbps

384Kbps

2Mbps *

14.4Mbps *

75Mbps *

100Mbps ? *

* : Per cell bandwidth (not per user)WiMAX ("3G" or "4G" depending on manufacturer)

Future: 4G (LTE)

HSUPA 5.7Mbps *

Maximum Theoretical Bandwidth

UMTS QoS class

NRT Data Call

Background Class

PS Data Call

Interactive Class

PS Data Call

Streaming Class

PS Data Call

Conversational Class

CS Data Call

CS Data Call CS Voice Call

CS Call

RT Data Call

PS Call

Call

Why do we need QoS?

• UMTS networks support services with very different performance requirements

– Real-time services require performance guarantees

– Customer acceptance closely tied to service quality

• Optimal usage of network resources

– Radio resources scarce

– Cost-effectiveness

– Return of investment

• Service and user differentiation

– Meet different needs of customers (e.g. business vs. consumer)

– Support different services (real-time vs. best effort)

• Competitive advantage! Delay Jitter Loss

Video call High High High Med

Streaming High Med Med Med

Web browsing Med Med Low High

E-mail Low Low Low High

Application BandwidthSensitivity

Performance Requirements

QoS Traffic Classes

QoS Traffic Classes

Traffic class Characteristics Example

application

Conversational Preserve time relation between

information entities of the stream.

Conversational pattern (stringent and

low delay)

Speech

Video calls

Streaming Preserve time relation between

information entities of the stream.

Real-time

streaming

video

Interactive Request-response pattern. Preserve

payload content.

Web browsing

Background Destination is not expecting the data

within a certain time. Preserve

payload content.

E-mail

File

downloading

Demanding

• Delay

• Jitter

Demanding

• Bit rate

• Jitter

Tolerant

• Delay and bit rate can vary

• Integrity

Easiest

• Delay and bit ratecan vary

• Integrity

QoS for different services

UMTS BEARERS

The Attributes (QoS Parameters) of a Bearer Service can be negotiated at the beginning of connection and during a connection Several different Bearer Services can be established simultaneously by one UE

Important Quality Parameters are– Maximum transfer delay – Delay variation – Bit error ratio– Data rate

“A bearer is a logical connection between two end points with specific service

capabilities”

A bearer service includes all aspects to enable the provision of a contracted QoS (e.g.,

controlling, signalling, user plane transport, management functionalities).

“QoS support in UMTS is based on the concept of bearer service”

UMTS BEARERS : Example

RAB Class Usage

AMR 12.2 Conversational Voice

CS C 64 Conversational Video conferencing

PS I/B 8/8 Interactive / Background Email/Internet




PS I/B 64/384 Streaming Live Audio/Video

PS I/B 128/128 Streaming Live Audio/Video

QoS Differentiation

Conversational RAB

Streaming RAB

Interactive RAB

Interactive RAB

Background RAB

MMS

Web

browsing

Push-to-talk

Streaming

Video

telephony

• Each service gets the treatment it requires according to the QoS profile

• Network resources are shared according to the service needs

• Network resources can be used more efficiently

WCDMA Network Structure

GSM /GPRS BSS

BTS

BSC

PCUSS7

SCP

SMS

SCE

PSTN/other PLMN

Internet,

Intranet

MSC/VLR GMSC

HLR/AUC

SGSN

CG BG

GGSN

PS backbone

Other PLMN

CS domain

PS domain

NodeB

RNC

UTRAN

Iu-CS

Iu-PS

A

Gb

GERAN

WCDMA Interfaces

A Interface

A-bis

Um

MSC

BSC

BTS

UE

SGSN

Gb

GSM

Iub

Uu

MSC

RNC

NodeB

UE

SGSN

Iu-PSIu-CS

Iub

Uu

RNC

NodeB

UE

Iur

WCDMA

UTRANBSS

GERAN

Radio Network Interfaces

• Iu

– Iu PS

• Connection to the packet switched core network domain

– SGSN/GGSN

– Iu CS

• Connection to the circuit switched core network domain

– MSC

– Protocol RANAP

• Iur

– RNC interconnection [eg: for SHO support ]

– Protocol RNSAP

• Iub

– Connection for the RBS to the RNC

– Protocol NBAP

• Uu

– Air Interface to the UE

– Protocol RRC, RLC, MAC

Core Network

RNC

RNC

Iu

Iur

Iub

UuNode

B

NodeB

NodeB

UE

•WCDMA Air Interface

•WCDMA Principles & Spreading codes

•Overview of Radio Resource Management (RRM)

•Load control

•Admission Control

•Packet Scheduler

•Resource Manager

•Power Control

•Handover Control

•Capacity limitation and Cell breathing

•Rake receiver

Objectives

At the end of this session, you will be able to:

W-CDMA Fundamantels

Agenda



• Overview of Radio Resource Management (RRM)


•Rake receiver

Power

PowerPower

FDMA TDMA

W-CDMA

Access Technologies

What do YOU hear...

•If you only speak Japanese?

•If you only speak English?

•If you only speak Italian?

•If you only speak Japanese, but the Japanese-speaking person is all the way across the room?

•If you only speak Russian, but the Spanish-speaking person is talking very loudly?

WCDMA Cocktail Party

UMTS Air Interface technologies

– UMTS Air interface is built based on two technological solutions• WCDMA – FDD• WCDMA – TDD

– WCDMA – FDD is the more widely used solution• FDD: Separate UL and DL frequency band

– WCDMA – TDD technology is currently used in limited number of networks

• TDD: UL and DL separated by time, utilizing same frequency

– Both technologies have own dedicated frequency bands

– This course concentrates on design principles of WCDMA – FDD solution, basic planning principles apply to both technologies

Duplex Spacing: 190 MHz

FDD

Time

Frequency

Power

5 MHz 5 MHz

Code Multiplex

UL DL

UMTS USER 1

UMTS USER 2

Time

Frequency

Power

TDD

5 MHz

Code Multiplex

&

Time Division

666.67 ms

DL

UL

DL

DL

UL

UMTS USER 2

UMTS USER 1

• W-CDMA: FDD or TDD


• W-CDMA FDD mode for the paired band

– uplink and downlink are separated in frequency

TD-CDMA TDD mode for the unpaired band

– uplink and downlink are separated in time

– flexible time duration for uplink and downlink for asymmetrical traffic


WCDMA Technology

5 MHz

3.84 MHz

f

5+5 MHz in FDD mode5 MHz in TDD mode

Fre

qu

ency

TimeDirect Sequence (DS) CDMA

WCDMA Carrier

WCDMA5 MHz, 1 carrier

TDMA (GSM)5 MHz, 25 carriers

Users share same time and frequency

IMT-2000 frequency allocations

2200 MHz20001900 1950 2050 2100 21501850

JapanIMT-2000

PH

S IMT-2000

ITU

Mo

bil

e

Sate

llit

e

IMT-2000 IMT-2000

EuropeUMTS(FDD)

DE

CT

UM

TS

(T

DD

)

GSM1800

UM

TS

(T

DD

)

UMTS(FDD)

USA

PC

S

un

lic

en

se

d

PCSPCS

UM

TS

(T

DD

)IM

T-2

000 (

TD

D)

Mo

bil

e

Sate

llit

eM

ob

ile

Sate

llit

e

Mo

bil

e

Sate

llit

eM

ob

ile

Sate

llit

e

Mo

bil

e

Sate

llit

e

Mo

bil

e

Sate

llit

e

Mo

bil

e

Sate

llit

e

ITU-R

•responsible for world-wide Radio Communication aspects

• setting requirements for 3G / 4G Mobile Communication (IMT-2000 / IMT-Advanced)

•World Radio ConferenceWRC 1992: IMT-2000 frequency allocation proposals

national regulation authorities:

• responsible for national frequency allocation & licensing process

•GSM spectrum refarming is also possible

UMTS – FDD Frequency band evolution

– Release 99• I 1920 – 1980 MHz 2110 –2170 MHz UMTS only in Europe, Japan, India• II 1850 –1910 MHz 1930 –1990 MHz US PCS, GSM1900

– New in Release 5• III 1710-1785 MHz 1805-1880 MHz GSM1800

– New in Release 6• IV 1710-1755 MHz 2110-2155 MHz US 2.1 GHz band• V 824-849MHz 869-894MHz US cellular, GSM850• VI 830-840 MHz 875-885 MHz Japan

– New in Release 7• VII 2500-2570 MHz 2620-2690 MHz• VIII 880-915 MHz 925-960 MHz GSM900• IX 1749.9-1784.9 MHz 1844.9-1879.9 MHz Japan

UMTS-2100 Uplink Downlink

1980 MHz1920 MHz 2110 MHz 2170 MHz

UMTS frequency allocations

Duplex Frequency : 2110-1920 = 190 MHz

Bandwidth :1980-1920 = 60 MHz

Carriers : 60 / 5 = 12

UL : 1959 MHz – 1979 MHz

DL : 2149 MHz – 2169 MHz

Frequency channel numbering

UTRA Absolute Radio Frequency Channel Number (UARFCN)

UARFCN formula (3GPP 25.101 and 25.104):

UARFCN = 5 . f [MHz]Uplink/Downlink Center Uplink/Downlink

with

0.0 MHz <= fCenter Uplink/Downlink

UARFCN is integer:

0 <= UARFCN <= 16383

<=3276.6 [MHz]

Center Frequency

Center Frequency fcenter

Consequence of UARFCN formula (see previous slide):

• fcenter must be set in steps of 0.2MHz (Channel Raster=200 kHz)

• fcenter must terminate with an even number (e.g 1927.4 not 1927.5)

fcenter values

Uplink (1920Mhz-1980MHz)

1922.4MHz <= fcenter <= 1977.6MHz

9612 <= UARFCN Uplink <= 9888

Downlink (2110Mhz-2170MHz)

2112.4MHz <= fcenter <= 2167.6MHz

10562 <= UARFCN Downlink <= 10838

WCDMA – FDD technology

– Multiple access technology is wideband CDMA (WCDMA)• All cells at same carrier frequency• Spreading codes used to separate cells and users• Signal bandwidth 3.84 MHz

– Multiple carriers can be used to increase capacity• Inter-Frequency functionality to support mobility between

frequencies

– Compatibility with GSM technology• Inter-System functionality to support mobility between GSM and

UMTS

UMTS & GSM Network Planning

GSM900/1800: 3G (WCDMA):

Differences between WCDMA & GSM

WCDMA GSM

Carrier spacing 5 MHz 200 kHz

Frequency reuse factor 1 1–18

Power controlfrequency

1500 Hz 2 Hz or lower

Quality control Radio resourcemanagement algorithms

Network planning(frequency planning)

Frequency diversity 5 MHz bandwidth givesmultipath diversity with

Rake receiver

Frequency hopping

Packet data Load-based packetscheduling

Timeslot basedscheduling with GPRS

Downlink transmitdiversity

Supported forimproving downlink

capacity

Not supported by thestandard, but can be

applied

High bit rates

Services withDifferent quality

requirements

Efficient packet data

Agenda



•Channelization Code

•Scrambling Code



•Rake receiver

WCDMA Features

• Separate users through different codes

• Large bandwidth

• Continuous transmission and reception

• Code planning - Frequency reuse is 1

• No frequency planning

• Scrambling code planning

• 5 MHz carrier separation

• Fast Power Control

• Soft/Softer Handover

• Admission Control

• Congestion Controlfrequency

Code-Division Multiple Access

codeCDMA

3GPP : 3rd Generation Partnership Projecthttp://www.3gpp.org

• Separates users through different codes

• Codes are used for two purposes:

• Differentiate channels/users

• Spreading the data over the entire bandwidth

f

Code

t

MS 1MS 2MS 3

5 MHz

• WCDMA (5 MHz)

• IS-95 (1.25 MHz)

• CDMA2000 (1.25, 3.75 MHz)

Spreading Principle

Direct Sequence Spreading - Code Division Multiple Access (DS-CDMA)

Spreading Principle

Spreading code = Scrambling code + Channelization code

• Scrambling codes (Repeat period 10 ms=38400 chips)– Separates different mobiles (in uplink)

– Separates different cells (in downlink)

• Channelization codes– Separates different channels that are transmitted on the same scrambling code

– Orthogonal Variable Spreading Factor (OVSF) codes

– Period depends on data rate

Spreading Code

Spread Signal

Data

Air Interface

Bits (In this drawing, 1 bit = 8 Chips SF=8)

Baseband Data

-1

+1

+1

+1

+1

+1

-1

-1

-1

-1

ChipChip

CDMA principle - Chips & Bits & Symbols

Common Technical Terms

Bit, Symbol, Chip:

A bit is the input data which contain information

A symbol is the output of the convolution, encoder, and the block interleaving

A chip is the output of spreading

Processing Gain:

Processing gain is the ratio of chip rate to the bit rate.

Closely related to spreading factor, SF.

Forward direction/ Downlink : Information path from base station to mobile station

Reverse direction/ Uplink : Information path from mobile station to base station

Block Diagram of WCDMA System

Source coding Channel

codingSpreading Modulation

Source

decoding

Channel

decodingDespreading Demodulation

Radio channel

WCDMA System

Source Coding

Voice : Adaptive multirate technique with rate 4.75kbps – 12.2kbps

Channel Coding

CRC Attachment.

Check for error during transmission.

Voice : CRC check returns error, discard information

Data : CRC check returns error; ask for retransmission

Convolutional or Turbo Coding

Convolution coding for voice and low speed signaling

Turbo Coding for large data transmission. Better performance than convolutional coding

Interleaving

Distribute error over data transmitted

Rate Matching

Match symbol rate to that accepted by spreading

Rate matching technique : Repeat or puncturing

Spreading Principle

User information bits are spread into a number of chips by multiplying them with a spreading code

The chip rate for the system is 3.84 Mchip/s and the signal is spread in 5 MHz

The Spreading Factor (SF) is the ratio between the chip rate and the symbol rate

The same code is used for de/spreading the information after it is sent over the air interface.

Information signal

Spreading signal

Transmission signal

Spreading Technology

Spreading consists of 2 steps： Channelization operation: Transforms data symbols into chips. Thus

increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor（SF）.The operation is done through multiplication with OVSF code.

Scrambling operation is applied to the spreading signal.

Data bit

OVSF code

Scrambling code

Chips after spreading

DL & UL Channelisation Codes

– Walsh-Hadamard codes: orthogonal variable spreading factor codes (OVSF codes)

• SF for the DL transmission in FDD mode = {4, 8, 16, 32, 64, 128, 256, 512}

• SF for the UL transmission in FDD mode = {4, 8, 16, 32, 64, 128, 256}

– Good orthogonality properties: cross correlation value for each code pair in the code set equals 0

• In theoretical environment users of one cell do not interfere each other in DL

• In practical multipath environment orthogonality is partly lost Interference between users of same cell

– Orthogonal codes are suited for channel separation, where synchronisation between different channels can be guaranteed

• Downlink channels under one cell

• Uplink channels from a single user

– Orthogonal codes have bad auto correlation properties and thus not suited in an asynchronous environment

• Scrambling code required to separate signals between cells in DL and users in UL

Channelisation Code Tree

C0(0)=[1]

C2(1)=[1-1]

C2(0)=[11]

C4(0)=[1111]

C4(1)=[11-1-1]

C4(2)=[1-11-1]

C4(3)=[1-1-11]

C8(0)=[11111111]

C8(1)=[1111-1-1-1-1]

C8(2)=[11-1-111-1-1]

C8(3)=[11-1-1-1-111]

C8(0)=[1-11-11-11-1]

C8(5)=[1-11-1-11-11]

C8(6)=[1-1-111-1-11]

C8(7)=[1-1-11-111-1]

C16(0)=[............]

C16(1)=[............]

C16(15)=[...........]

C16(14)=[...........]

C16(13=[...........]

C16(12)=[...........]

C16(11)=[...........]

C16(10)=[...........]

C16(9)=[............]

C16(8)=[............]

C16(7)=[............]

C16(6)=[............]

C16(5)=[............]

C16(4)=[............]

C16(3)=[............]

C16(2)=[............]

SF=1 SF=2 SF=4 SF=8 SF=16 SF=256 SF=512...

SF and Service Rate

Symbol Rate*SF=Chip Rate

In WCDMA system, if chip rate=3.84MHz, SF=4, then symbol rate=960Kbps.

Symbol Rate=(Service Rate + Checking Code)*Channel Coding Rate* Repeat or Puncture Rate

In WCDMA system, if service rate=384Kbps, channel coding=1/3 Turbo coding, then symbol rate=960Kbps;

Correlation Function

Input Data +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 +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

Channelization code

in Transmitter

Transmitted

Sequence

Channelization Code

used in Receiver

8 0 - 4

Integrate

Result

+1 0 - 0.5Divide by

Code Length

Correlation using channelization codes

(a) Same channelization code; (b) Different channelization codes ; (c) Same code with non zero time offset

x x x

Integrate Integrate Integrate

= = =

x x x

= = =

Transmitter

Receiver

Input Data +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 +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

Channelization code

in Transmitter

Transmitted

Sequence

Channelization Code

used in Receiver

8 0 - 4

Integrate

Result

+1 0 - 0.5Divide by

Code Length

-

x x x

Integrate Integrate Integrate

= = =

x x x

= = =

Transmitter

Receiver

Desp

read

ing

User

data

Spreading code

Chip

sequence

0 1

1 1 0 0 1 1 0 0

+1

0

-1

+1

0

-1

+1

0

-1

Spreading

1 1 0 0 1 1 0 0

+1

0

-1

+1

0

-1

+1

0

-1

Case 1

1 0 1 0 1 0 1 0

+1

0

-1

+1

0

-1

+1

0

-1

Case 2

Spreading Principle

Spread Spectrum Gain

Benefits of Spreading

MOD DEM DETF

MOD - modulation

DEM - demodulation

F - filtering

DET - detection

NBI - narrow-band interference

WBI - wide-band interference

384 kbps

1

1

f

P

Spreading code3.84 Mcps

2

Spreading factor

Processing gain

G =Rchip

Rbit

f

P

2

WBI

NBI3

f

P

WBI

NBI 3

4

P

f

4

5

f

P

5

Frequency (Hz)

Voice user (R=12,2 kbit/s)

Packet data user (R=384 kbit/s)

Po

wer

den

sit

y (

W/H

z)

R

Frequency (Hz)

Gp=W/R=24.98dB

Po

wer

den

sit

y (

W/H

z)

R

Gp=W/R=10 dB

• Spreading sequences have a different length

• Processing gain depends on the user

data rate

Processing Gain Examples

R

WdBGp Processing gain:

•The more processing gain the system has, the more the power of uncorrelated interfering signals is suppressed in the despreading process.

•Thus, processing gain can be seen as an improvement factor in the SIR (Signal to Interference Ratio) of the signal after despreading.

Example: Voice AMR 12.2 Kbps

Gp= 10*log(3840000/12200)= 25 dB.

•After despreading the signal power has to be typically few dB above the interference and noise: Eb/No = 5dB; therefore the required wideband signal-to-interference ratio is 5dB –Gp= -20 dB.

•In other words, the signal power can be 20 dB under the interference and the WCDMA receiver can still detect the signal.

Processing gain

Energy Box

Duration (t = 1/Rb)

Originating Bit Received Bit

Energy per bit = Eb = const

• Higher spreading factor Wider frequency band Lower power spectral density

• BUT

• Same Energy per Bit

Transmission Power

Frequency

5MHz

Power density

Time

High bit rate user

Low bit rate user

Correlation between: Capacity, Interference, Load & Power

Channelization Codes

CC1, CC2CC3, CC4

CC5, CC6, CC7

CC1 , CC2, CC3CC1, CC2

CC1, CC2, CC3, CC4

In the Uplink, Channelization Codes are used to distinguish between data (and control) channels from the same UE

In the Downlink, Channelization Codes are used to distinguish between data (and control) channels coming from the same NodeB

Channelization Codes have different length depending on the bit rate

After the Channelization Codes, the data stream is multiplied by a special code to distinguish between different transmitters.

Scrambling codes are not orthogonal so they do not need to be synchronized

The separation of scrambling codes is proportional to the code length – longer codes, better separation (but not 100%)

Scrambling codes are 38400 chips long

Scrambling Codes

Scrambling Codes

SC3 SC4

SC5 SC6

SC1 SC1

Cell “1” transmits using SC1

SC2 SC2

Cell “2” transmits using SC2

In the Downlink, the Scrambling Codes are used to distinguish each cell (assigned by operator – SC planning)

In the Uplink, the Scrambling Codes are used to distinguish each UE (assigned by network)

Scrambling Code planning example

SC 0

SC 16 SC 40

SC 32

SC 56

SC 24 SC 1

SC 17 SC 41

SC 33

SC 64

SC 8

SC 48

SC 9 SC 25

SC 57

SC 65

SC 49

Spreading factor

Channel symbol

rate

(ksps)

Channel bit rate

(kbps)

DPDCH channel bit rate range

(kbps)

Maximum user data rate with ½-

rate coding

(approx.)

512 7.5 15 3–6 1–3 kbps

256 15 30 12–24 6–12 kbps

128 30 60 42–51 20–24 kbps

64 60 120 90 45 kbps

32 120 240 210 105 kbps

16 240 480 432 215 kbps

8 480 960 912 456 kbps

4 960 1920 1872 936 kbps

4, with 3 parallel codes

2880 5760 5616 2.3 Mbps

Half rate speech

Full rate speech

128 kbps

384 kbps

2 Mbps

Symbolphyb RR 2_SF

WRSymbol

(QPSK modulation)

Physical Layer Bit Rates (DL)

Modulation :

DL : QPSK, 16 QAM.

UL : BPSK

DL & UL Scrambling Codes

DL Scrambling Codes

– Pseudo noise codes used for cell separation

• 512 Primary Scrambling Codes

UL Scrambling Codes

– Two different types of UL scrambling codes are generated

• Long scrambling codes of length of 38 400 chips = 10 ms radio frame

• Short scrambling codes of length of 256 chips are periodically repeated to get the scrambling code of the frame length

– Short codes enable advanced receiver structures in future

•512 DL Primary Scrambling Codes•16.7 million UL Scrambling Codes

Basic W-CDMA Terminologies

Eb/No

C

I

N

C

CEb/No

W-CDMATDMA-GSM

Power spectrum

1

1

11

1

1

1

2

2

2

2

3

3

3

3

3

2

4

4

4

4

4

Eb/Io is the Bit Energy we obtain after despreading in the presence of the Noise generated by all other users and the Noise from NodeB equipment.

Eb/No -> Eb = Energy per bit, No = Noise Spectral Density

[ Sensitivity of Base Station]

Uplink Eb/No = Minimum Signal/Noise to achieve any Service

BER (Bit Error Rate) = Function of Eb/No

SNR = C/I = Eb/No - Processing Gain

CS 12.2 CS 64 PS 64 PS 128 PS 384

Bit rate (kbps) 12.2 64 64 128 384

UL Eb/No (dB) 4.9 3 3.2 2.6 2.1

Spreading Factor 256

Processing gain (dB) 25 18 18 15 10

UL C/I (dB) -20 -15 -15 -12 -8

Basic W-CDMA Terminologies

Interference level

Example: 2 UEs at the same distance from the BTS using 2 data rates

Eb/No

requiredS

F =

12

8

Service provided: Speech

Interference level

Eb/No

required

Service provided: Data 144

User 2 needs more power for the UL & DL for the same quality as

user 1

UE2UE1

Speech 8 kbps Data 144 kbpsThe higher the SF, the less power required

Node B

Received powerReceived power

Coverage Limits

SF = 128

Speech 8 kbps Data 64 kbps Data 384 kbps

Node B

SF = 32

SF = 4

The coverage limits are determined by

the Uplink link Budget

Coverage Limits

Channelisation code Scrambling code

Usage Uplink: Separation of physical data (DPDCH) and control channels (DPCCH) from same terminal

Downlink: Separation of downlink connections to different users within one cell

Uplink: Separation of mobile

Downlink: Separation of sectors (cells)

Length 4–256 chips (1.0–66.7 ms)

Downlink also 512 chips

Different bit rates by changing the length of the code

Uplink: (1) 10 ms = 38400 chips or (2) 66.7 ms = 256 chips

Option (2) can be used with advanced base station receivers

Downlink: 10 ms = 38400 chips

Number of codes

Number of codes under one scrambling code = spreading factor

Uplink: 16.8 million

Downlink: 512

Code family Orthogonal Variable Spreading Factor

Long 10 ms code: Gold code

Short code: Extended S(2) code family

Spreading Yes, increases transmission bandwidth

No, does not affect transmission bandwidth

Channelisation and Scrambling Codes

Scrambling code

Channelization code 1



User 1 signal

User 2 signal

User 3 signal

Node B

Codes Multiplexing

1 - Downlink Transmission on a Cell Level

NodeB

Channelization code

2 - Uplink Transmission on a Cell Level

Scrambling code 2

User 2 signal

Scrambling code 3

User 3 signal

Channelization code

Channelization code

Scrambling code 1

User 1 signal

Codes Multiplexing

Channelization and Scrambling Codes

2 data channels(voice, control)

SC3 + CC1 + CC2

2 data channels(14 kbps data, control)

SC4 + CC1 + CC2

3 data channels(voice, video, control)

SC2 + CC1 + CC2 + CC3

3 data channels(voice, video, control)

SC5 + CC1 + CC2 + CC34 data channels

(384 kbps data, voice, video, control)SC6 + CC1 + CC2 + CC3 + CC4

4 data channels(384 kbps data, voice, video, control)

SC2 + CC4 + CC5 + CC6 + CC7

2 data channels(voice, control)

SC1 + CC1 + CC2

1 data channels(control)

SC1 + CC3

VoiceConversation Uplink

Packet Data

Videoconference

Videoconference with Data

Pilot, BroadcastSC1 + CCP + CCB

Pilot, BroadcastSC2 + CCP + CCB

DL Spreading and Multiplexing in WCDMA

User 3

User 2

User 1

BCCH

Pilot X

CODE 1

X

CODE 2

X

CODE 3

X

CODE 4

X

CODE 5

+

X

SCRAMBLINGCODE

RF

SUM

User 2

User 1

BCCH

Pilot

Radio frame = 15 time slots

Time

User 3

3.84 MHzRF carrier

3.84 MHz bandwidth

CHANNELISATION codes:

P-CPICH

P-CCPCH

DPCH1

DPCH2

DPCH3

Physical Layer Structure

Frame #0 Frame #1 Frame #i Frame #4095

System frame = 4096 frames = 40.96 seconds

Slot #0 Slot #1 Slot #j Slot #14

Frame = 15 slots = 10 ms = 38400 chips

Slot = 0.667 ms = 2560 chips

UMTS Frame Format

(38400*1000/10 = 3.84 Mcps)

Parameters WCDMAChip rate 3.84 Mcps

Frame length 10 or 2 ms

Modulation

Downlink: QPSK; 16QAM

Uplink: BPSK

Bandwidth 5 MHz

Vocoder

Algebraic Code Excited

Linear Prediction Coder(ACELP)

Base synchronization Asynchronization

Power control rate 1500 Hz

Cell identification

Unique scrambling code (Gold code)

Channelization code

OVSF code

WCDMA Parameters

Agenda




•Load control


•Packet Scheduler

•Resource Manager

•Power Control

•Handover Control


•Rake receiver

Radio Resource Management

– RRM is responsible for optimal utilisation of the radio resources:

• Transmission power and interference

• Logical codes

– The trade-off between capacity, coverage and quality is done all the time

• Minimum required quality for each user (nothing less and nothing more)Maximum number of users

– The radio resources are continuously monitored and optimised by several RRM functionalities

service quality

cell coverage cell capacity

Optimizationand Tailoring

Handover

Control

Power Control

Resource

Manager

Admission

control

Load control

Packet data

scheduling

Congestion Control

Radio Resource Management

RADIO RESOURCE UTILIZATION

To adjust the transmit powers in upilnk and downlink to the minimum level required to enshure the demanded QoS

Takes care that a connected user is handed over from one cell to another as he moves through the coverage area of a mobile network.

To ensure that the network stays within the planned condition

Let users set up or reconfigure a radio access bearer(RAB) only if these would not overload the system and if the necessary resources are available.

Takes care that a system temporarily going into overload is returned to a non-overloaded situation.

To handle all non-realtime traffic,allocate optimum bit rates and schedule transmission of the packet data, keeping the required QoS in terms of throughput and delays.

To control the physical and logical radio resources under one RNC;to coordinate the usage of the available hardware resouces and to manage the code tree.

Basic RRM functions

* Power Control

* Handover Control

* Congestion Control

* Resource Management

RRM Functionalities

LC Load Control

AC Admission Control

PS Packet Scheduler

RM Resource Manager

PC Power Control

HC HO Control

PC

HCFor each connection/user

LC

AC

For each cell

PS

RM

– LC performs the function of load control in association with AC & PS

– LC updates load status using measurements & estimations provided by AC and PS

– Continuously feeds cell load information to PS and AC;

• Interference levels (UL)

• BTS power level (DL)

LC

AC

PSNRT load

Load change info

Load status

Load Control (LC)

Load Control – Load Status

– Load thresholds set by radio network planning parameters

Overloadthreshold x

Load Targetthreshold y

Po

wer

Time

Load Margin

Overload

Normal load

Measured loadFree capacity

– Checks that admitting a new user will not sacrifice planned coverage or quality of existing connections

– Admission control handles three main tasks

• Admission decision of new connections

– Take into account current load conditions (from LC) and load increase by the new connection

– Real-time higher priority than non-real time

– In overload conditions new connections may be rejected

• Connection QoS definition

– Bit rate, BER target etc.

• Connection specific power allocation (Initial, maximum and minimum power)

Admission Control (AC)

Packet Scheduler (PS)

– PS allocates available capacity after real-time (RT) connections to non-real time (NRT) connections

• Each cell separately

• Based on QoS priority level of the connection

• In overload conditions bit rates of NRT connections decreased

– PS selects allocated channel type (common, dedicated or HSPA)

– PS relies on up-to-date information from AC and LC

– Capacity allocated on a needs basis using ‘best effort’ approach

• RT higher priority

Resource Manager (RM)

– Responsible for managing the logical radio resources of the RNC in co-operation with AC and PS

– On request for resources, from either AC(RT) or PS(NRT), RM allocates:

• DL spreading code

• UL scrambling code

Code Type Uplink Downlink

Scrambling codes

Spreading codes

User separation Cell separation

Data & control channels from same UE Users within one cell

Agenda




•Load control


•Packet Scheduler

•Resource Manager

•Power Control

•Handover Control


•Rake receiver

Power Control

• Concept : Power is a common resource in WCDMA

• Goal : Ensure sufficient received energy per information bit for all communication links

• Strategy : Power control on COMMON CHANNELS ensures there is sufficient coverage to establish connections and transfer date on common transport channels

Power control on DEDICATED CHANNELS (DCH) ensures sufficient connection quality while minimizing impact on other connections.

• Power Control or Rate Control

– Power control strategy (R99): adjust transmitted power while keeping the data rate constant

– Rate control strategy (HSDPA): adjust the data rate while keeping the transmitted power constant

UE 1

UE 2

Before despreading After despreading

Near-Far-Problem

– Up to around 80 dB attenuation between UE1 and UE2

– If UE1 and UE2 transmitted with the same power, UE1 would jam UE2 :

so-called “near-far” effect

– Solution : power control

– Need for an efficient power control able to fight against slow AND fast fading!

Power Control Types

• Open loop power Control

– Initial power setting

• Outer Loop (RNC)

– Adjust quality target dependent on performance

• Inner Loop (fast power control-NodeB)

– compensates for fading channels

– needs dedicated control channel for power control commands

Without power control

PTX

tfading

channel

t

PRX

fading

channel

t

PTX

t

PRX

With power control

UL Outer LoopPower Control

Open Loop Power Control (Initial Access)

Closed Loop Power Control

RNCNode B

UE

DL Outer LoopPower Control

Power Control types

BLER target

Open Loop Power Control

• Controlled by UE.

• Determine UE initial transmission power for random access procedure.

• Not in use when inner loop power control running.

• UE obtain information from network on:

• CPICH power

• Uplink interference level

• Constant value (Default = 2dB)

UE Initial Power = CPICH power – CPICH_RSCP + UL interference + Constant

System information :

CPICH power, UL interference & constant

PRACH Tx power

Power Ramping on PRACH

PRACH

AICH

Preamble Sequence

1st transmitted

preamble

Increase power

until heard

Once preamble is heard,

increase power for

message Message

(Control Part)

Preamble heard

and Acquisition

Indicator sent

UL

DL

powerOffsetP0

powerOffsetP0

powerOffsetPpm

Open Loop Power Control

Inner Closed Loop Power Control

Power Control Bit• Located in UE & NodeB

• Controls power of dedicated physical channels

• Power controls occurs at 1500Hz, thus known as

fast power control

• NodeB and UE continuously measure and compare

SIRmeasured with SIRthreshold value, and inform each

other to increase /reduce its power accordingly.

UE1 UE2 UE3 UE4

With Optimum Power Control

UE1

UE2

UE3

UE4

Without Power Control

Receiv

ed

po

wer

at

No

deB

Receiv

ed

po

wer

at

No

deB

(SIR)measured

NodeB

UE2

UE3

UE1

UE4

SIR threshold

Outer Closed Loop Power Control

• Adjust SIR for every user

• Needed to keep track of changes in radio environment

• Aims to provide required quality

• If SIRthreshold reaches its maximum, system has to perform

- inter-frequency/inter-system handover

- RRC connection release

BER/BLER Value

Change in (SIR)threshold

RNCSIR threshold

Power Control

• TX Power is adjusted regularly so that each connection is received with the required Eb/No of its service– Uplink: Avoid ”Near-Far-Problem“ – Downlink: Power share allocation

• Policy: “No one gets a higher quality (Eb/No) than he needs. Everyone gets exactly the required quality or is not served at all“– no unnecessary increase of interference for other mobiles– no waste of common power resource in the downlink

PC Gain:Lower Eb/No

Importance of Power Control

– Minimizes the Interference and there by enhances capacity and quality.

– It helps allowing as many users as possible while keeping the interference as

minimum as possible

– It maintains the quality of all radio connections by controlling the transmit power in

both the links.

– Power Control aims at using the minimum required SIR for the quality of connection

to remain sufficient. No excessive quality.

– Power Control on common channels ensures that their coverage is sufficient for call

setup

– It provides protection against slow fading and fast fading.

– Efficient power control avoids the near-far problem.

– Power control works efficiently during transmission gap in compressed mode by

bring the SIR back close to the target SIR.

– It helps reducing the battery consumption

Agenda




•Load control


•Packet Scheduler

•Resource Manager

•Power Control

•Handover Control


•Rake receiver

Handover Control (HC)

– HC is responsible for:

• Managing the mobility aspects of an RRC connection as UE moves around the network coverage area

• Maintaining high capacity by ensuring UE is always served by strongest cell

– Soft handover

• MS handover between different base stations

– Softer handover

• MS handover within one base station but between different sectors

– Hard handover

• MS handover between different frequencies or between WCDMA and GSM

Soft/Softer Handover

Soft/softer handover is important for efficient power control. Without soft/softer handover there would be near-far scenarios of a UE penetrating from one cell deeply into an adjacent cell without being power controlled by the latter.

Soft Handover: UE connected to two or more NodeBs at the same time.

Softer Handover: UE connected to two or more sector of the same NodeB.

Macro-Diversity

Softer HandOver

Node B(BTS)

RNC

Data UL

Data UL1Data UL2 Data UL

Data UL

Data DLData DL

Data DL1

Data DL1Data DL2

Data DL

UE

Data DL2

Data UL

CoreNetwork

Macro-Diversity

Soft HandOver Intra RNC

RNC

Data UL1

Data UL1Data UL2

Data UL

Data UL

Data DL

Data DL1

Data DL1

Data DL1Data DL2

Data DL

UE

CoreNetwork

Data DL2

Data UL

Data DL2

Data UL2

Data UL2

Data UL1

Node B(BTS)

Node B(BTS)

• Soft Hand Over Inter RNC: Serving RNC (SRNC) and Drift RNC (DRNC)

Node B(BTS)

SRNC

DRNCNode B(BTS)

Data UL

Data UL

Data ULData UL1

Data UL2

Data UL2

Data UL1Data UL2 Data UL

Data UL

Data DLData DL2

Data DL2

Data DL1

Data DL2

Data DL1

Data DL1Data DL2 Data DL

UE

CoreNetwork

Soft HandOver Inter RNC

Hard Handover

• Hard handovers are typically performed between WCDMA frequencies and between WCDMA and GSM cells

GSM/GPRSGSM/GPRS

f1

f2

f1

f2f2f2

Inter-System Handovers (ISHO)

Inter-Frequency Handovers (IFHO)

In UL selection of the best signal on a frame basis at RNC level -

‘selection diversity’

In DL Maximum Ratio combining due to RAKE receiver at UE

For UL & DL good decorrelation due to different locations of Node Bs

many multipaths

In UL Maximum. Ratio Combining at Node B

In DL Maximum Ratio combining due to RAKE receiver at UE

For UL & DL less decorrelation due to “same” location of sectors less multipaths

Soft HO

Softer HO

Soft/Softer Handover

RNC

RNC

Soft/Softer Handover Power Control

Uplink Power is based on information (TPC bits) from both NodeBs to which the UE is connected. The UE will decrease its output power in all cases except when both NodeBs send increase power commands.

Downlink Power control for both NodeBs is based on one signal (TPC bits) from the UE (it does not distinguish between NodeBs and the decision is base on the combined output from the RAKE receiver

UL Power control DL Power control

Agenda





•Rake receiver

Few Basics….

COVERAGE

CAPACITY QUALITY

POWER

Understanding Power Control…

LOWER Power Per User – HIGHER Number of Users

HIGHER Power Per User – LOWER

Number of Users

Interference…

No or Improper Power Control leads to High interference that impacts Coverage, Capacity and Quality

Power Ctrl

ON

OFF

UL/DL Capacity Limitation

• Scenario 1: Capacity limitation due to UL interference

– The cell can’t serve UE1 because the increase in UL interference by adding the new user would be too high, resulting in a high risk of drops

• Scenario 2: Capacity limitation due to DL power

– The cell can’t serve UE2 because it’s using all its available power to maintain the connections to the other UEs

UE1

UE2

Scenario 1 Scenario 2

Node B Node B

Fully loaded system

Unloaded system

Cell Breathing

The more traffic, the more interference and the shorter the distance must be between the Node B and the UE.

The traffic load changes in the system causes the cells to grow and shrink with time

Agenda





•Rake receiver

Multipath Propagation

2t

Time Dispersion

t1t

0t

2t

3t

Maximum ratio combining

1t

0t

3t

Multiple paths possibly cause destructive interference between different replica of the desired signal

The Rake Receiver

• Each multi-path component is called a “finger”

• Estimation of radio channel properties for each finger:

– delay

– amplitude and

– Phase

• The Rake receiver combines multi-path components by coherent combining of multi-path components belonging to the respective user.

Maximum ratio combining – RAKE

Each finger tracks a different multipath component and other cells during Soft Handover

A maximum ratio combining produces the output

Search Finger is used to determine when to perform handovers

C

O

M

B

I

N

E

R

Power measurements of neighbouring NodeBs

Sum of individual multipath components

Finger #1

Finger #2

Finger #3

Finger #N

Buffer/delay

CorrelatorsChannel

Searcher Finger

TX

D(t)

Delay t0

Delay t1

C(t-t0)

+C(t-t1)

Delay (t1)

RX

C(t-tn)

Delay (t0)

Delay (tn)RX

RX

C(t)

t0

t1

tn

Take advantage of multipath diversity

BTS

Taking advantage of Multipath: Rake Receiver

UE

Spreading &

Scrambling

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42164892 Intoduction WCDMA Fundamantels[1]

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