02 RN31542EN10GLA0 WCDMA Fundamentals

1 © NSN Siemens Networks RN31542EN10GLA0

WCDMA Fundamentals3GRPESS – MODULE 1


Module 1 – WCDMA Fundamentals

Objectives

• After this module the participant shall be able to:-

• Understand the main cellular standards and allocated frequency bands

• Understand the main properties of WCDMA air interface including HSPA technology

• Recognize the main NSN RRM functions and their main tasks


Module Contents

• Standardisation and frequency bands

• Main properties of UMTS Air Interface

• Overview of NSN Radio Resource Management (RRM)

• HSPA technology


Module Contents

• Standardisation and frequency bands– Standardisation of 3G cellular networks

– IMT-2000 frequency allocations

– UMTS – FDD Frequency band evolution



• HSPA technology


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


IMT-2000 frequency allocations

2200 MHz20001900 1950 2050 2100 21501850

JapanIMT-2000

PH

S

IMT-2000

ITU

Mob

ile

Sate

llit

eIMT-2000 IMT-2000

EuropeUMTS(FDD)D

EC

T

UM

TS

(T

DD

)

GSM1800 U

MTS

(T

DD

)UMTS(FDD)

USA

PC

S

un

licen

sed

PCSPCS

UM

TS

(T

DD

)IM

T-2

00

0

(TD

D)

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e

Mob

ile

Sate

llit

e


UMTS – FDD Frequency band evolution

• Release 99– I 1920 – 1980 MHz 2110 –2170 MHz UMTS only in Europe,

Japan– 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

Not supported by RU10 RAN


Module Contents


• Main properties of UMTS Air Interface– UMTS Air interface technologies

– WCDMA – FDD

– WCDMA vs. GSM

– CDMA principle

– Processing gain

– WCDMA codes and bit rates


• HSPA technology


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


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


WCDMA Technology

5 M Hz

3.84 M Hz

f

5+5 MHz in FDD mode5 MHz in TDD mode

Freq

uenc

y

TimeDirect Sequence (DS) CDMA

WCDMA Carrier

WCDMAWCDMA5 MHz, 1 carrier5 MHz, 1 carrier

TDMA (GSM)TDMA (GSM)5 MHz, 25 carriers5 MHz, 25 carriers

Users share same time and frequency


UMTS & GSM Network Planning

GSM900/1800: 3G (W CDM A):


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


Multiple WCDMA carriers – Layered network

F1

F2

F2

F3

F3

F3

Micro BTSMacro BTS

Pico BTSs

1 - 10 km

50 - 100 m200 - 500 m


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

Despreading

Despreading

CDMA principle - Chips & Bits & Symbols


Energy Box

Frequ

ency

Ban

d

Duration (t = 1/Rb)

Po

wer

/Hz

Originating Bit Received BitEnergy per bit = Eb = const

Higher spreading factor Wider frequency band Lower power spectral density

BUT

Same Energy per Bit


FrequencyPow

er d

ensi

ty (

Wat

ts/H

z)

Unspread narrowband signal Spread wideband signal

Bandwidth W (3.84 Mchip/sec)

User bit rate R

sec84.3 MchipconstW

R

WdBGp Processing gain:

Spreading & Processing Gain


Frequency (Hz)

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

Packet data user (R=384 kbit/s)

Pow

er

den

sity

(W

/Hz)

R

Frequency (Hz)

Gp=W/R=24.98 dB

Pow

er

den

sity

(W

/Hz)

R

Gp=W/R=10 dB

• Spreading sequences have a different length• Processing gain depends on the user data rate

Processing Gain Examples


Transmission Power

Frequency

5MHz

Power density

Time

High bit rate user

Low bit rate user


WCDMA Codes

• In WCDMA two separate codes are used in the spreading operation

– Channelisation code

– Scrambling code

• Channelisation code– DL: separates physical channels of different users and common channels,

defines physical channel bit rate

– UL: separates physical channels of one user, defines physical channel bit rate

• Scrambling code– DL: separates cells in same carrier frequency

– UL: separates users


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


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

...


Half rate speechFull rate speech

128 kbps384 kbps

2 Mbps

Symbolphyb RR 2_SF

WRSymbol

(QPSK modulation)

Physical Layer Bit Rates (DL)


Physical Layer Bit Rates (DL) - HSDPA

• 3GPP Release 5 standards introduced enhanced DL bit rates with High Speed Downlink Packet Access (HSDPA) technology

– Shared high bit rate channel between users – High peak bit rates

– Simultaneous usage of up to 15 DL channelisation codes (In HSDPA SF=16)

– Higher order modulation scheme (16-QAM) Higher bit rate in same band▪ 16-QAM provides 4 bits per symbol 960 kbit/s / code physical channel peak

rate

Coding rateCoding rate

QPSKQPSK


1/41/4

2/42/4

3/43/4

5 codes5 codes 10 codes10 codes 15 codes15 codes

600 kbps600 kbps 1.2 Mbps1.2 Mbps 1.8 Mbps1.8 Mbps

1.2 Mbps1.2 Mbps 2.4 Mbps2.4 Mbps 3.6 Mbps3.6 Mbps


16QAM16QAM

2/42/4

3/43/4

4/44/4




HSDPA


Physical Layer Bit Rates (UL) - HSUPA

• 3GPP Release 6 standards introduced enhanced UL bit rates with High Speed Downlink Packet Access (HSUPA) technology

– Fast allocation of available UL capacity for users – High peak bit rates

– Simultaneous usage of up to 2+2 UL channelisation codes (In HSUPA SF=2 – 4)


1/21/2

3/43/4

4/44/4

1 x SF41 x SF4 2 x SF42 x SF4 2 x SF22 x SF2 2 x SF2 + 2 x SF4

2 x SF2 + 2 x SF4

480 kbps480 kbps 960 kbps960 kbps 1.92 Mbps1.92 Mbps 2.88 Mbps2.88 Mbps

720 kbps720 kbps 1.46 Mbps1.46 Mbps 2.88 Mbps2.88 Mbps 4.32 Mbps4.32 Mbps

960 kbps960 kbps 1.92 Mbps1.92 Mbps 3.84 Mbps3.84 Mbps 5.76 Mbps5.76 Mbps


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


Scrambling Codes & Multipath Propagation

Scrambling code C1

Scrambling code C2

C 1+ 3

C1+2C1+

1

C2

UE has simultaneous connection to two cells (soft handover)


RAKE Receiver

• Combination or multipath components and in DL also signals from different cells

Del

ay

1Code used

for theconnection

Rx

Output

Finger

t

Cell-1

Cell-1

Cell-1

Cell-2

Rx

Rx

Rx

Finger

Finger

Finger

Del

ay

2

Del

ay

3


Channelisation and Scrambling Codes


Module Contents



• Overview of NSN Radio Resource Management (RRM)– Load control

– Admission Control

– Packet Scheduler

– Resource Manager

– Power Control

– Handover Control

• HSPA technology


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


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

Pow

er

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 UEUsers within one cell


Power control (PC) in WCDMA

• Fast, accurate power control is of utmost importance – particularly in UL;

– UEs transmit continuously on same frequency Always interference between users

– Poor PC leads to increased interference reduced capacity

• Every UE accessing network increases interference– PC target to minimise the interference Minimize transmit power of each

link while still maintaining the link quality (BER)

• Mitigates 'near far effect‘ in UL by providing minimum required power for each connection

• Power control has to be fast enough to follow changes in propagation conditions (fading)

– Step up/down 1500 times/second


Uplink power control target

Minimise required UL received power minimised UL transmit power and interference

UE1 UE2

min(Prx1)

min(Prx2)

&

About equal when

Rb1 = Rb2

Target:

Ptx1

Ptx1


Power Control types

• Power control functionality can be divided to three main types

• Open loop power control– Initial power calculation based on DL pilot level/pathloss measurement by UE

• Outer (closed) loop power control– Connection quality measurement (BER, BLER) and comparison to QoS target

– RF quality target (SIR target) setting for fast closed loop PC based on connection quality

• Fast closed loop power control– Radio link RF quality (SIR) measurement and comparison to RF quality target

(SIR target)

– Power control command transmission based on RF quality evaluation

– Change of transmit power according to received power control command


UL Outer LoopPower Control

Open Loop Power Control (Initial Access)

Closed Loop Power Control

RNC

BS

MS

DL Outer LoopPower Control

Power Control types

BLER target


Power control in HSPA

• In HSDPA (DL) the transmit power from base station is kept constant and the signal modulation and coding is adapted according to the channel conditions

– 2 ms interval 500 Hz

• In HSUPA (UL)– The power control of HSUPA channels in UL utilises both

▪ Fast closed loop power control

▪ Outer loop power control

– Both work according to similar principles as the R99 power control


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

• UE is simultaneously connected to 2 to 3 cells during soft handover

• Soft handover is performed based on UE cell pilot power measurements and handover thresholds set by radio network planning parameters

• Radio link performance is improved during soft handover

• Soft handover consumes base station and transmission resources

BS1

BS2

BS3

Rec

eive

d s

ign

al s

tren

gth

BS3

Distance from BS1

Threshold

Soft handover

BS2

BS1


Hard handover

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

GSM/GPRSGSM/GPRSGSM/GPRSGSM/GPRS

f1f1

f2f2

f1f1

f2f2f2

f2f2f2

Inter-System handovers (ISHO)

Inter-Frequency handovers (IFHO)


Module Contents




• HSPA technology


Module Contents

HSPA technology

• Channel types• Physical Channels

• Principle of HSPA


Node BU

plin

k an

d D

ownl

ink

Ded

icat

ed C

hann

els

The introduction of 3G made use of uplink and downlink dedicated channels to transfer user plane and control plane data in CELL_DCH

Applicable to

• All 3GPP Releases

Uplink air-interface capacity defined by maximum planned increase in uplink interference

Downlink air-interface capacity defined by downlink transmit power capability

Cell_DCH

CS and PS services

Channel Types for User Plane Data (R99)


Node B

In R5 3G evolved to include HSDPA for transferring packet switched user plane data in the downlink direction

Applicable to

• 3GPP Release 05

• NSN RAS05, RAS05.1

HSDPA makes use of a downlink transmit power allocation and so has a direct impact upon downlink capacity

The resource shared between multiple HSDPA users is the HSDPA downlink transmit power

The Node B scheduler assigns timeslots & codes to specific UE to allow access to the HSDPA downlink transmit power

Upl

ink

Ded

icat

ed

Cha

nnel

s

Cell_DCH

HS

DP

A

PS services CS services continue to use R99 dedicated channels



Node B

• 3G has further evolved to include HSUPA for transferring packet switched user plane data in the uplink direction

• Applicable to

– 3GPP Release 06

– NSN RAS06, RU10

• HSUPA makes use of a uplink interference allocation and so has a direct impact upon uplink capacity

• The resource shared between multiple HSUPA users is the uplink interference

• The Node B scheduler assigns transmit power ratios to specific UE to allow a contribution towards the total increase in uplink interference

HS

UP

A

Cell_DCH

HS

DP

A

PS services CS services continue to use R99 dedicated channels



Module Contents

HSPA technology

• Channel types

• Physical Channels• Principle of HSPA


Node B

DP

DC

HD

PC

CH

UL CHANNELS

DPCH includes• DPDCH• DPCCH – Pilot, TFCI, FBI, TPC

DPDCH encapsulates• Signalling radio bearers• User plane radio bearers

DL CHANNELS

DPCH includes• DPDCH• DPCCH - Pilot, TFCI, TPC


DP

DC

HD

PC

CH

R99 DPCH

Dedicated

Physical Channels for R99 UE


Node B

UL CHANNELS

DPCH includes• DPDCH• DPCCH – Pilot, TFCI, FBI, TPC• HS-DPCCH – CQI, ACK/NACK


DL CHANNELS

DPCH includes• DPDCH• DPCCH - Pilot, TFCI, TPC

DPDCH encapsulates• Signalling radio bearers

HS-PDSCH encapsulates• User plane radio bearers

HS-SCCH provides• Channelisation code set, modulation scheme,

transport block size, HARQ process, redundancy and constellation version, new data indicator, UE identity

1-15

x H

S-P

DS

CH

1-4

x H

S-S

CC

H

DP

DC

HD

PC

CH

HS

-DP

CC

H

DP

DC

HD

PC

CH

HSDPAAssociated DPCH

Dedicated Common

Physical Channels for Rel5 / Rel6 HSDPA UE


Node B

1-15

x H

S-P

DS

CH

1-4

x H

S-S

CC

H

DP

DC

HD

PC

CH

HS

-DP

CC

H1,

2,4

x E

-DP

DC

HE

-DP

CC

H

F-D

PC

H

Dedicated Common

E-D

CH

RG

CH

E-D

CH

AG

CH

E-D

CH

HIC

H

UL CHANNELS

E-DPCH includes• E-DPDCH• E-DPCCH – E-TFCI, RSN, Happy Bit

DPCH includes• DPDCH• DPCCH – Pilot, TFCI, FBI, TPC• HS-DPCCH – CQI, ACK/NACK

E-DPDCH encapsulates• User plane radio bearers

DPDCH encapsulates• Signalling radio bearers

Physical Channels for Rel6 HSPA UE (UL)


Node B

1-15

x H

S-P

DS

CH

1-3

x H

S-S

CC

H

DP

DC

HD

PC

CH

HS

-DP

CC

H1,

2,4

x E

-DP

DC

HE

-DP

CC

H

F-D

PC

H

Dedicated Common

E-D

CH

RG

CH

E-D

CH

AG

CH

E-D

CH

HIC

H

DL CHANNELS

DPCH includes• F-DPCH – TPC• E-DCH RGCH• E-DCH HICH

E-DCH AGCH encapsulates• Absolute grant value, absolute grant scope

HS-PDSCH encapsulates• User plane radio bearers

HS-SCCH provides• Channelisation code set, modulation

scheme, transport block size, HARQ process, redundancy and constellation version, new data indicator, UE identity

Physical Channels for Rel6 HSPA UE (DL)


Module Contents

HSPA technology

• Channel types

• Physical Channels

• Principle of HSPA


HSxPA Motivation and General Principle Improved performance and spectral efficiency in DL and UL by introducing a shared channel principle:

• Significant enchancement with peak rates up to 14.4 Mbps (28 Mbps in Rel7) in DL, and 2 Mbps (11.5 Mbps with 16QAM) in UL

• Huge capacity increase per site; no site pre-planning necessary

• Improved end user experience: reduced delay/latency, high response time

HSDPA (3GPP Rel5)

Fast pipe is shared among UEs

Scheduling A

,B,C

HSUPA (3GPP Rel6)

Dedicated pipe for every UE in ULPipe (codes and grants) changing with timeE-DCH scheduling

E-DCH -

A

E-DCH -

B

E-DCH -

C

Rel. 99

DCH -A

DCH -B

DCH -C

Dedicated pipe for every UE


HSDPA Overview

15 Code Shared

transmission

16QAMModulation

TTI = 2 ms Hybrid ARQwith incr. redundancy

Fast Link Adaptation

AdvancedScheduling

BenefitHigher Downlink Peak rates: 14 Mbps

Higher Capacity: +100-200%Reduced Latency: ~75 ms


• HSDPA power is limited by the PtxMaxHSDPA parameter

Cell maximum TX power

Common chs

HSDPA

Maximum HSDPA power (PtxMaxHSDPA)

Non-HSDPA power

Ptx

Time

Cell maximum TX power

Common chs

HSDPA

Non-HSDPA power

Ptx

Time

• HSDPA power is not limited, all available power can be allocated to HSDPA

• Still PtxMaxHSDPA can be used to limit

HS-PDSCH Transmit power

The Packet Scheduler is responsible for determining the transmission power on the HS-PDSCH channels• Dynamic HSDPA power allocation is always used in BTS

– HSDPA power can be limited with PtxMaxHSDPA• HSDPA Dynamic Resource Allocation feature is activated with RNC parameter

HSDPADynamicResourceAllocation

– Disabled: PtxMaxHSDPA sent to BTS and used to limit the maximum HSDPA power– Enabled: No power limitation sent to BTS, all available power allocated to HSDPA


Maximum code allocation for HSDPA

SF=1

SF=2

SF=4

SF=8

SF=16

SF=32

SF=64

SF=128

SF=256

15 HS-PDSCH codes15 HS-PDSCH codes

Up to three HS-SCCH codesUp to three HS-SCCH codesCodes for common channels in the cellCodes for common channels in the cell

Codes for associated DCHs and non-HSDPA users

Codes for associated DCHs and non-HSDPA users

Used by 2 HSDPA UEs no SF256 available for the 3rd UE for

associated DCH

Used by AMR user only one SF128 code remains for associated

DCH

Used by HSDPA UE as associated DCH and HS-SCCH

Case1:

Case2:

Case1+2:

• Code tree limitation makes it hard to have 15 codes allocated for HSDPA– Still commonly 14 or 12 or lower amounts are easily available– Note that current terminals support only 10 codes so 15 codes means more than 1 users per TTI

• 15 codes is available but not commonly for cells where has reasonable high traffic (noticing terminal limitation 10 codes, thus fully utilise 15 codes needs minimum 2 HSDPA users)

– Case 1: Allocation of 15 is not possible when more than 2 HSDPA users are active (i.e. 3 HSDPA users)– Case 2: Allocation of 15 is not possible (with two HSDPA users) when 1 AMR12.2 user exists in the cell


HSDPA - UE Categories

• QPSK and 16QAM modulation with multicode transmission used to achieve high data rates

• 12 different UE categories defined, categories are characterised by– Number of parallel codes supported

– Minimum inter-TTI interval

• Theoretical peak bit rate up to 14.4 Mbps for category 10 UE using 15 codes and 16QAM


HS-PDSCHHS-PDSCHHS-PDSCH

HS-PDSCH

HSDPA Code Multiplexing

• With Code Multiplexing, maximum of three UEs can be scheduled during one TTI from single cell

• Multiple HS-SCCH channels (max 3 in RAS06)– One for each simultaneously receiving UE

• Available HS-PDSCH codes and HS-PDSCH power of cell are divided between UEs

• HS-PDSCH codes actually used depends on the channel conditions of a UE

• Important when cell supports more codes than UEs do

– Cell supports 15 HS-PDSCH codes, Cat6 and Cat8 UEs => 3 users can be scheduled on TTI

• BTS must also be capable of 10/15 codes in order to dynamically adjust HS-PDSCH codes

HS-PDSCH

cat 6

HS-PDSCH

HS-PDSCH

HS-PDSCH

HS-PDSCH

HS-PDSCH

HS-SCCH

HS-SCCH

cat 6 cat 6 cat 6cat 8

HS-SCCH

HS-PDSCH

HS-PDSCH

HS-PDSCHHS-PDSCH

HS-PDSCH


HSUPA Overview

TTI = 10 ms1-4 Code Multi-Code

transmission

FastPower Control

Hybrid ARQwith incr. redundancy

NodeB ControlledScheduling

BenefitHigher Uplink Peak rates: 2.0 Mbps

Higher Capacity: +50-100%Reduced Latency: ~50-75 ms


HSUPA - UE Categories

• BPSK modulation with multicode transmission used to achieve high data rates

• 6 different UE categories defined, categories are characterised by– Number of parallel codes supported

– Support of 2ms TTI - 10ms TTI supported by all the HSUPA UEs

• Theoretical peak bit rate up to 5.74 Mbps for category 6 UE using 2 ms TTI– No coding and no retransmissions - all bits must be delivered correctly over the air…

11484

20000

20000

5772

20000

14484

2798

14484

7110

Transport Block size

2 Mbps102 x SF24

2.89 Mbps22 x SF24

1.45 Mbps102 x SF42

1.40 Mbps22 x SF42

2 Mbps102xSF2 + 2xSF46

6

5

3

1

HSUPACategory

2

10

10

10

TTI

2xSF2 + 2xSF4

2 x SF2

2 x SF4

1 x SF4

Codes x Spreading

5.74 Mbps

2 Mbps

1.45 Mbps

0.71 Mbps

Data rate


HSPA mobility

HSDPA

• Soft handover on associated DCH channels (signalling, UL data)

• Serving cell change for HSDPA data channel– Connected only to one cell at a time

HSUPA

• Soft handover utilised for uplink channels as required due to near-far problem

• Only Serving Cell can allocate more UL capacity/power

HS-SCCH

HS-PDSCH

DPCH

DPCHServing HS-DSCH cell

Notice that soft/softer handoveris not supported for HS-SCCH/HS-PDSCH


UL DCH vs HSDPA vs HSUPA Concepts

HSDPAHSDPA HSUPAHSUPA

ModulationModulation QPSK and 16-QAMQPSK and 16-QAM BPSK and Dual-BPSKBPSK and Dual-BPSK

Soft handoverSoft handover NoNo YesYes

HSUPA is like “reversed HSDPA”, except

Fast power control

Fast power control NoNo YesYes

SchedulingScheduling Point tomultipoint

Point tomultipoint

Multipoint to point

Multipoint to point

Non-scheduled transmission

Non-scheduled transmission NoNo Yes, for minimum/

guaranteed bit rate

Yes, for minimum/guaranteed bit rate

Required for near-far avoidance

Efficient UE power amplifier

Scheduling cannot be as fast as in HSDPA

Similar to R99 DCH but with HARQ

HSUPA could be better described as Enhanced DCH in the uplink than “reversed HSDPA”

Feature

Variable spreading factor

Fast power control

Adaptive modulation

BTS based scheduling

DCH

Yes

Yes

No

No

HSUPA

Yes

Yes

No

Yes

Fast L1 HARQ No Yes

HSDPA

No

No

Yes

Yes

Yes

Multicode transmission Yes(No in practice)

Yes Yes

HSUPA (E-DCH) is an uplink DCH with BTS-based HARQ and scheduling and true multicode support

Soft handover Yes Yes No(associated DCH only)


Module 1 – WCDMA Fundamentals

Summary

• Radio interface technology of UMTS is WCDMA with FDD and TDD versions

• WCDMA networks can be built on European, US-based and Asian/Japanese frequency bands

• WCDMA air interface utilises combination of two spreading codes

• Radio Resource Management is responsible of efficient utilisation of radio resources while offering required quality of service to users

• HSPA technology can provide higher air interface efficiency

02 RN31542EN10GLA0 WCDMA Fundamentals

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