Examining how to Minimize the Impact of Cell Breathing on UMTS ...

How to Minimize the Impact of Cell Breathingon UMTS Networks

How to Minimize the Impact of Cell Breathingon UMTS Networks

Yannick DUPUCHAlcatel - Mobile Networks Division

GSM/UMTS Project Manager

Yannick DUPUCHAlcatel - Mobile Networks Division

GSM/UMTS Project Manager

IEEE Workshop on Applications and Services inWireless Networks 2002

July 3rd - 5th, 2002

IEEE Workshop on Applications and Services inWireless Networks 2002

July 3rd - 5th, 2002

How to minimize the impact of cell breathing effect on UMTS network / July 4th / 2 All rights reserved © 2002, Alcatel

Agenda Agenda

�Facing the Multimedia traffic increase

� Cell breathing and cell range evolution

� Strategic Cell Radius

�Upgrade your Network

� Advanced Radio Features

� Elaborating the deployment strategy


� Various data rates (from Voice 12.2kbps up to 384Kbps)

� Various QoS and GoS (blocking, delay, throughput, BLER)

� Various connection types (Real Time and Non Real Time)

� Various traffic asymmetry and activity behaviour.

Node BAir interface

Voice (CS/2%) File transfer (PS/5s)Web browsing (PS/3s)Video conference (CS/2%)Shopping on line (PS/1s)Interactive games (CS/1%)

3G UE

Cell BreathingMultiservice Traffic characteristicCell BreathingMultiservice Traffic characteristic

MultiserviceMultiserviceMultiservice

Different Data ratesDifferent Data ratesDifferent Data rates

Different SensitivitiesDifferent SensitivitiesDifferent Sensitivities

Different FootprintsDifferent FootprintsDifferent Footprints

Voice and Low Data Rate (eg up to 64kb/s)

Medium Data Rate(eg 144kb/s)

High Data Rate (eg 384kb/s)

� Different footprints for different services� Different footprints for different services


Service Coverage:� Blue: Voice Only� Green: Voice and CS64� Red: Voice, CS 64 and PS384

Cell BreathingMultiservice EnvironmentCell BreathingMultiservice Environment

1000 subs/km2 - Year 5

300 subs/km2 - Year 3

100 subs/km2 - Year 1Seamless Coverage

Coverage for each service is traffic

dependent� Cell shrinkage


From traffic forecast to coverage predictionIterative Link Budget DimensioningFrom traffic forecast to coverage predictionIterative Link Budget Dimensioning

W-CDMARadio Parameters

UL & DL Cell rangeUL & DL Cell range

InterferenceInterference

TRAFFIC ANALYSISTRAFFIC ANALYSIS LINK BUDGET ANALYSISLINK BUDGET ANALYSISFinal

UL & DLCell

Range

FinalFinalUL & DLUL & DL

CellCellRangeRangeC

ell R

an

ge

ass

um

pti

on

Cell R

an

ge

Cell R

an

ge

ass

um

pti

on

ass

um

pti

on

Multiservice Trafficinputs

UL analysis

DL analysis

UL traffic

DL traffic

Iterative processuntil convergence

> Use of Multiservice traffic modelling and iterative interference calculation

in both uplink and downlink to get the evolution of the cell range


Strategic cell radiusFixing a time variant parameterStrategic cell radiusFixing a time variant parameter

> Strategic cell

range will define

the deployedinter-sitedistance per

environment

Dense Urban / Cell range = f(Phases)

0.55

0.6

0.65

PHO PH1 PH2 PH3Phases

Cel

l ran

ge (k

m)

Voice with 1 carrier

Traffic increases

Example ofstrategic cell radius

�

�

�

�

�

�

�

Site

Site

Site

Site

Site

Site

Site

Seamless coverage

Holes in coverage

1.5xR


Advanced FeaturesAvoiding Cell Breathing problems by timely upgradeAdvanced FeaturesAvoiding Cell Breathing problems by timely upgrade

> Anticipate holes through coverage prediction

> Avoid holes by timely upgrade

� In case of Downlink limitation

� TX Diversity

� High power amplifier

� In case of Downlink limitation

� TX Diversity

� High power amplifier

� In case of Uplink limitation

� Tower Mounted Amplifier (TMA)

� 4 Way RX Diversity

� Multi User Detection, MUD

� In case of Uplink limitation

� Tower Mounted Amplifier (TMA)

� 4 Way RX Diversity

� Multi User Detection, MUD

�For either Uplink or Downlink

limitation:

� Adding carriers

� Sectorisation

� Adding sites (densification)

� Smart antennas

�For either Uplink or Downlink

limitation:

� Adding carriers

� Sectorisation

� Adding sites (densification)

� Smart antennas


Tower Mounted AmplifierUplink Coverage GainTower Mounted AmplifierUplink Coverage Gain

0

2

4

6

8

10

12

14

16

18

0 0.2 0.4 0.6 0.8 1

Cell Range R (km)

Tota

l In

terf

ere

nce

I (

dB

) Link Budget Curve with TMALink Budget Curve w/o TMAI(R) for High_TrafficI(R) for Low_Traffic

Node B

Feeder

Antenna

Tx / Rx

Duplexer

Duplexer

Tx Rx

TMA

Typical reduction of the required numberof sites:

– ~40% for low traffic scenario– ~30% for high traffic scenario


4-RX diversity on UplinkUplink Coverage Gain4-RX diversity on UplinkUplink Coverage Gain

Link Budget Curve with 4RxDiv

I(R) for High_Traffic w/o 4RxDiv

I(R) for High_Traffic with 4RxDivI(R) for Low_Traffic w/o 4RxDiv

I(R) for Low_Traffic with 4RxDiv

0

1

2

3

4

5

6

7

8

9

10

0 0,2 0,4 0,6Cell Range R (km)

Tot

al In

terf

eren

ce I

(dB

)

Link Budget Curve w/o 4RxDiv

Typical reduction of the required number

of sites:– ~30% for low traffic scenario– ~40% for high traffic scenario

Distance d

Rxdiv1 Rxdiv2 Rxdiv3 Rxdiv4

SpaceDiversity

PolarisationDiversity

PolarisationDiversity

Xpolantenna 2

Xpolantenna 1


0

5

10

15

20

25

30

35

40

45

100 200 300 400 500 600 700 800 900

Throughput NRT 128 (kbps)

Tran

smit

pow

er (W

att)

RURAL 7 km

RURAL 5 km

SUBURBAN 1,3 km

URBAN 0,5 km

URBAN DENSE 0,35 km

Capacity gain

High Power AmplifierImpact of Node B power on DL capacityHigh Power AmplifierImpact of Node B power on DL capacity

> Negligibleimpact in urbanareas

> Visible gain onlyin low densityrural areas

Tran

smit

pow

er (W

att)

per c

arrie

r

Sector Capacity

RuralRural

UrbanUrban


0%

10%

20%

30%

40%

50%

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Cell range (km)

Cap

acity

gai

n (%

)

From 6.7W per carrier to11.7W per carrier (3 carriers)

From 10W per carrier to 17.5Wper carrier (2 carriers)

From 20W per carrier to 35Wper carrier (1 carrier)

High Power AmplifierDL Gain in multicarrier configurations - UrbanHigh Power AmplifierDL Gain in multicarrier configurations - Urban

20W vs. 35W at antenna connector: NRT 128 in Urban

negligible gain for 1 carrier

small gain for 3 carriers

UplinkCoverage

limited cellranges


> Performance gain of TX diversityfeature consists of three aspects:

� Doubling the TX power by adding apower amplifier

� Reducing the required transmit powerfor each downlink channel (transmitpower raise due to fast fading isreduced)

TX Diversity on DownlinkPerformance GainTX Diversity on DownlinkPerformance Gain

� Improving the required received Eb/N0

(slight reduction for open loop

TxDiv, higher for closed loop TxDiv)6

7

8

9

3 6 10 25 50 120

Targ

et R

x Eb

/N0

(dB)

Speed (km/h)

Speech 8 kbps, 1 rx antenna, downlink, pedestrian A

Without Tx diversitySTTD

0.8 dB

TEU

PA

TEU

PA

Power Amplifier Antenna

Antenna 1

Antenna 2

20 W

20 W

TX Bus

TX1

TX1div


0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Cell range (km)

Cap

acity

gai

n by

dou

blin

g th

e m

ax. d

ownl

ink

tran

smit

pow

er (

%)

From(20W,1Carrier)To (40W,1Carrier)

TX Diversity on DownlinkGain on Downlink Capacity - ExampleTX Diversity on DownlinkGain on Downlink Capacity - Example

> Gain highly dependent on diversity technique (open or closed loop)and multipath profile (Pedestrian>>Vehicular)

• Pure Diversity gain in capacity: ~8%

• Gain through 2nd PA:

dependent on cell range (curve)

Example for typical cell range(0.55km):

8%+3%=11% total gain

UplinkCoverage limited

cell ranges

Example:STTD - Space-Time transmit diversity (open loop)Vehicular A, NRT 128, Urban,


Adding a carrierUplink coverageAdding a carrierUplink coverage

> Uplink Coverage:

• Link Budget curvestays the same, trafficcurve depends on #of carriers

0

2

4

6

8

10

12

14

16

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Cell Range R (km)

Tot

al In

terf

eren

ce I

(dB

)

link budget curveI(Traffic),1 carrierI(Traffic), 2 Carriers

Carrier config Dense Urban Rural Dense Urban Rural1C -> 2C 5% 10% 20% 20%2C -> 3C 3% 5% 15% 15%

Low traffic High trafficUL Coverage gain


Adding a carrierDownlink capacityAdding a carrierDownlink capacity

� Significant increase of downlink capacity

� Exact gain depends on the hardware configuration (Nb of PA persector, # of carriers, etc…) and cell range

� Adding a carrier implies:reducing power per carrier(20W � 2x10W) PA

Carrier

Power Amplifier

Antenna

Antenna 1

10 W per carrier

TXC1

C2

0%

25%

50%

75%

100%

0 0.2 0.4 0.6 0.8Cell range (km)

Cap

acity

gai

n (%

)

From 1 carrier (20W p.c.)to 2 carriers (10W p.c.)

From 2 carriers (10W p.c.)to 3 carriers (6W p.c.)

UplinkCoverage

limited cellranges

UplinkCoverage

limited cell ranges

� Adding a carrier is not only adownlink feature, but will bringfor fixed intersite distanceuplink capacity gain as wellMost powerful enhancementfeature


Deployment strategyIncumbent OperatorDeployment strategyIncumbent Operator

Traffic forecast

GSM Cell range=strategic cell radiusGSM Cell range=strategic cell radius

Holes or capacity problems?

Coverage and Capacity analysis

Which limitation?

Apply UL feature(TMA, 4RXDiv, MUD)(if not yet used)

Apply DL feature(TxDiv, HPA)(if not yet used)

Add a carrier(if still available)

Look at next phase

Start: Phase 0

UL DL both UL&DL

YES

NO

Maximize the re-use of existing GSM sites


Deployment strategyGreenfield OperatorDeployment strategyGreenfield Operator

Evaluate Cell Ranges(for all traffic phases and scenarios)

Identify suitable strategicranges

Apply possible deploymentscenarios

(service deployment,advanced features upgrade)

Build business cases

Select the solution that best fitsyour business requirements

There is no unique solutionfor strategic cell range and

deployment strategy, the finalchoice is an (individual)

strategic decision!


ConclusionConclusion

> The upgrade plan is not finished at dimensioning stage:

continuous adaptation is required through• Monitoring traffic• Regularly updating the traffic forecast• Adjusting the upgrade strategy

> Analytical dimensioning techniques can be used forpredicting and avoiding potential problems due to cellbreathing (� upgrade strategy)

> The network evolution can be considered already atdimensioning stage

Yannick DUPUCH

UMTS Project ManagerMobile Networks [email protected]

Thank you for your attentionThank you for your attention

Examining how to Minimize the Impact of Cell Breathing on UMTS ...

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