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How to Minimize the Impact of Cell Breathing
on UMTS Networks
IEEE Workshop on Applications and Services in
Wireless Networks 2002
July 3rdrd - 5thth, 2002
Yannick
Yannick DUPUCH
DUPUCH
Alcatel
Alcatel -- Mobile
Mobile Networks
Networks Division
Division
GSM/UMTS
GSM/UMTS Project
Project Manager
Manager
Agenda
t Facing
the Multimedia traffic increase
w
Cell breathing and cell range evolution
w
Strategic Cell Radius
t Upgrade
your Network
w
Advanced Radio Features
w
Elaborating the deployment strategy
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 2
All rights reserved © 2002, Alcatel
Cell Breathing
Multiservice Traffic characteristic
t
Various data rates (from Voice 12.2kbps up to 384Kbps)
t
Various QoS and GoS (blocking, delay, throughput, BLER)
t
Various connection types (Real Time and Non Real Time)
t
Various traffic asymmetry and activity behaviour.
3G UE
Voice (CS/2%)
File transfer (PS/5s)
Web browsing (PS/3s)
Video conference (CS/2%)
Shopping on line (PS/1s)
Interactive games (CS/1%)
Multiservice
Multiservice
Different
DifferentData
Datarates
rates
Different Sensitivities
Different Sensitivities
Different
DifferentFootprints
Footprints
Node B
Air interface
t
t Different
Different footprints
footprints for
for different
different services
services
High Data Rate
(eg 384kb/s)
Medium Data Rate
Voice and Low Data
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(eg 144kb/s)
Rate (eg up to 64kb/s)
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 3
Cell Breathing
Multiservice Environment
Coverage for each
service is traffic
dependent
è Cell shrinkage
Seamless Coverage
100 subs/km2 - Year 1
300 subs/km2 - Year 3
Service Coverage:
Blue: Voice Only
w Green: Voice and CS64
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 4
w Red: Voice, CS 64 and PS384
w
All rights reserved © 2002, Alcatel
1000 subs/km2 - Year 5
From traffic forecast to coverage prediction
Iterative Link Budget Dimensioning
Multiservice Traffic
inputs
W-CDMA
Radio Parameters
ge
e
ng
Ran
Ra
Cellll Ra
e
ng
Ce
on
pti
um
sum
ass
as
umption
ass
Interference
TRAFFIC ANALYSIS
ANALYSIS
TRAFFIC
LINKBUDGET
BUDGETANALYSIS
ANALYSIS
LINK
Iterative process
until convergence
UL
traffic
DL
traffic
UL
analysis
DL
analysis
Final
Final
UL
UL&&DL
DL
Cell
Cell
Range
Range
UL & DL Cell range
> Use of Multiservice traffic modelling and iterative interference calculation
in both uplink and downlink to get the evolution of the cell range
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 5
All rights reserved © 2002, Alcatel
Strategic cell radius
Fixing a time variant parameter
>
Strategic cell
Dense Urban / Cell range = f(Phases)
range will define
Voice with 1 carrier
Cell range (km)
the deployed
inter-site
distance per
environment
¤Site
¤Site
¤Site
0.65
Seamless coverage
0.6
R
1.5x
Traffic increases
¤Site
Site
Site
¤
¤
¤Site
Holes in
coverage
Example of
strategic cell radius
0.55
PHO
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 6
PH1
PH2
Phases
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PH3
Advanced Features
Avoiding Cell Breathing problems by timely upgrade
t
t
>
Anticipate holes through coverage prediction
>
Avoid holes by timely upgrade
In
In case
case of
of Downlink
Downlink limitation
limitation
ww TX
TX Diversity
Diversity
ww High
High power
power amplifier
amplifier
t
tFor
For either
either Uplink
Uplink or
or Downlink
Downlink
limitation:
limitation:
t
t In
In case
case of
of Uplink
Uplink limitation
limitation
ww Tower
Tower Mounted
Mounted Amplifier
Amplifier (TMA)
(TMA)
ww 4
4 Way
Way RX
RX Diversity
Diversity
ww Multi
Multi User
User Detection,
Detection, MUD
MUD
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 7
ww Adding
Adding carriers
carriers
ww Sectorisation
Sectorisation
ww Adding
Adding sites
sites (densification)
(densification)
ww Smart
Smart antennas
antennas
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Tower Mounted Amplifier
Uplink Coverage Gain
18
Antenna
TMA
Tx
Rx
Duplexer
Feeder
Tx / Rx
Total Interference I (dB)
Duplexer
16
Link Budget Curve with TMA
Link Budget Curve w/o TMA
I(R) for High_Traffic
I(R) for Low_Traffic
14
12
10
Typical reduction of the required number
of sites:
8
~40% for low traffic scenario
– ~30% for high traffic scenario
–
6
4
2
Node B
0
0
0.2
0.4
0.6
Cell Range R (km)
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 8
0.8
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1
4-RX diversity on Uplink
Uplink Coverage Gain
10
Polarisation Space
Diversity Diversity
9
Total Interference I (dB)
8
7
Distance d
Xpol
antenna 1
6
Polarisation
Diversity
Xpol
antenna 2
5
4
Rxdiv1 Rxdiv2
Rxdiv3
Rxdiv4
3
Typical reduction of the required number
2
of sites:
~30% for low traffic scenario
– ~40% for high traffic scenario
–
1
0
0
0,2
0,4
Cell Range R (km)
0,6
Link Budget Curve w/o 4RxDiv
I(R) for High_Traffic w/o 4RxDiv
I(R) for Low_Traffic w/o 4RxDiv
Link Budget Curve with 4RxDiv
I(R) for High_Traffic with 4RxDiv
I(R) for Low_Traffic with 4RxDiv
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 9
All rights reserved © 2002, Alcatel
High Power Amplifier
Impact of Node B power on DL capacity
Transmit power
(Watt)
per carrier
Transmit
power (Watt)
45
40
35
RURAL 7 km
30
>
Negligible
impact in urban
areas
>
Visible gain only
in low density
rural areas
RURAL 5 km
SUBURBAN 1,3 km
25
URBAN 0,5 km
URBAN DENSE 0,35 km
20
Capacity
gain
15
Rural
10
5
0
100
Urban
200
300
400
500
600
700
800
900
Throughput NRT 128 (kbps)
Sector
Capacity
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 10
All rights reserved © 2002, Alcatel
High Power Amplifier
DL Gain in multicarrier configurations - Urban
20W vs. 35W at antenna connector: NRT 128 in Urban
50%
From 6.7W per carrier to
11.7W per carrier (3 carriers)
Capacity gain (%)
40%
From 10W per carrier to 17.5W
per carrier (2 carriers)
30%
Uplink
Coverage
limited cell
ranges
From 20W per carrier to 35W
per carrier (1 carrier)
20%
small gain for 3 carriers
10%
negligible gain for 1 carrier
0%
0
0.1
0.2
0.3
0.4
0.5
0.6
Cell range (km)
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 11
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0.7
0.8
TX Diversity on Downlink
Performance Gain
TX Bus
>
Power Amplifier
Performance gain of TX diversity
feature consists of three aspects:
¶
TX1
PA
Antenna
20 W
Antenna 1
TEU
Doubling the TX power by adding a
TX1div
power amplifier
PA
20 W
Antenna 2
TEU
Reducing the required transmit power
for each downlink channel (transmit
power raise due to fast fading is
reduced)
¸
Improving the required received Eb/N0
(slight reduction for open loop
TxDiv, higher for closed loop TxDiv)
Speech 8 kbps, 1 rx antenna, downlink, pedestrian A
9
Target Rx Eb/N0 (dB)
·
0.8 dB
8
7
6
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 12
Without Tx diversity
STTD
3
6
10
25
Speed (km/h)
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50
120
TX Diversity on Downlink
Gain on Downlink Capacity - Example
>
Gain highly dependent on diversity technique (open or closed loop)
and multipath profile (Pedestrian>>Vehicular)
Capacity gain by doubling the max. downlink
transmit power (%)
Example:
STTD - Space-Time transmit diversity (open loop)
Vehicular A, NRT 128, Urban,
20%
18%
16%
From(20W,1Carrier)
To (40W,1Carrier)
14%
Uplink
Coverage
limited
cell
ranges
12%
10%
8%
•
Pure Diversity gain in capacity: ~8%
•
Gain through 2nd PA:
dependent on cell range (curve)
6%
Example for typical cell range
(0.55km):
4%
2%
0%
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
8%+3%=11% total gain
Cell range (km)
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 13
All rights reserved © 2002, Alcatel
Adding a carrier
Uplink coverage
16
>
Total Interference I (dB)
14
12
Uplink Coverage:
•
10
8
6
link budget curve
I(Traffic),1 carrier
I(Traffic), 2 Carriers
4
2
Link Budget curve
stays the same, traffic
curve depends on #
of carriers
0
0
0.1
0.2
0.3
0.4
Cell Range R (km)
0.5
0.6
0.7
UL Coverage gain
Low traffic
High traffic
Carrier config
Dense Urban
Rural
Dense Urban
Rural
1C -> 2C
5%
10%
20%
20%
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 14
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2C -> 3C
3%
5%
15%
15%
Adding a carrier
Downlink capacity
t
Significant increase of downlink capacity
t
Exact gain depends on the hardware configuration (Nb of PA per
sector, # of carriers, etc…) and cell range
t
Carrier
TX
C1
Adding a carrier implies:
reducing power per carrier
(20W Ü 2x10W)
C2
Power Amplifier
PA
Antenna
Antenna 1
10 W per carrier
100%
Capacity gain (%)
75%
t
Uplink
Uplink
Coverage
Coverage
limited
cell
limited cell
ranges
ranges
50%
Adding a carrier is not only a
downlink feature, but will bring
for fixed intersite distance
uplink capacity gain as well
25%
From 1 carrier (20W p.c.)
to 2 carriers (10W p.c.)
Most powerful enhancement
From 2 carriers (10W p.c.)
to 3 carriers (6W p.c.)
feature
0%
0
How to minimize
the impact of 0.2
cell breathing effect 0.4
on UMTS network / 0.6
July 4th / 15
Cell range (km)
0.8
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Deployment strategy
Incumbent Operator
GSM
GSM Cell
Cell range=strategic
range=strategic cell
cell radius
radius
Start: Phase 0
Coverage and Capacity analysis
Traffic forecast
NO
Holes or capacity problems?
Look at
next phase
YES
Which limitation?
UL
DL
Apply UL feature
(TMA, 4RXDiv, MUD)
(if not yet used)
Apply DL feature
(TxDiv, HPA)
(if not yet used)
both UL&DL
Add a carrier
(if still available)
Maximize the re-use of existing GSM sites
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 16
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Deployment strategy
Greenfield Operator
Evaluate Cell Ranges
(for all traffic phases and scenarios)
Identify suitable strategic
ranges
Apply possible deployment
scenarios
(service deployment,
advanced features upgrade)
There is no unique solution
for strategic cell range and
deployment strategy, the final
choice is an (individual)
strategic decision!
Build business cases
Select the solution that best fits
your business requirements
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 17
All rights reserved © 2002, Alcatel
Conclusion
>
Analytical dimensioning techniques can be used for
predicting and avoiding potential problems due to cell
breathing (Ü upgrade strategy)
>
The network evolution can be considered already at
dimensioning stage
>
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
How to minimize the impact of cell breathing effect on UMTS network / July 4th / 18
All rights reserved © 2002, Alcatel
Thank you for your attention
Yannick DUPUCH
UMTS Project Manager
Mobile Networks Division
[email protected]