02 - 2006-02-10_Digitel - Air Interface Dimensioning

All rights reserved © 2006, Alcatel

Digitel/Alcatel – Air Interface Dimensioning

2006, February 10thNathalie PEYROT

All rights reserved © 2006, AlcatelDigitel 3G Workshop / February 2006

Derive Cell size ( <=> Cell range)

Define Site configuration Number of sectors/ antennas Number of carriers Antenna height Number of Boards

Choose Radio Feature to increase Cell capacity to improve Cell coverage

Forecast Network Evolution

Antenna 1 Antenna 2

Cell Dimensioning Purposes

To meet Operator’s targeted GoS and QoSTo meet Operator’s targeted GoS and QoS


UTRAN dimensioning / Agenda

Challenges of UMTS Cell Dimensioning a new technology: W-CDMA Multi-Service traffic environment Coverage Capacity Trade-off

Air Interface Dimensioning


What is going to impact Cell Dimensioning in UMTS?

1°) A New Technology: W-CDMA

Interference limitedInterference limited

Frequency reuse of 1Frequency reuse of 1

Power controlPower control

Soft HandoverSoft Handover

Cell BreathingCell Breathing


What is going to impact Cell Dimensioning in UMTS?

2°) A Multi-service traffic environment Various Data Rates (from speech 12.2 kbps to 384 kbps)

Various QoS & GoS (Blocking, delay, throughput, BLER)

Various Connection type (Real Time (CS) or Non Real Time (PS))

Various Traffic asymmetry and behaviour

Different sensitivitiesDifferent sensitivities

Different FootprintsDifferent Footprints Speech 12.2 kbpsNRT 128 kbps

NRT 384 kbps


Coverage and Capacity Trade-off

Multi-service Traffic

in the cell

Multi-service Traffic

in the cellCell RangeCell Range

InterferenceInterference

Need of an

iterative process

between

traffic analysis

&

link budget analysis

Need of an

iterative process

between

traffic analysis

&

link budget analysis

Understanding the network behaviour

allows a better tailored network


Multi-service Link Budget

Multi-service Traffic ModelingMulti-service Traffic Modeling

WCDMAWCDMAMULTISERVICE Traffic MULTISERVICE Traffic

Need for a W-CDMA LKB(Cell load, Eb/N0, SHO gain…)

Different Footprints Cell breathing

Need for a Continuous coverage

Multi-service W-CDMA LKBMulti-service W-CDMA LKB


Do we have another solution?

To avoid Complexity of traffic modelling and DL power analysis?

Rollout Phases

Phase 1 Phase 2 Phase 3 Phase 4

515

500

475

450

425

400

Feature addingFixed Cell loadReal Cell Range

Cell R

an

ge (

m)

Network Sized by Fixing Cell load to an arbitrary constant value (e.g. 50% = 3dB) in UL

Does not Reflect real Network Evolution, does not run Traffic

forecastsDoesn’t allow to set up

optimised and customised Network deployment

strategy

Coverage Holes

Therefore, Iterative Multi-service Link Budget is required


Iterative Multi-service Link Budget

WCDMA Radio ParametersWCDMA Radio Parameters

MULTISERVICE Traffic MULTISERVICE Traffic

UPLINK AnalysisUPLINK Analysis

DOWNLINK Analysis

DOWNLINK AnalysisTraffic

ModelTraffic Model

Iterative

Process

Iterative

Process

UL cell range DL cell range

Interference Interference &Power

UL Cell rangeMobiles Tx PowerUL cell loadUL Capacity


DL Cell rangeNode-B Tx PowerDL cell loadDL Capacity


BalancedCell Range



Challenges of UMTS Cell Dimensioning

Air Interface Dimensioning Traffic Modelling in UMTS Uplink Analysis Downlink Analysis


Traffic Modelling Purpose

Purpose: Dimension the different Node-B

resources in order to handle the peak of traffic and meet the GoS requirements.

Inputs Traffic Inputs provided by the Operator WCDMA Parameters Other

Means Mathematical laws Equations, Algorithms

Traffic ModelTraffic Model

Busy hour

Required Resource

Cell RangeNumber of

carriersFeatures

Number of services / SubscribersService bit rate ; Traffic volume Blocking / delay

Number of services / SubscribersService bit rate ; Traffic volume Blocking / delay

Eb/No, Chip Rate, Processing gain, Soft Handover...

Eb/No, Chip Rate, Processing gain, Soft Handover...

Traffic Model

Traffic Model

Inputs

InterferenceNode-B PowerNumber of Base Band BoardsIub interface size

C

c

c

C

block

!c

!CC,EP

0


Traffic Modelling Example: GSM

Purpose: For considered example (GSM):

Derive the required number of TRXs

Inputs Traffic in Erlangs, Blocking rate

Means Erlang B law

E.g: One TRX with 7 traffic channels can handle 2.9 Erl @ 2% blocking


C

c

c

C

block

!c

!CC,EP

0

Subscriber 1

Subscriber 2

Subscriber 3

Subscriber 4

Observation Time (1H)

Call Setup

Blocked

Call Release

Peak Traffic OccurringReserved Capacity @ BTSMean Traffic Occurring

Capacity Demand


Traffic Modelling in UMTSChallenges

Recurrent issues in UMTS dimensioning: Sharing a resource between different users How to model multi-service traffic behaviour on Air Interface How to play on different GoS requirements Derive the required capacity, but optimised


Average traffic

Busy hourCombination of 1 user128K +3 voice users+1 user 64K

Over-Dimensioning

OptimisedDimensioning

Under-dimensioning

Voice, SMS,

Video conferencing,

Shopping on line,

Web browsing,

File transfer,

Video games...

Aggregate traffic


Traffic Modelling in UMTSExample of Traffic Inputs

Subscriber density: 4670 subs/km²data Traffic per sub: 2,071 MbitsCell range: 400m


Service Class BHCA UL Bit rate DL Bit rate mErlangs Callduration

Messagelength

Voice Conversational 2 12.2 Kbps 12.2 Kbps 50

SMS Background 0.5 32 Kbps 32 Kbps

MMS Background 0.02 32 Kbps 32 Kbps 40 Kbytes

Streaming Video Streaming 0.04 64 Kbps 128 Kbps 5 Mbytes

Streaming Audio Streaming 0.04 64 Kbps 128 Kbps 1.2 Mbytes

Video telephony Conversational 0.03 64 Kbps 64 Kbps 0.5

Video conference Conversational 0.01 128 Kbps 128 Kbps 1.7

Web Browsing Veloce Interactive 0.04 64 Kbps 128 Kbps50 mn(10%)

Web Browsing lento Background 0.04 32 Kbps 32 Kbps100 mn(10%)

Service UL Bit rate DL Bit rate Percentage

CS 64 64 Kbps 64 Kbps 1%

PS 32 32 Kbps 32 Kbps 29%

PS 64 64 Kbps 128 Kbps 67%

PS 128 128 Kbps 128 Kbps 3%

Service Unit Total volume

Speech Erl 24.3

CS 64 Mbits 10

PS 32 Mbits 292

PS 64 Mbits 674

PS 128 Mbits 30

Traffic per sector @ BH


Traffic Modelling in UMTSWrong Approach 1: Mono-service Erlang-B Traffic

ModelTraffic Model


Speech Erl 24.3

CS 64 Mbits 10

PS 32 Mbits 292

PS 64 Mbits 674

PS 128 Mbits 30


Estimation of peak DL throughput (Kbps) per sector:

Results with a Mono-service Erlang-B approach:

Erlang-B applied to each service with 2% blocking

# channels

33

2

7

7

2

Multiply by each bit rate

Throughput

402.6

128

224

448

256

Total Throughput on sector:1458.6 Kbps

Wrong Approach: No resource sharing -> No spectrum Efficiency -> Over-

dimensionedBad handling of packet calls (not blocked)Does not reflect occurring traffic behaviour


Traffic Modelling in UMTSWrong Approach 2: Average Traffic



Speech Erl 24.3

CS 64 Mbits 10

PS 32 Mbits 292

PS 64 Mbits 674

PS 128 Mbits 30



Results with an Average Traffic approach:Average Throughput

148.2

2.8

81

187.2

8.3

Total Throughput on sector:427.5 Kbps

Wrong Approach: Under-dimensioned Target GoS not achieved (to much blocking)


Traffic Modelling in UMTSFirst Improvement: Knapsack (1/7)

The issue resides in the computation of the shared system capacity knowing GoS requirements (blocking probability, delay) the shared capacity can be an interference, a number of radio

resources, a transmit power, a throughput…

Few models dealing with resources shared by various services can be found in the literature The knapsack model (also called Multi Erlang) gives an

analytical solution for CS-services


Time


Analytical tool running Enhanced Knapsack


Time

Circuits services (voice and streaming)

Interactive packets services (web browsing)

Background packets services (mail)

Cap

acit

y

Busy Hour

Resource

Computation of a shared resource (by all PS and CS services): Cell load for the Uplink Power for the Downlink Throughput (Kbps)

Respects QoS and GoS

Traffic Modelling in UMTS Second Improvement: Alcatel Traffic Model



Results with a Multi-service Enhanced Knapsack approach:

Traffic Modelling in UMTS Second Improvement: Alcatel Traffic Model Traffic

ModelTraffic Model


Speech Erl 24.3

CS 64 Mbits 10

PS 32 Mbits 292

PS 64 Mbits 674

PS 128 Mbits 30


Total Throughput on sector:829 Kbps

Optimised Approach:Optimised dimensioning -> reflects more real traffic

occurringTarget GoS achieved for every serviceMulti-service Traffic Model for shared resource

computation



Over dimensioning methods

Traffic Modelling in UMTS Comparison of the different approaches Traffic

ModelTraffic Model

Summary :

Under dimensioning method

0

200

400

600

800

1000

1200

1400

1600

Peak T

hro

ughput

(kbps)

AverageTraffic

ALCATEL Knapsackwith equalGoS for CS

and PS

Erlang-B&CSum

Erlang-Bsum

Comparison of the different traffic modelling approaches

OPTIMIZED

DIMENSIONING


Traffic Modelling in UMTSConclusion

Traffic Modelling is used for Node-B dimensioning Purpose: Find the appropriate capacities for the different Node-

B resources in order to handle a peak of traffic and meet the GoS requirements

Mono-service law like Erlang-B is not appropriate: => leads to over-dimensioning

Need for a Multi-service Traffic Model Resources are shared

Has to handle CS and PS Grade of Service Has to reflect real traffic occurring in the cell to better anticipate coverage&capacity issues



Traffic Modelling in UMTSCS Input Parameters Traffic

ModelTraffic Model

Bit rate User bit rate for the circuit connection

QoS and Radioquality

BLER and associated Eb/N0 [dB] per multipathenvironment for uplink

BLER and associated Eb/N0 [dB] per multipathenvironment for downlink

GoS Maximum acceptable Blocking Percentage

Traffic ModellingParameter

Activity Factor for uplink

Activity Factor for downlink

Number of subscribers N per sqkm and trafficintensity ‘ per subscriber (in mErlang)


Traffic Modelling in UMTSPS Input Parameters Traffic

ModelTraffic Model

Uplink: Mean User bit rate and Peak User bit rateBit rate

Downlink: Mean User bit rate and Peak User bit rate

Uplink: BLER and associated Eb/N0 [dB] per multipath environmentQoS andRadio quality

Downlink BLER and associated Eb/N0 [dB] per multipath environment

Uplink: acceptable maximum delay time dULx% and quantile x%

(in x% of the cases, the delay has to be lower than or equal to dx%.)

GoS

Downlink acceptable maximum delay time dDLx% and quantile x%

(in x% of the cases, the delay has to be lower than or equal to dx%.)

Uplink Data Volume per busy hour V (in kbit/busy hour) per subscriber

Downlink Data Volume per busy hour V (in kbit/busy hour) per subscriber

TrafficModellingParameter

Number of subscriber N per sqkm






Uplink Analysis Main Characteristics


KTB

Transmit PowerP1

Transmit PowerP2

Transmit PowerP3

Transmit PowerPi

Total Interference @ Node-B

Interference Perceived by user 1

Mobiles transmit on same frequency simultaneously

Asynchronous Other UEs interfere System is interference limited

According to Power Control instructions, Mobiles adjust their power to:

Achieve target C/I Overcome Pathloss (impacted by distance) Overcome Interference (impacted by Traffic)

Interference (Iintra and Iextra) is independent of UEs’ locations


Link Budget is performed for one mobile located at cell edge (for each service) transmitting at max power

The interference (Intra-cell and extra-cell) perceived by this UE is calculated @ Node-B, including the entire traffic mix (Traffic Model)

Interference is a shared resource

Uplink Analysis Main Concepts


cell radius

MAPL

Required Received Signal

Max UE transmit Power

UPLINK Analysis is an MAPL analysis

UPLINK Analysis is an MAPL analysis


UL link budget elaborated for user of service k at cell edge transmitting at maximum power

cell radius

Maximum Allowable Pathloss

Reference Sensitivity

Max UE transmit Power

Gains - Losses- Margins

Interference marginintra and extra cell interference Reference

SensitivityReference Sensitivity

Transmit PowerTransmit Power

Losses and Margins

Losses and Margins

GainsGains

= MAPL

Uplink Analysis MAPL Calculation


InterferenceInterference


Uplink Analysis MAPL Calculation / Example


W-CDMA Specific ParametersEffective Chip Rate 3840 KcpsService Bit Rate 64 KbpsProcessing Gain 17.8 dBTarget Eb/No 3.1 dBUL f ( Iintra/Iextra) 0.84

MS TransmitterTX power 21 dBm

Node-B ReceiverRX Antenna Gain 17 dBiCable and Connector losses 3 dBReceiver Noise Figure 4 dBThermal Noise -174 dBm/HzReceiver sensitivity (dBm) (to be calculated from above figures)

Gains & MarginsShadowing Margin 4.8 dBUL Rayleigh Margin 1.7 dBPenetration Margin 20 dBBody Loss 0 dB

Interference MarginInterference Margin (dB) Either fixed (e.g. 3dB) or calculated from Traffic Mix

Cell RangeMAPL (dB) (to be calculated from above figures)Cell Range (km) (to be calculated from above figures)

Example of a Mono-service UL UMTS FDD Link Budget

Service: PS 64 Kbps

Mobile Power: 21 dBm


Rx Sensitivity calculation (for service k) : Minimum required level to reach a given quality

(C/I target) when facing only thermal noise

Where:

Nth Thermal Noise density, 10log(Nth) =-174 dBm/Hz

(Eb/N0)k : Service k target Eb/No

Rk: Service k bit rate

NF: Node-B Noise figure in dB

Reference Sensitivity = (C/I) k+NF + 10log(NthW)

and (C/I) k= (Eb/N0)k - PG

= NF +10log(Nth)+ (Eb/N0)k + 10log(Rk)

Service dependent

in dBm

in dB

Uplink Analysis MAPL Calculation / Example / Receiver Sensitivity



Uplink Analysis MAPL Calculation / Example / Receiver sensitivity




Node-B ReceiverRX Antenna Gain 17 dBiCable and Connector losses 3 dBReceiver Noise Figure 4 dBThermal Noise -174 dBm/HzReceiver sensitivity (dBm) -118 dBm




Receiver Sensitivity Calculation:

Rx = 3.1 + 4 - 174 +48 Rx = -118.8 dBm

How are these margins calculated ?


Due to Reflection and diffraction of the transmit signal on obstacle there is not only one path but a large number of paths with different delays and amplitudes

Slow fading variations due to obstacles are called shadowing

Shadowing can be modelled as a random variable with log-normal distribution of 0 mean and standard deviation that is characteristic of the environment

Uplink Analysis MAPL Calculation / Example / Shadowing Margin



Shadowing impact on the coverage is taken into account through a “shadowing margin” in the link budget=> UE must increase their power to compensate for the shadowing anywhere in the cell

It is computed as in GSM : in a single cell

It is computed such that the average probability that this margin be exceeded in the cell is below a certain threshold => 5 to 10%




When a UE is at cell edge, there is a significant probability that it is in soft-handover.

Since the shadowing is partially uncorrelated between the different radio links, SHO enables to decrease the shadowing margin.

This performance gain comes from the fact that it is more unlikely to have a large attenuation for all links at the same time than for only one single link.

BS1 BS2

Same carrier




Depending on Shadowing standard deviation Area coverage probability Pathloss exponent K2 (Hata: K1+K2log R) Number of SHO legs

UL Shadowing margin (dB)(no SHO)

UL Shadowing margin (dB)(SHO, 2 legs)

Areacoverage

probability = 6 = 8 = 12 = 6 = 8 = 1295 % 5.9 8.7 14.6 3.1 4.8 8.5

90 % 3.3 5.4 10.0 0.6 2.1 6.4

-8

-4

0

4

8

12

16

0 5 10 15 20 25 30

Average outage probability (%)

Shadow

ing m

arg

in (dB)




In Uplink:Gain on shadowing marginnegligible gain on required

Eb/N0 (~0.2dB)=> slight improvement

Soft-handover gain (dB)Outage probability = 4 = 6 = 8 = 10 = 12

1 % 2.2 3.3 4.5 5.7 6.95 % 1.9 2.9 3.9 5.0 6.0

10 % 1.7 2.7 3.6 4.6 5.6

RNC

Node-BNode-B

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

0 5 10 15 20 25 30


Soft

-handover

gain

(dB

) Soft-handover gain, rho=0

Soft-handover gain, rho = 0.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

0 5 10 15 20 25 30


Soft

-handover

gain

(dB



Uplink Analysis Power Calculation / Example / Soft Handover



Due to Reflection and diffraction of the transmit

signal on obstacles there is not only one path but a

large number of paths with different delays and

amplitudes

Each main path is a superposition of multiple paths

that are very close to each other which implies

that its amplitude is Rayleigh distributed This effect is known as Rayleigh or Fast fading

Uplink Analysis MAPL Calculation / Example / Fast Fading



Impact of power

control:

Fight the fading

dips

For slow-moving

mobiles, Power

control is efficient

and will

compensate the

fading-20

-15

-10

-5

0

5

10

15

20

25

0 1000 2000 3000

Slot Number (0,666 ms)

Po

wer

(d

Bm

)F

ast

fad

ing

val

ues

(d

B)

Fast fading samples (dB)

Transmit power (dBm)

0 1000 2000 3000

Slot Number (0,666 ms)

Received

P

ow

er at N

od

e-B

(d

Bm

)




When the UE is near the cell edge, it may not be able to increase its transmit power to compensate for fast fading : the transmit power is limited by the maximal UE transmit power (typically 21 or 24 dBm) Power control is not anymore efficient at cell edge : the

performance at cell edge becomes close to the one without power control

It implies a margin has to be taken into account in the link budget to compensate for the power control degradation at cell edge : this is the fast fading margin




In a single cell : difference between the required Eb/No with and without power control

However at cell edge the mobile station will be in Soft-Handoff

The UE will be power controlled by the best received cell

The selection combining of the different radio links of the active

set enables to decrease the received power variation and thus

SHO enables to decrease the fast fading margin

on PC0

b

off PC0

b

N

ERx

N

ERxg_marginFast_fadin




For medium to high speeds the For medium to high speeds the

margin margin is equal to zerois equal to zero because because

the the power control is no more efficientpower control is no more efficient

For medium to high speeds the For medium to high speeds the

margin margin is equal to zerois equal to zero because because

the the power control is no more efficientpower control is no more efficient

FAST FADING MARGIN (DB)FOR SEVERAL TARGET BLERMorpho-structure

10-1 10-2 10-3 10-4

VEHICULAR A 3KM/H

(DENSE URBAN,URBAN, SUBURBAN)

0.6 1.7 2.5 3.3

VEHICULAR A120KM/H

(RURAL)

0 0 0 0

Depending on

Channel model (Vehicular, Pedestrian)

Speed

BLER service target

0,0001

0,001

0,01

0,1

1

2 3 4 5 6 7 8

Required Eb/No (dB)

BL

ER

Without powercontrol

With powercontrol




Uplink Analysis MAPL Calculation / Example / Factor f








Other Important parameter:

Other Cell Interference Factor

Margins already include SHO gain


Other Cell Interference Factor (OCIF) is defined as

f is derived from System Level simulations Values are depending on parameters such as: Environment (dense urban, urban…)

propagation Pathloss coefficient shadowing standard deviation

Fast fading Soft-handover conditions Sectorization

Impact on capacity and cell load calculations

intra

Iextra

I f

Uplink Analysis MAPL Calculation / Example / Factor f


OTHER-CELL INTERFERENCE FACTORMorpho-structure

= 4 = 6 = 8 = 10 = 12

DENSE URBAN 0.69 0.78 0.84 0.87 0.93

URBAN 0.69 0.78 0.84 0.87 0.93

SUBURBAN 0.71 0.79 0.86 0.89 0.95

RURAL 0.70 0.89 0.89 0.93 1.00


Uplink Analysis MAPL Calculation / Example / Interference








How to assess Interference Margin


Interference level as a function of capacity

0

5

10

15

20

25

30

35

0 11 21 31 41 51 61 71 81 91 100

Cell loading (%)

50% of cell load

(3dB of interference)

max loading : 75%

Interferen

ce level (dB)

By definition, cell load and total interference rise (“noise rise”) are linked:

ULo

totaldBtot x

WN

Ii

1log10log10_

where Itotal is the total received power at the node B (including the useful signal Ck )

The interference rise includes the useful signal

it is not the noise rise perceived by a user !




The interference rise perceived by a user of service k to be added to the MAPL calculation is then equal to :

kdBtotodB ii _

k is negligible for low data rate services, but significant for high data rate services!

UL cell load,depend on number of users in the cell


kUL

ktotal

total

o

total

o

ktotaldB

I

Clogxlog

CI

Ilog

WN

Ilog

WN

CIlogi

110110

1010100


Numerical Example

for a PS 64 user in a cell loaded at 50%:

i = 3dB - 0.14dB = 2.86 dB








Interference MarginInterference Margin (dB) 2.86 dB

Cell RangeMAPL (dB) 124.5 dBCell Range (km) 330 m

In Mono-service with a fixed cell load of 50%, the noise rise perceived by the considered UE:

i = 3dB - 0.14 dB = 2.86 dB

As a result:

MAPL = 124.5 dB

Cell range = 330 mMono - Service LKB




In Multi-service:

Different Bit Rates

Different Eb/No

Different sensitivities

Different contributions to noise rise

Total interference calculated for all the subs and all services

Multi - Service LKB

W-CDMA Specific ParametersEffective Chip Rate 3840 Kcps 3840 Kcps 3840 KcpsService Bit Rate 12.2 Kbps 64 Kbps 128 KbpsProcessing Gain 25 dB 17.8 dB 14.8 dBTarget Eb/No 6.4 dB 3.1 dB 2.5 dBUL f ( Iintra/Iextra) 0.84 0.84 0.84

MS TransmitterTX power 21 dBm 21 dBm 21 dBm

Node-B ReceiverRX Antenna Gain 17 dBi 17 dBi 17 dBiCable and Connector losses 3 dB 3 dB 3 dBReceiver Noise Figure 4 dB 4 dB 4 dBThermal Noise -174 dBm/Hz -174 dBm/Hz -174 dBm/HzReceiver sensitivity (dBm) -122.7 dBm -118 dBm -116.4 dBm

Gains & MarginsShadowing Margin 4.8 dB 4.8 dB 4.8 dBUL Rayleigh Margin 1.7 dB 1.7 dB 1.7 dBPenetration Margin 20 dB 20 dB 20 dBBody Loss 3 dB 0 dB 0 dB

Interference MarginI perceived by 1 UE (dB) 2.94 dB 2.86 dB 2.75 dBTotal Interference (dB) 3 dB

Cell RangeMAPL (dB) 122 dBCell Range (km) 283 m



Assuming perfect power control and uniform cell loading

Uplink AnalysisRelation between the number of users and the cell load

servN

jtotal

jIC

jIC

jratotaljI

C

jIC

kktotal

k

k

INIICCI

C

I

C

1int .

1..

1

raextra IfI int.

UL

erratotal

x

WN

IINI

1

. 0

intint0

servN

j jIC

jIC

jUL Nfx1 1

..1

f=OCIF factor

Note: C/I in non-logarithmic values

Multi - Service Cell Load


Cell Load is a resource shared by all users in the cell.

Derive Peak Cell Load: Each user has a different contribution to cell load depending on its service (bit rate, QoS, CS or PS)

Uplink AnalysisPeak cell load calculation


servN

j jIC

jIC

jUL Nfx1 1

..1


xUL

The cell load the Cell has to be

dimensioned for


Cell Load is a resource shared by all users in the cell.

Uplink AnalysisPeak cell load calculation / Example


servN

j jIC

jIC

jUL Nfx1 1

..1

XUL = 51.6%

(2 carriers)



Service C/I/(1+C/I) Total volume

Speech 0.014 24.3 Erl

CS 64 0.042 10 Mbits

PS 32 0.018 292 Mbits

PS 64 0.033 674 Mbits

PS 128 0.056 30 Mbits

KTB

Received signal 384 kbpsReceived signal 128 kbpsReceived signal Speech

Interference

Total throughput: 524 kbpsTotal throughput: 292 kbps

Received signals @ Node-B



Assume an interference level of

I0

Assume an interference level of

I0Compute cell range through link budget

calculation

Compute cell range through link budget

calculation

Apply Traffic Model to captured traffic with this cell range :

deduce Icalc

Apply Traffic Model to captured traffic with this cell range :

deduce Icalc

Icalc = I0 ?

Icalc = I0 ?

UL RadiusUL Radius

Yes

No, adjust IoTraffic ModelTraffic Model

limiting one of all services radii

knowing nb of sub/sqkm per serviceand the QoS required per service

Uplink AnalysisMain Process


Multi-service Link Budget is required in UMTS for Uplink Analysis

Uplink Analysis is a conventional MAPL analysis Link Budget is performed for one user of each service located at cell edge

Interference perceived by this user is generated by all the mobiles in the cell and all the services

The shared resource in Uplink is the Interference (related to cell loading)

The peak interference is calculated with a multi-service traffic model

Uplink AnalysisConclusion



Uplink AnalysisRequired Parameters


Traffic Parameters Services, service class, bit rates, traffic volumes,

GoS Allowed blocking and delay

QoS and Radio Quality BLER and associated Eb/No, Noise Figure

Coverage Requirements Land Usage (Clutter Information), Penetration lossper clutter, Coverage Probability

Subscriber density Subs density per clutter, traffic maps

W-CDMA parameters Available frequencies, chip rate, Other CellInterference Factor, Multipath environemnt(Vehicular A3km/h, Pedestrian…)

Radio Parameters Margins (Shadowing, Fast Fading, Body-loss),Gains (antenna, SHO), Propagation Model

Site configuration Antenna height, cable losses






Downlink Analysis Main Characteristics

DOWNLINK Analysis

DOWNLINK Analysis

User 1

Total PowerTransmitted by Node-B

Power share dedicated to user i

User 2

User 3

User i

Node-B transmits simultaneously, on the same frequency, towards all mobiles

Power is shared by all the users, and has to satisfy all traffic in the cell

Mobiles Position and traffic will impact both: Node-B Power Interference

System is both Interference and Power limited


DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Main Concepts

Link Budget is performed for all mobiles distributed in the cell (uniformly) and all services

Values of required receive signal are calculated for all positions, taking into account SHO probability, OCIF value and Pathloss

Power and Interference are shared resources determined with the traffic model

DOWNLINK Analysis is a Power analysis

DOWNLINK Analysis is a Power analysis

0,0000

0,2000

0,4000

0,6000

0,8000

1,0000

1,2000

1,4000

1,6000

1,8000

0% 20% 40% 60% 80% 100% 120%

Distance compared to the cell radius (r/R)

fact

or

f Sigma 2dB

Sigma 4dB

Sigma 6dB

sigma 8dB

0,0000

0,2000

0,4000

0,6000

0,8000

1,0000

1,2000

1,4000

1,6000

1,8000

0% 20% 40% 60% 80% 100% 120%


fact

or

f Sigma 2dB

Sigma 4dB

Sigma 6dB

sigma 8dB

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5

Probability that cell is in theactive set

Probability that cell is the onlylink

Probability of SHO and that cellis the best cell

Probability of SHO and that cellis a secondary cell

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5





Interference

SHO


DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Main Concepts

Required power calculations are performed by considering:

Mobiles suffering different path-losses (different users’ locations)

Mobiles requiring different radio quality values

(Eb/No, handover states,…)

Location dependency of factor f (ratio

between extra and intra-cell interference)

Mobiles that are not physically located

in the cell but requiring power

Power for common channels

Penetration margins and shadowing impact

Probabilistic traffic behaviour

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5





0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5





Interference from other cells

0,0000

0,2000

0,4000

0,6000

0,8000

1,0000

1,2000

1,4000

1,6000

1,8000

0% 20% 40% 60% 80% 100% 120%


facto

r f Sigma 2dB

Sigma 4dB

Sigma 6dB

sigma 8dB

0,0000

0,2000

0,4000

0,6000

0,8000

1,0000

1,2000

1,4000

1,6000

1,8000

0% 20% 40% 60% 80% 100% 120%


facto

r f Sigma 2dB

Sigma 4dB

Sigma 6dB

sigma 8dB

SHO probability


How to assess Power ?

Consider one mobile located at distance d from Node-B

Puser 1(d)dBm = Attenuation(d)dB + Itot-user 1(d)dBm + (C/I)target,dB

DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Power Calculation / Example

Puser

1

Itot

Cuser 1Distance d

KTB


In Downlink NB has to compensate the channel variations for all UEs in the cell

The shadowing and Rayleigh margins are quite low (average at 2dB) since there is a very low probability that all UEs be in fading dip at the same time

One margin is taken to combine the two effects

Shadowing holesThe probability that a user at the other side of the cell faces hole of shadowing at the same time is very low

The probability that a user at the other side of the cell faces hole of shadowing at the same time is very low

A margin for each link is not realistic !

Downlink Analysis Power Calculation / Example / Shadowing Margin

DOWNLINK Analysis

DOWNLINK Analysis


Intra-cell Interference Iintra:

User 2

Extra-cell Interference Iextra:

User 3 + User 4 User 4

Itot-user 1(d) = N0.F.W + Iintra(d) + Iextra(d)

Downlink Analysis Power Calculation / Example / Interference

Total Interference Itot-user 1(d) perceived by User 1

User 1User 2

User 3

User 4


DOWNLINK Analysis

DOWNLINK Analysis


DOWNLINK Analysis

DOWNLINK Analysis


Intra-cell Interference Iintra(d)

Node-B transmits simultaneously, on the same frequency, towards all mobiles

At Node-B: Transmitted signals are orthogonal thanks to the use of channelization codes

User 1



User 2

User 3

User i


DOWNLINK Analysis

DOWNLINK Analysis


At Mobile: Due to Multipath and reflections, orthogonality is lost

After de-spreading, some intra-cell interference remains

Reflected by the Orthogonality Factor

User 1



User 2

User 3

User i

Delay 1

Intra-cell Interference

Delay 3


The Orthogonality Factor depends on the Multipath environment (Vehicular A, Pedestrian A)

It is computed through link level simulations On-Field estimation of Orthogonality Factor is on-going

Note the lower value (higher orthogonality) in Pedestrian A due to less multi-path

Environment Orthogonality factorPedestrian 0.06Vehicular 0.4


DOWNLINK Analysis

DOWNLINK Analysis


DOWNLINK Analysis

DOWNLINK Analysis


Intra-cell Interference Iintra(d) perceived by User 1:

Orthogonality Factor (E.g. 0,4)

Iintra(d)linear = .(Ptot - Puser 1(d)linear)/Attenuation(d)linear


DOWNLINK Analysis

DOWNLINK Analysis


Extra-cell Interference IExtra(d)

OCIF F is location dependent in Downlink: mobiles at cell edge receives more inter-cell interference than mobiles near their serving Node-B

As for Uplink, results are derived from system level simulations

0,0000

0,2000

0,4000

0,6000

0,8000

1,0000

1,2000

1,4000

1,6000

1,8000

0% 20% 40% 60% 80% 100% 120%


fact

or

f Sigma 2dB

Sigma 4dB

Sigma 6dB

sigma 8dB


DOWNLINK Analysis

DOWNLINK Analysis


Extra-cell Interference Iextra(d) perceived by User 1:

Other Cell Interference Factor (for Downlink)

IExtra(d)linear = F(d).Ptot/Attenuation(d)linear


DOWNLINK Analysis

DOWNLINK Analysis


So, Total Interference Itot-user 1(d) perceived by User 1

Itot-user 1(d) = N0.F.W + Iintra(d) + Iextra(d)

Itot-user 1(d) = N0.F.W + [.(Ptot - Puser 1(d)) + F(d).Ptot ]/Attenuation(d)

And Total Interference Itot(d)

Itot(d) = N0.F.W + [( + F(d)).Ptot ]/Attenuation(d)

Example, with: Node-B transmitting @ 43 dBm, attenuation of 129 dB, =0.4, F(d)=0.6 Itot(d)dBm = - 86 dBm


Finally, the expression of Puser 1(d) can be put under the form

Puser 1(d) = auser 1(d).Ptot+ buser 1(d)

Where,

auser 1(d) = (C/I)target/(1+(C/I)target).( + F(d))

buser 1(d) = (C/I)target/(1+(C/I)target)[N0.F.W.Attenuation(d)

Comments: One term to compensate for Interference (traffic) and one term to compensate for Propagation and Thermal Noise

Downlink Analysis Power Calculation / Example / Power

(C/I)target=(Eb/No) target /PG/SHO_gain

For user in SHO status


DOWNLINK Analysis

DOWNLINK Analysis


In Uplink:Gain on shadowing marginnegligible gain on required

Eb/N0 (~0.2dB)=> slight improvement

In Downlink: Gain on Eb/N0 : reduce the

Eb/No target of ~2.5dB (according to simulations)

Soft-handover gain (dB)Outage probability = 4 = 6 = 8 = 10 = 12

1 % 2.2 3.3 4.5 5.7 6.95 % 1.9 2.9 3.9 5.0 6.0

10 % 1.7 2.7 3.6 4.6 5.6

RNC

Node-BNode-B

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

0 5 10 15 20 25 30

Average outage probability (%)Soft

-handover

gain

(dB



3

3.5

4

4.5

5

5.5

6

6.5

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7.5

8

0 5 10 15 20 25 30

Average outage probability (%)Soft

-handover

gain

(dB



Downlink Analysis Power Calculation / Example / Soft Handover

DOWNLINK Analysis

DOWNLINK Analysis


DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Power Calculation / Example / Soft Handover

The required power depends on the Handover status of the UE:

Mobile linked to the Node-B, not in SHO

Mobile linked to the Node-B as best cell, in SHO

Mobile linked to the Node-B in secondary cell, in SHO

0

0.2

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Impact of User Position on Capacity

DL power is shared !

Node B Cell edge

0

Nu

mb

er

of

Users

50 100

DL Capacity = Function (UE distribution)

% Cell Range


DOWNLINK Analysis

DOWNLINK Analysis

Node-B power of 20W, 4W being allocated to Common Channels and 2 dB for shadowing

Users at 50% Cell Range: With 1006 mW per user, 9 PS 64 users can be supported Users at Cell Edge: With 1842 mW per user, only 5 PS 64 users can be supported

10 W


Three main solutions to compute the DL power

All users @ cell edgeAll users @ cell edge solution very pessimistic low capacity

All users @ cell edgeAll users @ cell edge solution very pessimistic low capacity

30% of mobiles @ cell edge and 30% of mobiles @ cell edge and 70% of UE @mid cell range70% of UE @mid cell range

Does not reflect the statistical behaviour of the cell and may lead to an under-dimensioninglow accuracy on capacity computation

30% of mobiles @ cell edge and 30% of mobiles @ cell edge and 70% of UE @mid cell range70% of UE @mid cell range

Does not reflect the statistical behaviour of the cell and may lead to an under-dimensioninglow accuracy on capacity computation

Uniform user distributionUniform user distribution solution more realistic higher accuracy on capacity computation

Uniform user distributionUniform user distribution solution more realistic higher accuracy on capacity computation


DOWNLINK Analysis

DOWNLINK Analysis

Cell Range

DL power is shared !


Deriving a mean power per user for one specific service, no more dependent from location, thanks to a uniform user distribution WITH associated probability of Handover status and OCIF

We have the required power at distance d:

Puser i(d) = auser i(d).Ptot+ buser i(d)

to get the mean Power:

Example of mean power: 29.2 dBm 12 supported users at 64 Kbps

DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Power Calculation / Total Power

i user , mean i user , mean i user tot i userR

i user , meanb Ptot . a dr )r( b P )r( a P 20


DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Power Calculation

The total required Node-B power equation can be expressed, in Multi-service:

m.aj.N

bj.NPPP

P

jservicesalloverj

jservicesalloverjCCHotherSCHCPICH

tot

1

Shadowing effect

Parameter Default value Range

P-CPICH power33 dBm (-10dB compared to

the Node B max power)-10 dBm to 43 dBm

P-SCH power - 5dB -15 dB to 35 dBS-SCH power - 5dB -15 dB to 35 dBBCH power (P-CCPCH) - 2 dB -15 dB to 35 dBFACH power (S-CCPCH) - 2 dB -15 dB to 35 dBPCH power (S-CCPCH) - 2 dB -15 dB to 35 dBPICH power - 5 dB -15 dB to 35 dBAICH power - 9 dB -15 dB to 35 dB

4 W are typically considered for

Common Control Channels


The power equation can be expressed in the following form:

The terms YDL and XDL are derived thanks to the traffic module

Downlink Analysis Power Calculation

DOWNLINK Analysis

DOWNLINK Analysis

)traffic(x

)R,traffic(yP

DL

1


XDL & YDL


Capacity assessment in Mono-service PS 64Kbps for one carrier and 20W output power

Example of mean power: 29.2 dBm 832 mW

Total Output Power: 20000 mW, 4000 mW allocated to Control Channels 16000 mW left (42 dBm)

2dB shadowing margin on top of power 40dBm left (~10W)

Possible Number of simultaneous users: 10095 / 832 = 12 users

12 x 64 Kbps = 768 Kbps Throughput

DOWNLINK Analysis

DOWNLINK Analysis

Downlink Analysis Example of capacity assessment in Mono-service


Downlink Analysis Main Process

DOWNLINK Analysis

DOWNLINK Analysis

Assume a cell range Ro

Assume a cell range Ro

Apply Traffic Model to captured traffic and compute total DL

Power for traffic channels

Apply Traffic Model to captured traffic and compute total DL

Power for traffic channels

Compute total DL power Ptot by adding power for common

channels

Compute total DL power Ptot by adding power for common

channels

Ptot = Pmax

?Ptot = Pmax

?

DL RadiusDL Radius

Yes

No, adjust Ro


knowing nb of sub/sqkm per service and the QoS required per service


Key dimensioning radio parametersCritical parameters

Critical parameters that strongly affect the design results: penetration margin (from 0 to 22dB)

Offered service (from 128kbps to 384kbps, double the number of sites)

Propagation model parameters (morpho correction factor Kc)

Probability of coverage (90, 95%)

Mobile transmit power (21 or 24 dBm)

Max allowable UL cell load (e.g. 65%)

EB/No (e.g. 6.4 dB in Uplink)

Multipath channel model (Vehicular or Pedestrian) and speed (3-120km/h)


Downlink analysis is not a conventional link budget but a power analysis

This Power analysis is performed for all users of all services in the cell.

User’s Position has a great impact on capacity The shared resources in Downlink are the Power and the Interference

The peak Power is calculated with a Multi-service traffic model

Downlink AnalysisConclusion

DOWNLINK Analysis

DOWNLINK Analysis


Downlink AnalysisRequired Parameters

Traffic Parameters Services, service class, bit rates, traffic volumes,

GoS Allowed blocking and delay

QoS and Radio Quality BLER and associated Eb/No, Noise Figure

Coverage Requirements Land Usage (Clutter Information), Penetration lossper clutter, Coverage Probability

Subscriber density Subs density per clutter, traffic maps

W-CDMA parameters Available frequencies, chip rate, Other CellInterference Factor, Multipath environement(Vehicular A3km/h, Pedestrian…), OrthogonalityFactor

Radio Parameters Margins (Shadowing, Fast Fading, Body-loss),Gains (antenna, SHO), Propagation Model

Site configuration Antenna height, cable losses

DOWNLINK Analysis

DOWNLINK Analysis


Iterative Multi-service Link Budget

WCDMA Radio ParametersWCDMA Radio Parameters

MULTISERVICE Traffic MULTISERVICE Traffic


DOWNLINK Analysis

DOWNLINK AnalysisTraffic

ModelTraffic Model

Iterative

Process

Iterative

Process

UL cell range DL cell range

Interference Interference &Power





BalancedCell Range

www.alcatel.com

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