06. Power Budget

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Power budget

MODULE 6

ConfigurationPlanningConfigurationPlanning

ParameterPlanning

Area/cellspecific

Handoverstrategies

Other RRM

Site selection and planning

PRE-PLANNING

DETAILED PLANNING

Propagation measurementsCoverage prediction

Load estimationTraff ic distributionPlanned Service and QoSdefinition

Site acquisition

Post- launchoptimisation

Measurementsurveys

Statisticalperformanceanalysis

Quality Efficiency Availability

POST-PLANNING

Coverage and CapacityPlanning

Node-BConfiguration

Antenna lineconfiguration

Power budget

PER SERVICE

Dimensioning

Requirements

and strategyfor coverage,capacity andquality

PER SERVICE

Networkconfiguration

Pre- launchoptimisation

Measurements


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Module 6 Power budget

Objectives

After this module the participant shall be able to:-

Calculate power budget for selected base station

configuration


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Module Contents

Power budget calculation

Power budget balance


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Module Contents




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Power budget

The target of the power budget calculation is to estimate the maximum allowed

path loss on radio path from transmit antenna to receive antenna The minimum Eb/N0(and BER/BLER) requirement is achieved with the maximum

allowed path loss and transmit power both in UL & DL

The maximum path loss can be used to calculate

cell range R

Lpmax_DLLpmax_UL

R


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Power budget Calculations

The calculation is done for each service (bit

rate) separately

The power budget can be used the estimate

link balance (UL vs. DL)

Limiting direction in defined conditions

Link budget

Chip rate 3840.00 DL data rate 12.20

UL Data rate 12.20 DL load 80%

UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS

Thermal Noise Density dBm/Hz -174.0 -174.0

Receiver Noise Figure dB 3.0 8.0

Receiver Noise Density dBm/Hz -171.0 -166.0

Noise Power at receiver [NoW] dBm -105.1 -100.1

Reguired Eb/No dB 4.4 7.9

Soft handover MDC gain dB 0.0 1.0

Processing gain dB 25.0 25.0

Interference margin dB 3.0 7.0

Required Ec/Io at receiver dB -17.6 -11.1

Receiver Sensitivity dBm -122.7 -111.2

Cable loss dB 3.0 0.0

Benefit of using MHA dB 3.0 n/a

Body loss dB n/a 3.0

Antenna gain RX dBi 18.0 0.0

Soft handover gain dB 2.0 2.0

Fast fading margin dB 0.0 0.0

Isotropic power dBm -142.7 -110.2

TRANSMITTING END MS BS

Power per connection dBm 21.0 34.4


Body loss dB 3.0 n/a

Antenna gain TX dBi 0.0 18.0

Peak EIRP dBm 18.0 49.4

Isotropic path loss dB 160.7 159.6 DL Limited!

Voice 12.2 kbit/s, 3 km/h, MacroVoice 12.2 kbit/s, 3 km/h, MacroVoice 12.2 kbit/s, 3 km/h, MacroVoice 12.2 kbit/s, 3 km/h, Macro


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS








Interference margin dB 3.0 7.0Required Ec/Io at receiver dB -17.6 -11.1

















WCDMA Power budgetData Rate in UL and DL depends on secan be asymmetric

Maximum Load needs to be definedfor Dimensioning:

should not exceed 70% should be at least 30% to avoid excessive

cell breathing typically higher in DL than in UL

Maximum Load needs to be definedfor Dimensioning:

should not exceed 70% should be at least 30% to avoid excessive

cell breathing typically higher in DL than in UL


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS

























WCDMA Power budget

Thermal noise density: Theoretical background noise density Depends on temperature

Thermal Noise density[dBm/Hz] is definedas:

Where:k is Boltzman's constant

T is the temperature in Kelvin

in normal +20 C0 conditions the thermalnoise density is -173.98 dBm/Hz

)(*10__ kTLogDensityNoiseThermal

Receiver Noise Figure: Receiver performance

measure; how much receiverdecreases the signal C/I Requirement fromspecificationsfor BTS and MS performance


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS

























WCDMA Power budget Receiver Noise Density[dBm/Hz] Receiver noise density is the sum of thethermal noise density and the receiver noisefigure. Thermal Noise density [dBm/Hz] + Receiver

noise figure [dB] = Receiver Noise Density[dBm/Hz]In order to calculate the thermalNoise power

of the receiver(the receiver noise floor withoutexternal interference) the receiver noise power

is calculated at the WCDMA carrier bandwidth.

receiver noise power [dBm] ==Receiver Noise Density [dBm/Hz] +

10log10(3.84*106)= =-170.98 + 65.84 = -105.14

dBm

RequiredEb/N0

Soft handover MDC gain

Interference margin


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Required Eb/N0

When Eb/N0 is selected, it has to be known in which conditions it is defined(select closest Eb/N0value to the prevailing conditions if available)

Service and bearer

Bit rate, BER requirement, channel coding

Radio channel

Doppler spread (Mobile speed, frequency)

Multipath, delay spread

Receiver/connection configuration

Handover situation Fast power control status

Diversity configuration (antenna diversity, 2-port, 4-port)

Some corrections have to be done in the power budget in case the conditions donot correspond the used Eb/N0

Soft handover MDC gain

Power control gain

Fast fading margin


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Soft Handover MDC Gain UL

Macro Diversity Combining (MDC) gain gives the Eb/N0 improvement in soft

handover situation compared to single link connection

In UL the MDC gain is 0 dB

Significant amount of diversity already exist

2-port UL antenna diversity, multipath diversity (Rake)

The graph includes both Softer and Soft Handover (however it is not possible to see

those gains separately)

Soft Handover combining is done at RNC level by using just selection combining (based on

frame selection)

Softer Handover combining is done at the BTS by using maximal ratio combining

In case of more than 2 connections - no more gain (compared to case of two

branches)


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Soft Handover MDC Gain UL

Tx power, uplink

-0.5

0

0.5

1

1.5

2

0 5 10

Difference between the SHO links (dB)

SHO

MDC

gain(dB)

MS speed 3km/h

MS speed 20km/hMS speed 50km/h

MS speed 120km/h

Soft HOCombining(including softer combininggain for the other branch)Softer HO

Combining

Dynamic SimulatorResult for 2 branches


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Soft Handover MDC Gain DL

In DL there is some combining gain (about 1dB) due to UE maximal ratio

combining

soft and softer handovers included

from MS point there is no difference between soft and softer handover

average is calculated over all the connections taking into account the average

difference of the received signal branches (and UE speed)

40% of the connections in soft handover or in softer handover and 60% no soft handover

taking into account the effect multiple transmitters

combination of dynamic simulator results and static planning tool

in case more than 2 connections - no more gain (compared to case of two branches)

In edge of the cell a 3 4 dB MDC gain can be seen on required DL Eb/N0 in

SHO situations compared to single link reception

Combination of 2 3 signals


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Soft Handover MDC Gain DL

MS speed 3km/hMS speed 20km/h

MS speed 50km/h

MS speed 120km/h

Dynamic SimulatorResult for 2 branches

Total DL Tx power of all branches

-4

-3

-2

-1

0

1

2

0 5 10

Difference between the SHO links (dB)

SHOM

DC

gain(dB)

Soft HO

Softer HO


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Interference Margin

Interference margin is calculated from the UL/DL loading () values

From set maximum planned load

"sensitivity" is decreased due to the network load (subscribers in the network) & in ULindicates the loss in Power budget due to load.

dBLog 110 10IMargin =

20

10

6

1.25

3

25% 50% 75% 99%

IMargin [dB]

Load factor


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS


















Power per connection dBm 21.0 34.4Cable loss dB 0.0 3.0






WCDMA Power budget

Required Signal power is the requiredlowest signal strength that is needed for thatparticular service and load.

Required signal power = Receiver Noise power +required Ec/I0 - Interference Margin + MDC gain

Cable Loss

Benefit of using MHA


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Cable loss

Cable loss is the sum of all signal losses caused

by the antenna line outside the base station

cabinet

Jumper losses

Feeder cable loss

MHA insertion loss in DL when MHA is used

Typical 0.5 dB


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Benefit of using MHA

MHA can be used to improve the base station system noise figure in UL

The benefit achieved by using MHA equals to the noise figure improvement

The benefit of using MHA depends on the cable loss, for example

When Lcable < 5 dB: Benefit of using MHA > Cable loss

When Lcable > 5 dB: Benefit of using MHA < Cable loss

Calculated with Nokia MHA (G = 12 dB, NF = 2 dB) and base station NF = 3 dB

Common assumption is to equal the benefit to the cable loss

vs.Note MHA

insertion loss

for DL


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS
























WCDMA Power budget

Body loss: this parameter describes theadditional loss in power budget. The loss isusually used for speech services where theUEs antenna is often shadowed by the user'shead. Fordata services the body loss can beset to 0dB, because in this case the UE isnormally not close to the body.

Soft handover gain

Fast fading margin

S ft H d G i


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Soft Handover Gain(Gain Against Slow Fading)

Soft handover gain is the gain against shadow fading. This is roughly the gain of

a handover algorithm, in which the best BTS can always be chosen (based on

minimal transmission power of MS) against a hard handover algorithm based on

geometrical distance.

In reality the SHO gain is a function of required coverage probability and the standard

deviation of the signal for the environment.

The gain is also dependent on whether the user is outdoors, where the likelihood of

multiple servers is high, or indoors where the radio channel tends to be dominated bya much smaller number of serving cells.

For indoors users the recommendation is to use smaller SHO gain value

Soft handover gain can be understood also as reduction of Slow Fading Margin (See

Cell range estimation)

S ft H d G i


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Soft Handover Gain(Gain Against Slow Fading)

RNC

Typical average value of the Soft Handover Gain is between 2 and3 dB


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Fast fading margin

Fast fading margin is used as a correction factor forEb/N0at the cell edge, when

the used Eb/N0 is defined with fast power control

At the cell edge the UE does not have enough power to follow the fast fading dips

In DL fast fading margin is not usually applied due to lower power control

dynamic range

Fast fading margin = (average received Eb/N0) without fast PC - (average received Eb/N0) withfast PC

Source: Radio Network Planning & Optimisation for UMTS; J. Laiho, A. Wacker, T.Novosad; Tab. 4.11

Channel:Pedestrian A;antenna diversityassumed

Speed

2.7 km/h

11 km/h

22 km/h

54 km/h

130 km/h


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Fast fading margin

0 0.5 1 1.5 2 2.5 3 3.5 410

15

20

25

dB

0 0.5 1 1.5 2 2.5 3 3.5 4-10

0

10

20

dBm

0 0.5 1 1.5 2 2.5 3 3.5 4-0.5

0

0.5

1

1.5

0 0.5 1 1.5 2 2.5 3 3.5 45

10

15

dB

Seconds

Mobile transmissionpower starts hitting

its maximum value

Eb/N0 targetincreases fast

Received qualitydegrades, more

frame errors

MS moving towards the cell edge


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS
























WCDMA Power budget

Isotropic p oweris the minimum powerneeded for certain service in order to fulfil theEb/No requirement for that service

Isot rop ic p ower= Receiver sensitivity + cable loss -MHA benefit + body loss - antenna gain - softhandover gain ++ fast fading margin

Power per connection


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Power per connection (DL)

The maximum downlink transmit power for each connection is defined by the RNCadmission control functionality

Vendor specific

In Nokia RAN the maximum DL power depends on

Connection bit rate

Service Eb/N0requirement (internal RNC info)

CPICH transmit power and group of other RNC parameters

Actual available DL power depends on maximum total BTS TX power, DL traffic amount

and distribution over the cell (All users share same amplifier)

Example values with 2 W (33 dBm) CPICH power and default Nokia RNC parameters

Service Type Speech CS Data PS Data

Downlink bit rate 12.2 64 64 128 384 kbps

Maximum transmit

power per connection

34.2 37.2 37.2 40.0 40.0 dBm


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS








Interference margindB

3.0 7.0Required Ec/Io at receiver dB -17.6 -11.1
















WCDMA Power budget

Peak EIRPis the maximum transmitted powerafter the antenna.

Peak EIRP = power per connection - cable losses -body loss + antenna gain

EIRP = Equivalent Isotropic Radiated Power

Isotropic path loss: Maximum path lossbetween the transmitting and receiving antennais calculated for UL and DL separately.

Isotropic path loss UL = Peak EIRP - isotropicpower


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Module Contents



WCDMA P b d t UL/DL b l


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Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS








Interference margindB

3.0 7.0Required Ec/Io at receiver dB -17.6 -11.1










Power per connectiondBm

21.0 34.4Cable loss dB 0.0 3.0






WCDMA Power budget UL/DL balance

Power budget can be used to see the

power budget balance, whether UL or DL

is limiting the cell range

Power balance depends on cell load

conditions

With high traffic level DL load is usually

higher due to higherEb/N0requirement

DL limited power budget

With low traffic level UL is usually limiting

du to higher DL power per connection

UL limited power budget

P b d t b l Hi h l l d


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Power budget balance High vs. low load

Link budget



UL Load 5%

4

Uplink Downlink

RECEIVING END BS MS









Required Ec/Io at receiver dB -20.4 -17.6Receiver Sensitivity dBm -125.5 -117.8










Cable loss dB 0.0 3.0Body loss dB 3.0 n/a



Isotropic path loss dB 163.5 166.2 UL limited!


Link budget



UL Load 50%

4

Uplink Downlink

RECEIVING END BS MS









Required Ec/Io at receiver dB -17.6 -11.1Receiver Sensitivity dBm -122.7 -111.2










Cable loss dB 0.0 3.0Body loss dB 3.0 n/a





P b d t f diff t i


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Power budget for different services

Power budget has to be calculated for each service separately

Examples with NRT data services with 2 dBi UE antenna gain and no body loss

50 % UL load and 80 % DL load

Service UL PathLoss DL PathLoss Limitation

Voice 12.2 kbit/s, 3 km/h, Macro 158.9 158.9 UL limited

Voice 12.2 kbit/s, 120 km/h, Macro 159.7 159.4 DL limited

NRT 64 kbit/s, 3 km/h, Macro 157.1 160.6 UL limited

NRT 64 kbit/s, 120 km/h, Macro 158.0 161.1 UL limited

NRT 64/128 kbit/s 3 km/h, Macro 157.1 158.7 UL limited

NRT 64/128 kbit/s 120 km/h, Macro 158.0 159.2 UL limited

NRT 64/384 kbit/s, 3 km/h, Macro 157.1 153.8 DL limited

NRT 64/384 kbit/s, 120 km/h, Macro 158.0 154.3 DL limited

M d l 6 P b d t


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Module 6 Power budget

Summary

Power budget calculation involves many estimates and

assumptions Educated guess

06. Power Budget

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