Module 6 – Power budgetObjectives

After this module the participant shall be able to:-

•Calculate power budget for selected base

station configuration

Module Contents

• Introduction

• Power budget calculation

• Power budget balance

Introduction• R99 DCH uplink link budget

– DPDCH and DPCCH are included– Uplink Eb/No figures include the overhead generated by the

DPCCH

• HSDPA uplink link budget– DPDCH, DPCCH and HS-DPCCH are included– Composite Eb/No figure is derived by adding the peak HS-

DPCCH overhead to the R99 DCH Eb/No (this overhead often appears in the transmitter section of the link budget)

• HSUPA uplink link budget– E-DPDCH, E-DPCCH, DPCCH, DPDCH and HS-DPCCH to consider– New set of Eb/No figures generated from link level simulations

which include the E-DPDCH, E-DPCCH and DPCCH

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 calculatecell range R

Lpmax_DL

Lpmax_UL

R

Module Contents

• Introduction

• Power budget calculation– R99 power budget– HSDPA power budget– HSUPA power budget


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%

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Uplink DownlinkRECEIVING END BS MSThermal Noise Density dBm/Hz -174.0 -174.0Receiver Noise Figure dB 3.0 8.0Receiver Noise Density dBm/Hz -171.0 -166.0Noise Power at receiver [NoW] dBm -105.1 -100.1Reguired Eb/No dB 4.4 7.9Soft handover MDC gain dB 0.0 1.0Processing gain dB 25.0 25.0Interference margin dB 3.0 7.0Required Ec/Io at receiver dB -17.6 -11.1Receiver Sensitivity dBm -122.7 -111.2Cable loss dB 3.0 0.0Benefit of using MHA dB 3.0 n/aBody loss dB n/a 3.0Antenna gain RX dBi 18.0 0.0Soft handover gain dB 2.0 2.0Fast fading margin dB 0.0 0.0Isotropic power dBm -142.7 -110.2

TRANSMITTING END MS BSPower per connection dBm 21.0 34.4Cable loss dB 0.0 3.0Body loss dB 3.0 n/aAntenna gain TX dBi 0.0 18.0Peak EIRP dBm 18.0 49.4Isotropic 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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WCDMA Power budgetData Rate in UL and DL depends on service, can 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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WCDMA Power budgetThermal noise density: • Theoretical background noise density• Depends on temperature• Thermal Noise density [dBm/Hz] is defined as:

Where: k is Boltzman's constant T is the temperature in Kelvin

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

)(*10__ kTLogDensityNoiseThermal

Receiver Noise Figure: • Receiver performance measure; how much receiver decreases the signal C/I• Requirement from specifications for BTS and MS performance



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WCDMA Power budgetReceiver Noise Density [dBm/Hz] • Receiver noise density is the sum of the thermal noise density and the receiver noise figure.• Thermal Noise density [dBm/Hz] + Receiver noise figure [dB] = Receiver Noise Density [dBm/Hz]In order to calculate the thermal Noise power of the receiver (the receiver noise floor without external 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 dBmRequired Eb/N0

Soft handover MDC gain

Interference margin

Required Eb/N0

• When Eb/N0 is selected, it has to be known in which conditions it is defined (select closest Eb/N0 value 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 do not correspond the used Eb/N0– Soft handover MDC gain– Power control gain– Fast fading margin

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)

Soft Handover MDC Gain – ULTx power, uplink

-0.5

0

0.5

1

1.5

2

0 5 10

Difference between the SHO links (dB)

SH

O M

DC

gain

(dB

)

MS speed 3km/h

MS speed 20km/h

MS speed 50km/h

MS speed 120km/h

Soft HOCombining(including softer combining gain for the other branch)

Softer HOCombining

Dynamic SimulatorResult for 2 branches

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

Soft Handover MDC Gain – DL

MS speed 3km/h

MS 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)

SH

O M

DC

gain

(dB

)

Soft HO

Softer HO

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 UL

indicates the loss in Power budget due to load.

dBLog 110 10IMargin =

20

10

6

1.253

25% 50% 75% 99%

IMargin [dB]

Load factor



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WCDMA Power budgetRequired Signal power is the required lowest signal strength that is needed for that particular service and load. Required signal power = Receiver Noise power + required Ec/I0 - Interference Margin + MDC gain

Cable Loss

Benefit of using MHA

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

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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WCDMA Power budget

Body loss: this parameter describes the additional loss in power budget. The loss is usually used for speech services where the UEs antenna is often shadowed by the user's head. For data services the body loss can be set to 0dB, because in this case the UE is normally not close to the body.

Soft handover gain

Fast fading margin

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 by a 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)

Soft Handover Gain(Gain Against Slow Fading)

RNC

Typical average value of the Soft Handover Gain is between 2 and 3 dB

Fast fading margin• Fast fading margin is used as a correction factor for Eb/N0 at 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) with fast PC

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

Channel: Pedestrian A;antenna diversity assumed

Speed

2.7 km/h

11 km/h

22 km/h

54 km/h

130 km/h

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 transmission power starts hitting its maximum value

Eb/N0 targetincreases fast

Received qualitydegrades, more

frame errors

MS moving towards the cell edge



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WCDMA Power budget

Isotropic power is the minimum power needed for certain service in order to fulfil the Eb/No requirement for that service

Isotropic power = Receiver sensitivity + cable loss - MHA benefit + body loss - antenna gain - soft handover gain ++ fast fading margin

Power per connection

Power per connection (DL)• The maximum downlink transmit power for each connection is defined by the RNC

admission control functionality– Vendor specific

• In Nokia RAN the maximum DL power depends on– Connection bit rate– Service Eb/N0 requirement (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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WCDMA Power budget

Peak EIRP is the maximum transmitted power after the antenna.

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

EIRP = Equivalent Isotropic Radiated Power

Isotropic path loss: Maximum path loss between the transmitting and receiving antenna is calculated for UL and DL separately.

Isotropic path loss UL = Peak EIRP - isotropic power

Module Contents

• Introduction



HS-PDSCH LINK BUDGET• In HSDPA link budget, one of two approaches can be adopted

– Target uplink bit rate can be specified and link budget completed from top to bottom to determine the maximum allowed path loss

• HS-PDSCH SINR should correspond to the targeted cell edge throughput– Existing maximum allowed path loss can be specified and link budget

completed from bottom to top to determine the achievable uplink bit rate at cell edge

• The total transmit power assigned to the HS-PDSCH and HS-SCCH depends on RNC parameters and CCCH power and in shared carrier also on DCH traffic load

• HS-PDSCH does not enter soft handover

• An overhead for HS-DPCCH channel has to be taken into account in UL when HSDPA is active

HS-PDSCH power budgetMax Tx power is the allocated power for HS-PDSCH which depends on the CCCH and in shared carrier also on the required DCH power

SINR Requirement depends on the required cell edge throughput

Spreading gain is calculated from the used spreading factor 16

Soft handover gain is 0 dB because no SHO on HS-PDSCH

Cell edge throughput affects the required SINR

Module Contents

• Introduction



• Similar to an HSDPA link budget, one of two approaches can be adopted

• target uplink bit rate can be specified and link budget completed from top to bottom to determine the maximum allowed path loss

• existing maximum allowed path loss can be specified and link budget completed from bottom to top to determine the achievable uplink bit rate at cell edge

• Majority of uplink link budget is similar to that of a R99 DCH

• HSUPA uplink link budget makes use of Eb/No figures rather than SINR figures

UplinkDownlinkR99 DCH Eb/No EbNoHSDPA Eb/No SINRHSUPA Eb/No SINR

HSUPA Uplink Link Budget (I)

Cell Edge ThroughputTarget BLERPropagation Channel

used to index the Eb/No look-up table and determine an appropriate Eb/No figure

Eb/No look-up tables

• Eb/No values are included for• Bit rates 32 kbps to 1920 kbps

• Target BLER 1, 5 and 10 %

• Propagation channels Vehicular A 30 km/hr and Pedestrian A 3 km/hr

• Target BLER figures are applicable to each MAC-e transmission, e.g. a 10 % Target BLER corresponds to a BLER of 0.01 % after 4 transmissions

• Eb/No values include E-DPDCH, E-DPCCH and DPCCH

HSUPA Uplink Link Budget (II)

• The own connection interference factor reduces the uplink interference floor by the UE’s own contribution to the uplink interference, i.e. by the desired uplink signal power

• This factor is usually ignored in R99 DCH link budgets because the contribution from each UE is relatively small

• This factor is included in the HSUPA link budget because uplink bit rates can be greater and the uplink interference contribution from each UE can be more significant

HSUPA Uplink Link Budget (III)Transmit section of link budget is identical to that of a R99 DCH link budgetTransmit antenna gain and body loss can be configured for either a data card or mobile terminal

Interference floor = Thermal noise + Noise Figure + Interference Margin - Own Connection InterferenceInterference Margin = -10*LOG(1- Uplink Load/100)Own Connection Interference = 10*LOG(1+ EbNo * R / W)

Module Contents

• Power budget calculation




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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 higher Eb/N0 requirement DL limited power budget

• With low traffic level UL is usually limiting du to higher DL power per connection UL limited power budget

Power budget balance – High vs. low loadLink budget

Chip rate 3840.00 DL data rate 12.20UL Data rate 12.20 DL load 10%

UL Load 5%4


TRANSMITTING END MS BSPower per connection dBm 21.0 34.4Cable loss dB 0.0 3.0Body loss dB 3.0 n/aAntenna gain TX dBi 0.0 18.0Peak EIRP dBm 18.0 49.4Isotropic path loss dB 163.5 166.2 UL limited!




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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 loadService UL PathLoss DL PathLoss LimitationVoice 12.2 kbit/s, 3 km/h, Macro 158.9 158.9 UL limitedVoice 12.2 kbit/s, 120 km/h, Macro 159.7 159.4 DL limitedNRT 64 kbit/s, 3 km/h, Macro 157.1 160.6 UL limitedNRT 64 kbit/s, 120 km/h, Macro 158.0 161.1 UL limitedNRT 64/128 kbit/s 3 km/h, Macro 157.1 158.7 UL limitedNRT 64/128 kbit/s 120 km/h, Macro 158.0 159.2 UL limitedNRT 64/384 kbit/s, 3 km/h, Macro 157.1 153.8 DL limitedNRT 64/384 kbit/s, 120 km/h, Macro 158.0 154.3 DL limited

Module 6 – Power budgetSummary

•Power budget calculation involves many

estimates and assumptions Educated guess

Link Budget

Documents

Transcript of Link Budget