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Table of Contents

1 Introduction ............................................................................................................................ 4

2 R99 Link Budget ..................................................................................................................... 4

2.1 Maximum Allowable Path Loss ....................................................................................... 4

2.2 Main R99 Link Budget Parameters ................................................................................. 5

2.3 Case Study ...................................................................................................................... 10

3 HSDPA Link Budget ............................................................................................................. 11

3.1 HSDPA Link Budget Procedure .................................................................................... 11

3.2 Case Study ...................................................................................................................... 12

4 HSUPA Link Budget ............................................................................................................. 13

4.1 HSUPA Link Budget Procedure .................................................................................... 13

4.2 Case study ...................................................................................................................... 14


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WCDMA Link Budget Principle and Case Study

Abstract：This article first presents an overview of WCDMA link budget procedure

and then fundamental parameters used in link budget are explained in detail.

1 Introduction

The purpose of this document is to illustrate the link budget principle and at the same time

provide detailed introduction to certain fundamental link budget parameters and some case

study.

The document is organized as follows:

Chapter 2 presents the R99 link budget principle and case study.

Chapter 3 shows the HSDPA link budget principle and case study.

Chapter 4 presents the HSUPA link budget principle and case study.

2 R99 Link Budget

2.1 Maximum Allowable Path Loss

Link Budget is the first step for radio network dimensioning. For an actual network, the

effective coverage of NodeB depends on not only the coverage requirement but also the TX

power and Rx sensitivity of NodeB and UE. Since the properties of NodeB and UE are

different from each other considerably, the actual permitted uplink and downlink path loss

vary too. Because the actual effective coverage range will depend on the lower value of them,

it is necessary to calculate the permitted maximum allowable propagation path loss of both

uplink and downlink.

The Maximum Path loss of uplink and downlink can be described by the formulas below:

UESFFMSFMIMLbLpantennaGaBSLfBSPoutDLPL _____

BSSFFMSFMIMLbLpantennaGaBSLfUEPoutULPL _____

Where:

DLPL _: Downlink maximum path loss

ULPL _: Uplink maximum path loss

BSPout _: Maximum TX power of BS traffic channel

UEPout _: Maximum TX power of UE

BSLf _: Cable loss


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antennaGa_ : BS antenna gain

Lp : Building penetration loss (required in indoor coverage)

Lb : Human body loss

IM : Interference margin (related to system design capacity)

SFM : Slow fading margin or Log-Normal Fading (including soft handover gain against SFM)

FFM : Fast fading margin (including soft handover gain against FFM)

BSS _ : Sensitivity of BS receiver (related to factors like the service and multi-path condition)

UES _ : Sensitivity of UE receiver (related to factors like the service and multi-path condition)

2.2 Main R99 Link Budget Parameters

In the following sections, a detailed description of the main parameters used in link budget is

provided.

1. Receiver sensitivity (S_BS, S_UE)

Receiver sensitivity is mainly dependent upon noise figure and Eb/No and service bearer

rate R (kbps). The calculation formulas of S_BS and S_UE are:

S_BS = Thermal Noise Power + Noise Figure of NodeB + Eb/No + Processing Gain

S_UE = Thermal Noise Power + Noise Figure of UE + Eb/No + Processing Gain

* R is the service bearer rate.

Thermal Noise Power (Nth)

Thermal noise Power is the noise density generated by environment and equals to

WTKNth

With K being Boltzmann’s constant 1.38*10-23

and T the temperature in Kelvin. When T is

293 in Kelvin (20 in Celsius), TK is (-174dBm/Hz), W is 10×log (3840000), and thN is

(-108dBm/3.84MHz.)

Noise Figure (Nf)

Noise figure is the additional amount of noise generated by a receiver. For UE of 2100MHz,

typical noise figure is 7dB. For Huawei’s NodeB, latest noise figure is 1.6dB. It should be

noticed that noise figure of NodeB is equipment related and may be different for various

vendors.

Eb/No

Eb/No is the required bit energy over the density of total noise to maintain service quality.

The Eb/No values are related with the service type, the target BLER, the channel models and

the user speed. The table below shows the required Eb/No under different conditions.

Table1 Eb/NO requirement


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Service BLER Channel Model

Uplink Eb/NO

Downlink Eb/NO

AMR12.2k 1.00% TU3 5.4dB 7.8 dB

RA120 4.5 dB 8.3 dB

CS64k 0.10% TU3 2.8 dB 6.3 dB

RA120 2.8 dB 6.8 dB

CS64k 1.00% TU3 2.5 dB 5.4 dB

RA120 2.3 dB 6 dB

In dense urban and urban scenarios TU (Typical Urban) channel model is often used with

user speed being 3km/h or 50km/h, while in the rural environment the RA channel model is

often used with 120km/h speed.

Since two receiving antenna is typical configuration of NodeB, the uplink Eb/No that HUAWEI

provided above already includes two antenna receiving diversity gain.

Processing Gain (PG)

Processing gain is related with the service bearer rate, and the detail formula is present

below:

Processing Gain = 10 × log (3840 / R (Kbps)), R is the service bearer rate.

Service Processing Gain

AMR 12.2K 25.0

CS64K / PS64K 17.8

PS128K 14.8

PS 384K 10.0

2. Body Loss

Body loss is the loss at UE due to the presence of human body. Typical value is 3dB for

voice and low data rate services. For services with data rates no less than 64kbps, no body

loss is taken into account considering that terminals are usually held kept a distance from the

subscribers’ body.

3. Penetration Loss

When indoor coverage is required to coverage by outdoor macro NodeBs, buliding

penetration loss needs to be considered. Building penetration loss is related to such factors

as incidence angle of the radio wave, the building construction (the construction materials

and number and size of windows), the internal building layout and Frequency. Building

penetration loss is highly dependent on specific environment and morphology and varies

greatly. For instance, the wall thickness in Siberian tends to be larger than that of Singapore

in order to resist coldness and hence the former’s building penetration loss is

correspondingly larger.

In addition, sometimes vehicular coverage may be required and consequently vehiculare

penetration loss also needs to be included in link budget process. In fact, only one

penetration loss, the maximum of building penetration loss and vehicular penetration loss, is


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included in link budget. Since typical vehicular penetration loss is around 8dB which is

smaller than building penetration loss, building penetration loss rather than vehicular

penetration loss is usually included in link budget process.

4. Interference Margin (IM)

Interference margin is the required margin in the link budget due to the noise rise caused by

system load (the noise rise due to other subscribers).The higher the system load, the larger

the interference margin.

For uplink, the relationship between uplink load and interference margin is

)1(log*10 10 ULuplinkIM

And depicted in the picture below

For downlink, the calculation of downlink interference margin is more complicated than uplink.

Many factors besides downlink load also have impact on downlink interference margin, such

as maximum transmission power of NodeB, cell coupling loss, orthogonal property of channel

model and adjacent-to-own cell interference ratio at cell edge.

5. Fast fading margin

In WCDMA, user signals should be received at the BS with equal power all the time and for

downlink the transmitted TCH power should be as small as possible while maintaining the

required Qos. This implies that fast fading dips are compensated by the power control

algorithm, which requires additional headroom at both UE and NodeB in order to let UE and

NodeB following the power control commands at cell edge. Simulation results prove that the

required fast fading margin equals to the gain of fast power control. Obviously, no fast fading

margin is needed if fast power control brings no gain at all.

Since it’s a margin against fast fading, it decreases with user speed and the number of

multi-path.

SHO gain over fast fading

In SHO more than one branch exists and the multiple received signals are combined. As a


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result, the fast power control no longer has to compensate for the deepest fade and both the

required transmission power and received signal level can be reduced.

SHO gain over fast fading refers to the gains of combining the multiple received signals

(MDC gain) and less peaky fast power control due to SHO. In other words, SHO gain against

slow fading is not included.

6. SFM (Slow Fading Margin)

The log normal fading margin (also known as slow or shadow fading margin) corresponds to

the variation in mean signal level caused by shadowing effect of physical environments such

as buildings and hills.

The fading margin is the amount of margin necessary to achieve the required area reliability

for a given standard deviation. Obviously, the higher area coverage reliability requires the

larger SFM. In addition, the value of standard deviation will also influence the required fading

margin and the larger the standard deviation, the larger the required SFM.

SFM without SHO

The following equation is Jake’s singe cell reliability equation that determines the area

reliability of a single cell which is commonly used to approximate the reliability of a site.

)

1(1)

21exp()(1

2

12 b

aberf

b

abaerfFu

Where:

2

0

rPxa

, 2

log10 10

enb

,

uF is cell coverage probability, rP is the received signal mean at cell edge, n is the

propagation constant, 0x is the average signal strength threshold, is the slow fading

standard deviation and erf is the error function.

Coverage Probability:

P COVERAGE (x) = P [F(x) > Fthreshold ] Probability Density

SFM required Without SFM

With SFM

Fthreshold

Received Signal Level [dBm]


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STD (Slow Fading Standard Deviation)

The standard deviation is a measured value that is obtained from various clutter types. It

basically represents the variance (log-normally distributed around the mean value) of the

measured RF signal strengths at a certain distance from the site.

Therefore, the standard deviation would vary by clutter type. Depending on the propagation

environment, the log-normal standard deviation can easily vary between 6 and 8 dB or even

greater. Assuming flat terrain, rural or open clutter types would typically have lower standard

deviation levels than the suburban or urban clutter types. This is due to the highly obstructive

properties encountered in an urban environment that in turn will produce higher standard

deviation to mean signal strengths than that experienced in a rural area.

A composite standard deviation can be obtained by the following formula:

22

2

2

1 nc

where n is the log normal standard deviation for environment n. This composite standard

deviation may sometimes be used if there are two or more environments (for instance,

outdoors and in-building) which have their own standard deviation. For example, if the

standard deviation is 8 dB for outdoors and 10 dB for in-building, the composite standard

deviation to use in Jake’s equation would be ~ 12 dB.

SHO gain over slow fading

SHO gain over slow fading is also known as the Multi-Cell gain because in soft handover

more than 1 branch exists and hence the coverage probability increases which would result

in the decreasing of required slow fading margin.

Suppose that soft handover has 2 branches, and the orthogonality of the two radio link

branches on slow fading is 50%. We can calculate the slow fading margin required with soft

handovers based on the former assumptions, and compare it with the slow fading margin

required without soft handover to get the SHO gain over slow fading.

It should be noted that in a real network more than 2 branches may be involved in a soft

handover, though this probability is rather slow, the corresponding SHO gain is slightly higher

than that of a 2 branch soft handover. Therefore, the SHO gain derived from the above

supposition on 2-brance handovers is relatively conservative.

SHO gain over slow fading is dependent on the required area coverage probability, the

propagation path loss slope and the STD. The following table gives the calculated SHO gain

over slow fading and the propagation path loss slope equals to 3.59.

Table2 SHO gain over slow fading

Standard Deviation(Indoor)

Coverage Probability

Slow Fading Margin(Non SHO)

SHO Gain over Slow Fading

Slow Fading Margin(With SHO)

11 (Dense Urban) 0.95 13.1dB 5.6dB 7.5dB

9 (Urban) 0.95 10.2dB 4.6dB 5.6dB


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8 (Suburban) 0.95 8.7dB 4dB 4.7dB

2.3 Case Study

Assumption:

Cable Loss: 0.5 dB (Distribution system)

Cell Load: 50% for uplink and 90% for downlink (considering HSPA services)

Antenna Gain: 18 dBi

Penetration Loss: 20 dB (Dense urban)

Maximum UE transmitting power: 21 dB

Propagation Model: SPM (Standard propagation model)

BS average antenna height: 30 meters

Procedures of uplink and downlink link budget are provided in the following table:

Table3 Uplink and Downlink Link Budget Procedures

Link Budget AMR12.2k CS64k Calculation Formula

Uplink Downlink Uplink Downlink

Transmitting Power(dBm) 21 30 21 36 a

BS Antenna Gain (dBi) 18 18 18 18 b

Cable Loss(dB) 0.5 0.5 0.5 0.5 c

Body Loss(dB) 3 3 0 0 d

Load Factor 0.5 0.9 0.5 0.9

Interference Margin(dB) 3.01 5.44 3.01 5.44 e

Fast Fading Margin(dB) 0.8 0 1.8 0 f

Area coverage probability 95% 95%

Slow fading standard deviation (dB) 11 11

Slow Fading Margin(dB) 7.54 7.54 7.54 7.54 g

Penetration Loss(dB) 20 20 20 20 h

Thermal Noise (dBm/3.84MHz) -108.13 -108.13 -108.13 -108.13 j

Receiver Noise Figure(dB) 1.6 7 1.6 7 k

Required Eb/NO(dB) 5.4 7.8 2.8 6.3 l

Processing Gain(dB) 24.98 24.98 17.78 17.78 m=W/R

Receiver Sensitivity(dB) -126.11 -118.31 -121.51 -112.61 i=j+k+l-m

Maximum Path Loss 130.26 129.83 127.66 133.13 PL=a+b-c-d-e-f-g-h-i

According to the maximum path loss, BS antenna high and propagation model, the cell

radius can be obtained.

Coverage Service AMR12.2k CS64k

Uplink Downlink Uplink Downlink

Cell Radius (Km) 0.47 0.45 0.39 0.57


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3 HSDPA Link Budget

3.1 HSDPA Link Budget Procedure

The HSDPA link budget is usually base on the R99 link budge to get the cell edge throughput

in downlink. The link budget for HSDPA is more complex than R99, and the cell edge

throughput need to be calculated depend on simulation result, which is closed related with

cell edge Ec/No.

For HSDPA, soft handover gain and fast fading margin should not be considered in link

budget, since neither fast power control nor soft handover is adopted in HS-PDSCH channel.

The figure below shows the procedure of HSDPA link budget:

The main step of HSDPA link budget is present below:

1. According to the cell radius comes from R99 dimensioning, the downlink coupling loss

can be calculated.

2. Cell edge Ec/No will be carry out base on the formula below:

)

10

log(*10

10

_

max

NtNFCoupleLossDL

DL

DSCHHS

Pf

P

No

Ec＋＋

Where:

DSCHHSP : Total power of HS-DSCH channel

: Non-orthogonality Factor

f: Neighbor cell interference factor

CoupleLossDL_ ：Downlink coupling loss

Cell Radius

Cell Edge Ec/No

HSDPA Power Allocation

Simulation

Ec/No => Throughput

UE Category,

Receiver Type…

Cell Edge Throughput

Downlink Coupling Loss


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DL: Downlink target load, including R99 and HSDPA service

maxP: Max transmitter power of downlink

Nt : Thermal noise power spectral density, typical value is -108.16dBm

fN: Receiver noise Figure, typical value is 7dB

3. Cell edge throughput can be calculated base on the simulation result, while more

factors have been considered, such as UE Category and HSDPA codes allocation.

3.2 Case Study

Assumption:

Channel type: TU3

Non-orthogonality factor: 0.5

Neighbor cell interference factor: 1.78

HSDPA code resource: 5

Cell radius: 0.36 Km

UE Category: 8

Max transmitter power of downlink: 20000 mw

Total power of HSDPA: 6000 mw (30% downlink power allocation)

According to the assumption above, the DL_CoupleLoss for HSDPA is calculated below:

144.662013.1018-0.51.37)(127.69

____

LpSFMLbantennaGaBSLfDLPLCoupleLossDL NSHO

Where:

DLPL _: Downlink maximum path loss

BSLf _: Cable loss

antennaGa_ : BS antenna gain

Lp : Building penetration loss (required in indoor coverage)


NSHOSFM : Slow fading margin or Log-Normal Fading (without soft handover gain against SFM)


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dB

Pf

P

No

EcNtNFCoupleLossDL

DL

DSCHHS

2.10)

1020000*9.0*)78.15.0(

6000log(*10

)

10

log(*10

10

716.10866.144

10

_

max

＋＋

Base on the simulation result, the cell edge throughput for HSDPA can be obtained as

173.80 Kbit/S.

4 HSUPA Link Budget

4.1 HSUPA Link Budget Procedure

The procedure of HSUPA link budget is almost the same with HSDPA. The cell edge

throughput is also depended on the simulation result. The main difference between HSUPA

and HSDPA is that power control, soft handover gain and UE power back off are needed to

be considered in the cell edge Ec/No evaluation.

For HSUPA, the UE power PAR (Peak to average rate) is increase due to the multi-code

transmission of uplink users, and power back off is needed to protect UE’s PA (Power

amplifier).

The figure below shows the procedure of HSUPA link budget.

The main step of HSUPA link budget is present below:

1. Cell edge Ec/No for HSUPA can be calculated base on the formula below:

antennaGaFFMIMSFMLpULPLPUEPoutsignalR backoff ____

)_(_ BSLfNfNtsignalRNo

Ec

Cell Radius

Cell Edge Ec/No

UE Maximum Power

Simulation

Ec/No => Throughput

Cell Edge Throughput

UE Category,

Receiver Type…


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Where:

signalR _ : Minimal receive signal level required

UEPout _: Maximum TX power of UE

backoffP: UE power back off

ULPL _: Uplink path loss

BSLf _: Cable loss

antennaGa_: BS antenna gain

Lp: Building penetration loss (required in indoor coverage)


IM : Interference margin (related to system design capacity)

SFM : Slow fading margin or Log-Normal Fading (including soft handover gain against SFM)

FFM : Fast fading margin (including soft handover gain against FFM)

Nt : Thermal noise power spectral density, typical value is -108.16dBm

fN: NodeB Receiver Noise Figure, typical value is 1.6dB for Huawei

2. Cell edge throughput can be calculated base on the simulation result, while more

factors have been considered, such as UE Category, receiver type. Part of simulation

result is presented as below:

4.2 Case study

Assumption:

Channel type: TU3

Cell radius: 0.36 Km

UEPout _ : 24 dBm

backoffP: 1.5 dB

-25

-20

-15

-10

-5

0

5

10

69 507.6 978 1353 1927.8 2706 4050

Bearer Rate

Ec/N

0

TU3_SBLER70%TU3_SBLER30%TU50_SBLER70%TU50_SBLER30%RA3_SBLER70%RA3_SBLER30%


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IM : 3 dB for 50% uplink load

According to the assumption above, the Ec/No for HSUPA can be calculated below:

67.11)5.06.116.108(180354.72069.1275.124

)_(___

BSLfNfNtantennaGaFFMIMSFMLpULPLPUEPoutNo

Ecbackoff

Base on the simulation result, the cell edge throughput for HSUPA can be obtained as 255.6

Kbit/S.

wcdma link budget principle and procedure-v1[1][1].2

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