New_1x_description of Link Budget Paramet

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2004. Feb.

ED 04

System Lab. 2 (Wireless)

Description of

Link Budget Parameter


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Description of Link Budget Parameters 2004-02-27

System Lab. 2Samsung Electronics Proprietary

I

CONTENTS

1. OVERVIEW....................................................................................................................................... 2

2. PARAMETERS ................................................................................................................................. 22.1 Forward link ...................................................................................................................................................22.2 Reverse link .....................................................................................................................................................8

3. EXAMPLES OF LINK BUDGETS................................................................................................... 113.1 1X Forward link Voice .................................................................................................................................113.2 1X Forward link data...................................................................................................................................113.3 1X Reverse link voice ...................................................................................................................................123.4 1X Reverse link data.....................................................................................................................................12


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Link Budget Parameters Explanation 2004-02-05


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1. Overview

The link budget is to estimate the maximum cell range satisfying required Eb/No which is related to the some

quality (FER) target. In the link budget some factors such as the antenna gains, cable losses, diversity gains,

fading margins, and etc., are taken into account. The output of the link budget calculation is the MAPL

(Maximum Allowed Propagation Path Loss) i.e., the maximum tolerable mean path loss in the link.

2. Parameters

2.1 Forward link

Test environment

In the link budget the three test environments, indoor, outdoor and vehicle, are considered for both voice and

data service. For those environments two channel models, Pedestrian B (Ped-B) and Vehicular B (Veh-B),

recommended by ITU-R M. 1225 are used for indoor/outdoor and vehicle environments, respectively.

Traffic channel fraction of total power, Ec/Ior(dB)

Ec/Ior is the ratio of the traffic channel energy per chip on a given channel relative to the total transmitted

power spectral density at the Base station (BS). Note that it is also the fraction of the power allocated to the

channel from the total BS transmitted power used. It is often utilized in down link performance requirements. In

Samsung link budget table the simulation results by CDG (CDMA Development Group) evolution study report

and by Samsung are used for voice and data service, respectively.

(1) Voice service

Figure 1 and 2 show Ec/Ior for voice channel according to the geometry in CDMA2000 1X and they are

adopted from CDG evolution study report. Ped-B and Veh-B environment are shown in Figure 1 and 2,

respectively. In Samsung link budget, the Ec/Ior value at geometry 0 dB represents the cell edge condition with

0 dB soft handoff (SHO) imbalance is chosen.

(2) Data service

CDMA2000 1X Samsung simulation results in Ped-2 path, turbo code environment at geometry 4 dB for Ped-B,

and geometry 0 dB for Veh-B with respect to the 153.6 kbps data rate are shown in Figure 3 and 4, where 5%

target FER is given.


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cdma2000 1X , Ped - B, no - TD, RC3 (R 1/4)

- 20

- 18

- 16

- 14

- 12

- 10

- 8- 6

- 4

- 2

0

- 6 - 3 0 3 6 9 12

Geometry [ dB]

Ec/ordB]

0 dB SHO Imbalance

3 dB SHO Imbalance

6 dB SHO Imbalance

No SHO

F igure 1. CDMA2000 1X, Ped-B, no-TD , RC3, voice channel Ec/I or according to geometry.

cdma2000 1X , Veh - B, no - TD, RC3 (R 1/4)

- 20

- 18

- 16

- 14

- 12

- 10

- 8

- 6

- 4

- 2

0

- 6 - 3 0 3 6 9 12

Geo metry [ dB]

Ec/ordB]

0 dB SHO Imbalance

3 dB SHO Imbalance

6 dB SHO ImbalanceNo SHO

F igure 2. CDMA 2000 1X, Veh-B, no-TD , RC3, voice channel Ec/I or according to geometry.


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cdma2000 1X , Ped - B, no - TD, RC3 (153.6 kbps)

- 12

- 10

- 8

- 6

- 4

- 2

0

2 4 6 8 10 12

Geometry [ dB]

Ec/ordB]

F igure 3. CDMA2000 1X, Ped-B, tur bo code, Samsung simu lation resul t.

cdma2000 1X , Ved - B, no - TD, RC3 (153.6 kbps)

- 14

- 12

- 10

- 8

- 6

- 4

- 2

0

0 2 4 6 8 10 12

Geometry [ dB]

Ec/ordB]

F igure 4. CDMA2000 1X, Veh-B, turbo code, Samsung simu lation resul t.

BS maximum transmitter power per traffic channel (dBm) is calculated from traffic channel fraction

(Ec/Ior) of total power and BS maximum transmitter power, 43 dBm.

Cable, connector and combiner losses (dB) are the combined losses of all transmission system components

between the transmitter output and the antenna input. Note that all losses in positive dB values in link budget

table. A typical value is 3 dB.

BS transmitter antenna gain (dBi) is the maximum gain for the transmitter antenna in the horizontal plane.It is specified as dB relative to an isotropic radiator.


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BS transmitter EIRP per traffic channel (dBm) is the effective transmitting power in traffic channel. It is

calculated by the summation of BS maximum transmitter power per traffic channel (dBm), transmission

system losses (-dB), and the transmitter antenna gain (dBi).

MS receiver gain (including body loss etc.) (dBi) is the total gain affected by the MS receiver antenna gain

(dBi), receiver system loss (-dB) and body loss (-dB). The typical values of receiver system and body lossesare 0 dB and 3 dB, respectively.

Thermal Noise Density (dBm/Hz) is the noise density generated by thermal agitation of electrons in a

conductor. It can be calculated by the following equation, N=KTW/Hz, where, K is Boltzman constant (-

228.6 dBW/KHz) and T is the absolute temperature. Therefore, it is the function of temperature, T and

bandwidth, W.At the room temperatureN = -174 dBm/Hz

Receiver Noise Figure(dB) is represented by the ratio, usually expressed in dB, of the thermal noise power

at the output to that at the input. 8 dB is a typical value for commercial mobile system (MS). .

Total effective noise + interference density [dBm/Hz] is the effective noise. It is estimated by simulation.

In simulation, 2-tier hexagonal cell structure is used to evaluate, and the following geometries are used for

cell edge condition.

Service Type Ped-B Veh-B

Voice Geometry 0 dB Geometry 0 dB

Data Geometry 4 dB Geometry 0 dB

Information Rate (Bit rate) (dB-Hz) is the channel bit rate, and is the dB scale of bit rate.

Required Eb/(No+Io) (dB) is the ratio of the required energy per bit to interference power spectral density

for satisfying the proper target FER, 1% for voice and 5% for data service. These parameters are obtained by

long-term link level simulation using given FER condition.

Receiver Sensitivity (dBm) is the required minimum received signal power at receiver without margin and

gain.

Handoff Gain (dB) is the effective gain due to the duration of the transmitter signal at receiver. The gain is

dependent on the standard deviation of the individual fading processes of the two paths and the relative

correlation between the two paths. Therefore, the handoff gain increases as the standard deviations of the

fading processes increase. Handoff gain is estimated by analytical method1.

Penetration Loss (dB) is the required margin to overcome another losses due to the car and the building.

a. Indoor penetration loss

It is associated with the degradation of the RF signal caused by a building structure. Variations result

from construction material, building layout, user location inside the building and direction from base

1 For a detailed discussion of handoff gain, please see: A. J. Viterbi, A. M Viterbi, K. S. Gilhousen, E. Zehavi, Soft Handoff Extends

CDMA Cell Coverage and Increased Reverse Link Capacity, IEEE J. Select. Areas Comm., Vol. 12, No. 8, Oct. 1994, p.1281-1288.


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station.

b. Outdoor penetration loss

No penetration loss is applied on outdoor environment.

c. Vehicle penetration loss

It is the degradation of the RF signal caused by an enclosure of vehicle.

Log-normal Fade Margin (dB) is defined at the cell boundary for isolated cells. This is the margin

required to provide the specified coverage availability over the individual cells. In Samsung link budget the

log-normal fade margin with 95% area coverage and 9 dB shadowing standard deviation is applied. Note

that 95% area coverage probability can be regarded as 87.3 % cell edge coverage probability, alternatively.

Figure 5 shows the log-normal fade margin with 9 dB standard deviation to the coverage probability at the

cell edge.

Cell-Edge Coverage (or Small Area Coverage)

PDF of

=

2

2

2

)(exp

2

1)(

xxxp

Coverage = 1 outage

[ ]

=

==

22

1

2

1

)()(

0

00

0

xxerf

dxxpxxPRPx

x

Fade Margin = xx 0

where,

: Received signal strength (log-normal distribution) [dBm]

x : Mean of Log-normal distribution v(median value) [dBm]

0x : Receiver threshold [dBm]

: Shadowing log normal standard deviation

[Note] Coverage: fraction of the locations at r = R wherein a mobile would experience a received

signal above threshold.


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0

5

10

15

20

25

0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

coverage probability at cell edge

Log-normalfadingmarg

in(dB)

F igure 5. Log-normal fading margin(dB) according to coverage probabil ity at cell edge(std.= 9 dB)

Maximum Allowable Path Loss (dB) is the maximum tolerable mean path loss in the link. In other words,

this is the largest value that the mean path loss can achieve such that the mobile and base station will still

have enough power to close the link. The path loss is specified as a mean path loss since most propagation

prediction algorithms do not consider the effects of slow fading and therefore generate mean predictions.

The maximum allowable path loss is calculated with receiver sensitivity, i.e., minimum received signalpower, and maximum transmitted EIRP.

Cell Radius (km) is the cell coverage. Cell coverage can be defined to the region satisfying minimum

received signal level and signal quality required to obtain the performances of optimal system. In other

words, cell coverage can be defined as the range of distance separation between base station and mobile in a

certain location where the received signal exceeds minimum received signal level. This distance is

determined by using maximum allowable path loss and propagation model. In Samsung link budget a

Modified HATA model is applied to estimate cell radius. As an example, Path loss to the distance evaluation

using Modified HATA model is drawn in Figure 6.


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Mo di f ied Hata M o de l at 889 MHz / U rban

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5

Distanc e [ km]

PathlossdB]

F igure 6. Path loss vs. distance at 889 MHz when Modif ied HATA model is appli ed for propagation model

2.2 Reverse link

Test environment

RF test environments are same as those in the forward link. Details are described in Section 2.1 for forward

link.

MS maximum power per traffic channel (dBm) is the maximum transmitting power per traffic channel

by MS. It depends on type of mobile. A typical value is about 23 dBm.

MS antenna gain (including body loss, etc.) (dBi) is the total gain affected by the MS receiver antenna

gain (dBi), receiver system loss (-dB) and body loss (-dB). A typical value of receiver system and body

losses are 0 dB and 3 dB, respectively.

MS transmitter EIRP per traffic channel (dBm) is the effective MS transmitting power in traffic channel.

It is calculated by the summation of BS maximum transmitter power per traffic channel (dBm), transmissionsystem losses (-dB), and the transmitter antenna gain (dBi).

BS receiver antenna gain (dBi) is the maximum gain for the receiver antenna in the horizontal plane and it

is specified as dB relative to an isotropic radiator.

BS cable and connector losses (dB) are the combined losses of all transmission system components

between the transmitter output and the antenna input. Note that all losses in positive dB values in link budget

table. A typical value is 3 dB.

Thermal noise density (dBm/Hz)

Details are described in Section 2.1 for forward link.


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Receiver Noise Figure(dB)

Details are described in Section 2.1 for forward link. 3 dB is estimated for Samsung system.

Loading factor (%) is the ratio of realistic maximum traffic users to Pole capacity, which is inversely

proportional to interference. This indicates the change of the user traffic. In general, 50% loading in reverselink is assumed in order to balance reverse and forward link capacity.

Interference margin (dB) is necessary to use in the reverse link budget since the loading of the cell, the

loading factor, affects the coverage. The more loading is allowed in the system, the larger is the interference

margin required in the reverse link, and the smaller is the coverage area. The relation between interference

margin (I .M) and loading factor (X) is as follows:

IocIscNIocIsc

NNX

th +++==

max

X

NIocIsc

IocIsc

NIocIsc

NN

NIocIscMI

thth

thth

th

=

++

+

=

++

=++

=1

1

1

11..

)1log(*10).(. XdBMI =

where,maxN : pole capacity

Isc: same cell interference density

Ioc: other cell interference density

thN :thermal noise density

For example, loading factors (cell loading) are 50% (= 0.5) and 70% (= 0.7), then, interference margin is 3dB

5.23dB, respectively.

Total effective noise and interference density (dBm/Hz)


Information rate(dB-Hz)


Required Eb/(No+Io) per antenna (dB) is the ratio of the required energy per bit to interference power

spectral density for a good quality on reverse link. In Samsung link budget, the simulation resulted from

3GPP2 contribution for both voice and data.services are adopted. The 1% and 5% target FER for voiceservice and data service, respectively are chosen.


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Receiver sensitivity (dBm)


Log-normal fade margin (dB) ,

Detail descriptions are in Section 2.1 for forward link. Note that the different combining methods are used in

forward and reverse link. A 95% area coverage and 9 dB of standard deviation are applied in Samsung linkbudget.

Handoff gain (dB) Detail descriptions are in Section 2.1 for forward linkThe following table shows the

handoff gains used in Samsung reverse link budget. They are obtained from the simulation.

Condition 95 % area coverage probability with 9 dB std. of fading

Service type Voice Data (153.6 kbps)

Channel model Pedestrian Vehicle Pedestrian VehicleGeometry (dB) 0 4 0

Handoff gain (dB) 4.45 0.15 0.32

The above table indicates that handoff gain in data service is smaller than that of voice service, since total

received power at MS in case of data service is lower than voice case due to the path difference to the MS

from each BS in serving cell and target cell. Penetration loss (dB) is the required margin to overcome the loss due to car and building

Detail descriptions are in Section 2.1 for forward link

Maximum allowable path loss (dB)


Cell radius (km)



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3. Examples of Link Budgets

3.1 1X Forward link Voice

3.2 1X Forward link data


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3.3 1X Reverse link voice

3.4 1X Reverse link data

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