2.2 CDMA Link Buget

Internal Use Only▲

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CDMA

Presented by: AuthorCDMA DivisionZTE Corporation

Mobile: E-mail:

Presented by: AuthorCDMA DivisionZTE Corporation

Mobile: E-mail:

Link Budget


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OutlineBasic conception of link budget

Reverse link budget in CDMA 2000 1X

Forward link budget in CDMA 2000 1X


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OUTLINE

Basic concept of link budgetBasic concept of link budgetBasic concept of link budget

Reverse link budget in CDMA2000Reverse link budget in CDMA2000Reverse link budget in CDMA2000

Forward link budget in CDMA2000Forward link budget in CDMA2000Forward link budget in CDMA2000


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What is Link BudgetUnder condition of ensuring the service quality, confirm the Maximum Allowable Path Loss of the propagation environment between BTS and terminals.

To predict coverage radius using link budget

Figure out numbers of sectors to meet coverage requirement

building

HataCost231

Correction model

…

HataCost231

Correction model

…


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The constitution of wireless link

Receiver

antenna

antenna

Transmission line

Transmitter

Transmission line

Transmit Power

Loss of transmission line

Gain

Path loss

Gain

Loss of transmission linesensitivity

Margin


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Link Budget Model

Up link

Down link

mobile BTSFeeder loss

Antenna gain

Path loss

Antenna gain

Feeder loss margin

Margin：Fade margin、Interference margin、Penetration loss…

Margin：Fade margin、Interference margin、Penetration loss…


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Transmitter

)()()(

)()(

dBLossorBodyfeederdBiternOfTansmitAntennaGai

dBmerTansmitPowdBmRPTransmitEI

−+

=


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Receiver

)()()/(

)/()(

HzdBDataRatedBreqNoEb

HzdBmceNoiseInterferendBmitivityceiverSensRe

−++=


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Penetration Loss

Main mechanism：

diffraction, refractionCalculation method：statistic

Building lossCar loss

?

?

?

Typical value of Building Penetration Loss

Dense urban

Urban

Sub urban

Rural

25 dB

20 dB

15 dB

6 dB

Open land 0 dB


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Fade margin

90%

75%

Assuming that at least 75% of edge area (90% in cell) can reliably receive signal strength more than -105dBm. Standard Deviation is generally 8 dB.From the table we can find that 75% Probability corresponds to 0.675σ

0.675 x 8 = 5.4 dB-105 + 5.4 = -99.6 dBm

Therefore, The designed middle value should be -99.6 dBm

Deviation to middle value signal strength M

Accumulated normal probability distributing

0%10%20%30%40%50%60%70%80%90%

100%

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

75%

0.675σ

Are

a

Pro

babi

lity

dens

ity

-99.6dBm

σ=8dB

RSSI

Normal Distribution0.675σ=5.4 dΒ

- 105 dBm

[ ]dxxxPP mx

xx 2

2

0

0 2)(

21

0 exp][σπσ−−

∞

∫=≥=


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OUTLINE


Reverse link budget inCDMA2000Reverse link budget inCDMA2000Reverse link budget inCDMA2000

Forward link budget inCDMA2000Forward link budget inCDMA2000Forward link budget inCDMA2000

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CDMA 2000 1X System 800M Reverse link budget


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Explanation for link budget (1)

service rate：Use to show the voice service and data service system can support, at present, Radio Configuration in CDMA2000 1X is RC3, so in reverse link ,it can support 9.6kbps，19.2kbps，38.4kbps，76.8kbps，153.6kbps.

MS EIRPCDMA terminal’s maximum TX power is 0.2W, 23dBm

MS antenna gainCDMA mobile’s antenna gain is 0 dB，and fixed terminal (in door or out doot) has its relative gain.

Body lossMost of the time body loss is 3 dB，IF it is fixed terminal or data service，we could consider that mobile a little far from body, and body loss can be 0dB.


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common antenna gain

11dBi7360Single

16.5dBi6.590Dual

18dBi765Dual

1.9G

11dBi8360Single

15.5dBi1090Single

17dBi1065Single

800M

10dBi10360Single

Single

15.5dBi1765Dual

450M

Gain Vertical beamwidthHorizon beamwidthPolarization


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Explanation for link budget (3)BS feeder loss

When the length from BTS to antenna is less than 15m, usually only 1/2 inch Jumper cable is required. Meanwhile there is only jumper cable loss.

If 7/8 inch feeder cable is also used, we needs to take 7/8 inch feeder loss into consideration. When cable is longer than 80m, we consider it’s too long, it’s better to use 5/4 inch or other big size feeder.

Antenna

1/2“Jumper

7/8“Cable

Grounding Clip

1/2“Jumper

Cabinet

LighteningArrester Grounding Clip


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Eb/N0Eb/N0 is demodulation SNR which reverse link requires when system is unload。In practical system, the Eb/N0 required is different in different frequency band, different wireless environment, different terminal characteristic, different RC, different frame error rate. Minimum Performance testing standard provides Eb/N0 at a high FER and a low FER, If Eb/N0 of other FER is required，figure it out by linear interpolation.The table below is from standard:

4.5 @ 6.1 dB9.0 @ 5.5 dB12002.5 @ 6.1 dB7.5 @ 5.5 dB24000.9 @ 6.1 dB5.5 @ 5.5 dB48000.3 @ 6.1 dB3.5 @ 5.5 dB9600

5

14.0 @ 6.5 dB22.0 @ 5.9 dB120012.0 @ 6.5 dB23.0 @ 5.9 dB24002.2 @ 6.5 dB7.6 @ 5.9 dB48000.3 @ 6.5 dB2.8% @ 5.9 dB9600

0, 2, 3, 5, 7, and 9

B

At Upper Eb/N0At Lower Eb/N0FER Limits (%)

Data Rate (bps)Band ClassesCase


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Interference MarginThis value is related to System Loading.

The formula is：

In CDMA 2000 1X system, generally loading factor is 75%。

)1(-10logmargin einterfernc 10 systemload−=


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soft hand-off gainSoft hand-off provides forward traffic channel multi-path diversity at the edge of BS, improves channel’s ability of anti-fading, decreases mobile’s Tx power, thereby decreases mobiles' interference to system, and extra gain to reverse link coverage.In CDMA system, soft hand-off gain’s concrete value is related to correlation coefficient ρof two propagation path, normal fading variance σ, edge coverage rate Prel.

4.670.50.98

4.20.50.95

4.090.50.9

3.70.50.75

Soft hand-off gain(dB)

σ=8dBρPrel


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Edge Coverage probability of serving areaThere are relationship between edge coverage probability and area coverage probability. The concrete relationship is as follows: In the chart the left y-axis is the area coverage probability, right y-axis is edge coverage probability, and x-axis is the standard deviation/ index of path loss. example：path loss index: n=4 (complex propagation environment), standard deviation=8dB, edge coverage rate=75%, corresponding area coverage probability will be 94%; path loss index n=2 (free space), standard deviation=8dB,edge coverage rate=75%, corresponding area coverage probability will be 91%.


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Antenna HeightGenerally antenna height is lower in dense urban area with

large capacity, to reduce pilot pollution and interference to other cells.

In open area with the capacity distributes dispersible, antenna height will be higher, and cover lager area.

Recommended Antenna height values are as follows: dense urban: 30m, urban: 40m,suburban and rural: 50m.


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>19.2 kbps>38.4 kbps

>153.6 kbps

>76.8 kbpsdistance

subscribers

>9.6 kbps


antenna heightIn same environment, the faster the speed of data rate is, the smaller the coverage

radius 1X system can provide is.Comparing with voice service, high speed data service’s coverage radius is smaller,

but generally the capacity is key restricted factor, especially in urban environment. So BTS’s actual coverage radius is smaller than coverage prediction, and the coverage radius that data service provides in 1X system can also approach the actual radius BS provides.


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EVDO (RLS 0) Reverse link budget related

Structure of link budget table is the same as data service part of CDMA 1X

Name of Parameters changedMobile station :MS—>access terminal :AT

Frame error rate FER—>package error rate:PER

Value of parameters Demodulating threshold Eb/No is different from CDMA

1X，but it is simuliar with CDMA 1X

Body loss is 0dB


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OUTLINE


Reverse link budget in CDMA2000Reverse link budget in CDMA2000Reverse link budget in CDMA2000

Forward link budget inCDMA2000Forward link budget inCDMA2000Forward link budget inCDMA2000


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CDMA 2000 1X system 800M forward link budget


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Explanation (1)

The maximum Tx power per traffic channel in one BTSThis value is in direct ratio with rated transmit power of the BTS.In RC3 configuration, when system parameters are default. The maximum Tx

power per traffic channel (voice) accounts for the total output 7.46%, approximate 31.47dBm, under the condition of two legs.

In 8X and 16X data rate system, The upper limit of Supplemental channel’s Tx power accounts for total output power 25% ,approximate 36.99dBm.

In 2X and 4X data rate, The upper limit of Supplemental channel’s Tx power accounts for total output power 19.9% ,approximate 36dBm.

trafftrafpagPsyncpiltotal PMKPNPPP α+++=pilP

syncP

pagP

trafP

pN

M

fα

trafK

Power of pilot channel；

Power of sych channel ；

Power of paging channel；

Power of traffic channnel；

Channel number of active paging channel；

channel number of active traffic channel；

Forward link voice activation factor；

Forward link power control factor


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Explanation (2)

interference factor of other cellsForward link interference includes two parts: interference of local cell and of other cells.Because CDMA’s forward link channel is orthogonalized by Walsh code, in ideal situation, interference from local cell is 0, but multi-path results in incomplete orthogonalization of other channels, which increases interference, and it becomes the main interference gradually when mobile station is getting closer to Base station.The interference from other cells becomes the main interference gradually when mobile station is getting closer to the edge of cell, it is also the interference we calculated in forward link budget.


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A sample of EVDO forward link budget


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EVDO link budget explanation—Terminology

Demodulation threshold—Required Îor/No for each antennaDual antennas terminalÎor and No are both power spectrum density, custom usage for DO, it can be converted to Eb/Nt.

Rx Diversity GainUnder the same condition of download bitrates, target PER, the antenna’s demodulation threshold Îor/No required by dual antenna terminal is lower than that of signal antenna terminal.According to ZTE shield room’s test result, the gain is approximately 5~6dB

Package Error Rate—PERMulti-user Diversity Gain

The gain of forward throughput of sectors with multiple active users to those with single active user is correlate with forward dispatch algorithm.According to outdoor testing result, the gain is 2dB


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Single & dual antennaSingle antennaforwardTerminal types

38.4kbps~2.4Mbps, 9 classes

9.6kbps~153.6kbps, 5 classesforwardClass of forward

bitrates

Forward

Forward & reverse

Forward& reverse

Link

yesnoMulti-uses diversity gain

differentDemodulation threshold

0dB3dB（voice）0dB（data）

Body loss

EVDO1XItems

EVDO link budget explanation—difference from 1X

2.2 CDMA Link Buget

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