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8/2/2019 6 Dyed Csawg

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Satellite Link Impairment due toRain and Other Climatic Factors

Syed Idris Syed Hassan

Sch of Electrical & Electronic Engineering

Engineering CampusUniversiti Sains Malaysia

Seri Ampangan, Nibong Tebal

14300 Penang, Malaysia


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Introduction

Rain attenuation is a major constraint in

microwave radio link design above 10 GHz.

Several empirical and non-empirical rainattenuation prediction models that have been

developed are based on the measured data

obtained from temperate regions . Most of these existing rain attenuation

prediction models do not appear to perform

well in high rainfall regions.


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Introduction (continuation)

The ITU-R [4] model is currently being widely used by

many researchers.

Cumulative distribution empirical evidence shows thatthe ITU-R model underestimates the measured rain

attenuation cumulative distribution when applied to

tropical regions, leading to a poor prediction.

Other impairments are due to gaseous absorption,

cloud, tropospheric refractive effects, scintillation, wet

antenna etc.


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Measurement of bit error rateduring cloudy and clear sky


5/34

Teleconference between USM andNIME via Superbird C


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Theoretical

Rain attenuation

ScintillationCloud attenuation

Gaseous attenuation


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Rain attenuation model

ITU

Lognormal

Moupfouma SAM

Yamada

Lin

DAH

Assis

Flavin CETUC

Crane

Etc..


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ITU model

The specific attenuation, is a function of therainfall rate, R0.01 exceeded at 0.01% of time is

given by:

= k(R0.01

) dB/km

where kand are frequency and polarization

parameters, given by ITU-R recommendation


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ITU rain attenuation prediction modelat 0.01% of time exceeding

Specific Rain Attenuation

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70 80 90 100

Frequency (GHz)

Spec.Atten.

dB/km

horizontal polization

vertical polization

Ka-bandKu-band

Spec. attenuation

For Ku-band

4-7dB/kmFor Ka-band

12-25dB/km


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Models and measurement


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Rain Rate Models(compared with measurement)

Rain rate at 0.01%

Mea =112.6 mm/h

ITU =120 mm/h

Crane/Gamma=148mm/h

Log =100mm/h

R-H=135mm/h

Bod=55mm/h

DD= 28mm/h

7.3501.0 =A

0

50

100

150

200

250

300

0.001 0.01 0.1 1

percentage,%

rainrate,mm/h

ITU

Crane

DDMoupfouma

Bodtman&Ruthroff

Rice-Holmberg

Log-normal

Gamma

USM(3 years avg)


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Worth month Vs Annual rain rate probability

Pa = 0.509(Pw)x1.2

r2 = 0.9731

Pa = 0.2965(Pw)1.1623

00.05

0.1

0.15

0.20.25

0.3

0.35

0.4

0 0.5 1

worst month average rain rate

exceedence,Pw( %)

annualaverage

rainrate

exceedence,

Pa(%)

Measured

ITU

Power (Measured)

Power (ITU)

Measurement:

Pa= 0.509(Pw)1.2

ITU :

Pa =0.2965(Pw)1.1623


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Attenuation model at 0.01%

Mea=30dB

ITU= 15.34dB

Moupfo=31dB

DAH= 27dB

Crane=23dB

Flavin=19dB

SAM=20dB

VIHT=16dB

Gracia=10dB

0

10

20

30

40

50

60

0.001 0.01 0.1 0.3 1

percentage, %

attenuation,d

B

USM(3 years avg)

DAH

VIHT

Crane

ITU

SAM

Moupfouma

Gracia-Lopez

Flavin


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Current Experimental SetupMeasurement Site USM KMITL ITB

Earth Station Location 5.170N

100.40E

13.70N

100.80E

6.50S

107.40E

Beacon Frequency,

(GHz) 12.255 12.74 12.247

Antenna Elevation (deg)40.1 54.8 64.7

Altitude (m) 57 40 700

Antenna

Diameter (m)2.4 2.4 1.8


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Developing a new Rain attenuation modelfor Ku-band

Modify ITU-R model to retain the concept of an

equivalent rain cell.

The horizontal projection of the slant path, LG

was

modified based on the rain height, elevation angle,

reduction factor, and the rainfall rate at the

measurement sites.

The model was revised, so that it can be used attropical countries with the antenna elevation angle

varying from 400 to 700 .


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Comparison ITU model with measured dataand proposed model at USM at Ku-band

0

5

10

15

20

25

30

35

40

45

50

0.001 0.01 0.1 1

Percentage of time %

Rainfalla

ttenuationd

B

USM

ITU

95% UL

95%LLproposed model

UL = Upper Limit ;

LL = Lower limit

(confidence interval)


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Comparing ITU model with measured dataand proposed model at KMITL at Ku-band

0

5

10

15

20

25

30

35

40

45

50

0.001 0.01 0.1 1


Rainfalla

ttenuation

dB

KMITL

ITU

95% UL

95%LL

proposed model


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0

5

10

15

20

25

30

35

40

0.001 0.01 0.1 1


Ra

infalla

ttenuation

dB

ITB

ITU

95% UL

95%LL

proposed model

Comparing ITU model with measured dataand proposed model at ITB at Ku-band

Comparing the errors between ITU and


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Comparing the errors between ITU and

proposed model

%rms

% error

KMITL

P% 0.001 0.003 0.01 0.03 0.1 0.3 1

% error

USM

ITU -27.9 -18.1 -6.4 0.4 6 9.1 -26.4 16.2

Proposed -5.1 -2.4 0.05 1.1 4.32 4.17 8.19 2.9

ITU -40.3 -33.4 -23 -18.1 -12 -15.1 -41.3 28.4

Proposed -6.09 -3.63 -0.49 -1.46 5.78 1.94 5.81 4.11

% error

ITB

ITU -35.5 -29 -23.3 -17.9 -22 -18.3 -48.1 29.9

Proposed 9 6.19 -0.11 -4.92 -5.4 -1.56 6.79 6.14


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Specific Attenuation contour mapping

for 12 GHz (horizontal polarization)


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Specific Attenuation contour mappingfor 12 GHz (vertical polarization)


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Scintillation at slant path of 41O

Scintillation ofabout 0.2-0.4 dB

occurred at

frequency 12GHzaccording to months

and seasons


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Comparison of the measured scintillation

spectrum with the theoretical pattern (straightline).


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Cloud attenuation

Gunn and East model

Liebe model

Staelin model

Slobin model-derived from Staelin model

Altshuler model


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Gunn and East model

Cloud attenuation is given by

( )kmdBd /21

Im

6

4343.0 1

+

=

where

= complex relative dielectric constant of water=wavelength (cm)d=density of water (g/cm3) (~0.99)

1=liquid water content of the cloud (g/m3

)Im=imaginary part

Li b d l


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Liebe model

The cloud attenuation is given by( )kmdBffN /)("182.0=

( ) ( ) ( )[ ] 121 1"29"

+= yfN

( )( )

( )

( )( )

( )2

21

2

1

11

"s

s

p

po

ff

ff

ff

fff

+

+

+

=

( ) "2' +=ywhere

f= frequency in GHz

15.273

300

+= T

( ) ( ) ( ) 2221

2

1

11'

++

++

=

sp

o

fffff

( )11500590 = sf

( ) ( )2129414.14209.20 += pf

( ) ( )13.10366.77 += To

51.32 =

48.51 =

T in Centigrade


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Staelin model

The cloud attenuation is given by

( ) ( )kmdBT

/16.110343.42

2910122.01

1

=

where 1= the liquid water density of the cloud (g/m3)

T=temperature (K)

=wavelenght (cm)


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Slobin model

Make use of Stelin model and divide the

cloud into 12 different categories such as

lightest cloud, light cloud, medium cloud,

heavy cloud and heavier cloud.


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Altshuler model

Cloud attenuation at 10oC is given by

( ) ( )kmdB /3.11403.000075.00242.0 115.1 +

++=

= wavelength in mm

1=surface absolute humidity(g/m3)

Total attenuation is obtained by multiplying the distance below

where

( ) ( ) csc=DFor >8o

( ) ( ) ( )[ ] ( ) sincos2/1222

eeee aahaD +=For< 8o

=elevation angle

e=effective radius of the earth (8497km)

he=6.35-0.302 effective cloud height (km)=surface absolute humidity (g/m3)

where


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Gaseous attenuation

Water vapor AW

Oxygen Ao

Total Gaseous absorption (dB) is

owg AAA +=


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Water vapor attenuation

o

www fordBhA 10sin/ >=

( ) oweweww fordBhRFhR

A 10/tan

cos

=

w =specific attenuation of water vapor (dB/km)R

e

=effective earth radius (8500km)

= elevation anglehw= equivalent height of water vapor


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Oxygen attenuation

o

ooo fordBhA 10sin/ >=

( ) ooeoeoo fordBhRFhR

A 10/tan

cos

=

o =specific attenuation of oxygen layer (dB/km)R

e

=effective earth radius (8500km)

= elevation angleho= equivalent height of oxygen layer


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Future research

To verify the attenuation models at Ka-band

Develop a new attenuation model for Ka-

band USAT application in teleconference and

telemedicine


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