Aalto University School of Electrical Engineering ELEC ... · Engineering ELEC-E4750 Radiowave...

Aalto University School of Electrical Engineering

ELEC-E4750 Radiowave Propagation and Scattering Session 6: Terrestrial and Satellite Links

ELEC-E4750 20.10.2016

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Books, Topics and Exercises §  Books

§  Main books §  S. Saunders, Antennas and Propagation for Wireless Communication Systems, Chapters 3, 5,

6-8, 10, 12 15, Wiley. §  H. L. Bertoni, Radio propagation for modern wireless systems, Chapters 2-6, Prentice Hall. §  A. . Molisch, Wireless Communications, Chapters 1, 5 and 8, Wiley. §  John A. Richards, Radio wave propagation, an introduction or the non-specialist, Chapter 3,

Springer. §  Hardcover or paperback copies of both books are available in AaltoELEC and main

library. §  Supplemental books:

§  D. M. Pozar, Microwave Engineering, Chapter 1, Wiley.

§  Topic 5: Terrestrial links (Ch. 5 and 6, Ch. 4) §  Exercise 1: Two-ray multipath model §  Exercise 2: Tropospheric propagation

§  Topic 6: Terrestrial and satellite links (Ch. 7) §  Exercise 1: Sky waves §  Exercise 2: Rain attenuation

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Schedule

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Wk Date Location New topics, lectures and deadlines

37 Tue. 13 Sep. R037/TU3 1194-1195 Introduction; Topic 1: prerequisite Thu. 15 Sep. R037/TU6 1200-1201 Clicker lecture 1

38 Tue. 20 Sep. R037/TU3 1194-1195 Topic 2: reflection and transmission Thu. 22 Sep. R037/TU6 1200-1201 Clicker lecture 2

39 Tue. 27 Sep. R037/TU3 1194-1195 Topic 3: diffraction Thu. 29 Sep. R037/TU6 1200-1201 Clicker lecture 3

40Tue. 04 Oct. R037/TU3 1194-1195 Topic 4: scattering and two-ray model; Thu. 06 Oct. R037/TU6 1200-1201 Clicker lecture 4

41 Tue. 11 Oct. R037/TU3 1194-1195 Topic 5: Terrestrial links Thu. 13 Oct. R037/TU6 1200-1201 Clicker lecture 5; threshold deadline of

topics 1-4

42 Tue. 18 Oct. R037/TU3 1194-1195 Topic 6: Terrestrial and satellite links Thu. 20 Oct. R037/TU6 1200-1201 Clicker lecture 6

•  Clemens and Suzan will lead on 04, 06 and 11 Oct. •  Usman is away for 25.9-29.10.



Atmosphere Around Earth’s Surface

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Q1a:Whichoneiscorrect?A.  Troposphereis6andIonosphereis1and2.B.  Troposphereis5and6,andIonosphereis3.C.  Troposphereis6andIonosphereis3.D.  Troposphereis5and6,andIonosphereis1and2.

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1

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Q1b:Whichoneiscorrect?A.  Troposphereis6andIonosphereis1and2.B.  Troposphereis5and6,andIonosphereis3.C.  Troposphereis6andIonosphereis3.D.  Troposphereis5and6,andIonosphereis1and2.

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Tropospheric Refraction

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Earth radius = R

h 1α1θ

2θ2α2n

1n

Refractiveindex =

Refractive index =

Launched ray

0 100 200 300Refractive index in N-unit [ppm]

0

1000

2000

3000

4000

5000

6000

7000

Hei

ght a

bove

the

grou

nd [m

]

ni = c0 εiµ

n1 sinθ1 = n2 sinθ2



Ionosphere

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… is a region of ionized plasma; ions are trapped in the Earth’s magnetic field.

Electromagnetic radiation of the sun makes the ionization.



Ionosphere Effects on Radio Propagation

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•  Key parameter: electron concentration per cubic meter N�

•  The electron concentration influences the refractive index:

n02 =1− fc

f"

#$

%

&'

2

fc = 8.9788 N [Hz](Critical frequency)


A.  Atthecri;calfrequency,therefrac;veindexisalmost0.B.  Refrac;veindexissmalleratnightthaninadayinionosphere.C.  Radiowavesfromthegrounddonotpenetratethe

ionospherebelowthecri;calfrequency.D.  Thedensestioniza;onleadstohighercri;calfrequency.

Q2a:Whichstatementiswrong?

n02 =1− fc

f"

#$

%

&'

2

fc = 8.9788 N [Hz]



Rain Attenuation•  Which level of rain attenuation is most problematic for

satellite links?

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3112 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 11, NOVEMBER 2003

Fig. 2. CDF of measured and predicted rainfall rates .

Fig. 3. Measured and predicted rain attenuation over a period of 12 mo from February 1999 to January 2000.

the attenuation computed on the basis of the model given in [8]is more pronounced at lower probability levels. Themodel givenin [8] was validated against the data recorded at 22 and 38 GHz.Therefore, the experimental results appear to indicate that fur-ther research is necessary to characterize the attenuation due torain at higher millimeter wave frequency bands over longer pathlengths. This, however, requires a comprehensive set of mea-surements over several years for more than one link operatingat different millimeter wave frequencies.

B. Analysis and Modeling of Rain Fade Durations

Currently, there is an increasing interest in the duration offade events in order to develop a model from which the numberof events with fades of a given depth and given duration may be

predicted, to help system designers to assess the likely periods ofsystem unavailability to optimally design communication sys-tems that handle coded massages over defined bandwidths.The degradation of path loss below a certain level can be

caused by either many events of short duration, or conversely,few events of long duration. From long-term cumulative dis-tribution function, it can not be determined whether the per-centage of time a given level of attenuation exceeded was dueto many events of short duration or few events of long dura-tion. Therefore, statistical analysis of path loss requires not onlythe long-term probability of exceedance of a level (yearly orworst-month probability) but statistics of duration of fades aswell. Hence, if it is known that how long a certain level of fadingis likely to last on average, then a decision can be made to takeaction or wait for the signal to recover.

Khan et al., TAP 2003.�


Q3a:Whendiscussingtheraina9enua:on,weusuallycarearainfallrateof

A.  Thesmallest1%valueofayear.B.  Ameanvalueofayear.C.  Amedianvalueofayear.D.  Thelargest1%valueofayear.


Q3b:Whendiscussingtheraina9enua:on,weusuallycarearainfallrateof

A.  Thesmallest1%valueofayear.B.  Ameanvalueofayear.C.  Amedianvalueofayear.D.  Thelargest1%valueofayear.



Outage Probability due to Rain Attenuation

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L0.01 = aR0.01b s0.01rR

•  Heavy rain fall rate produces the most severe outage.�3112 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 51, NO. 11, NOVEMBER 2003

Fig. 2. CDF of measured and predicted rainfall rates .

Fig. 3. Measured and predicted rain attenuation over a period of 12 mo from February 1999 to January 2000.

the attenuation computed on the basis of the model given in [8]is more pronounced at lower probability levels. Themodel givenin [8] was validated against the data recorded at 22 and 38 GHz.Therefore, the experimental results appear to indicate that fur-ther research is necessary to characterize the attenuation due torain at higher millimeter wave frequency bands over longer pathlengths. This, however, requires a comprehensive set of mea-surements over several years for more than one link operatingat different millimeter wave frequencies.

B. Analysis and Modeling of Rain Fade Durations

Currently, there is an increasing interest in the duration offade events in order to develop a model from which the numberof events with fades of a given depth and given duration may be

predicted, to help system designers to assess the likely periods ofsystem unavailability to optimally design communication sys-tems that handle coded massages over defined bandwidths.The degradation of path loss below a certain level can be

caused by either many events of short duration, or conversely,few events of long duration. From long-term cumulative dis-tribution function, it can not be determined whether the per-centage of time a given level of attenuation exceeded was dueto many events of short duration or few events of long dura-tion. Therefore, statistical analysis of path loss requires not onlythe long-term probability of exceedance of a level (yearly orworst-month probability) but statistics of duration of fades aswell. Hence, if it is known that how long a certain level of fadingis likely to last on average, then a decision can be made to takeaction or wait for the signal to recover.

Khan et al., TAP 2003.�

R0.01

s0.01 =1

1+ rR sinθ35exp(−0.015R0.01)

Correction factor�

1 % most severe rain attenuation



Rain Attenuation and Path Length

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… is proportional to total rainy slant path length rR.�

rR =hR − hSsinθ

The effective rain height hR varies

for latitude.

The length rR depends on local cloud distribution.



Depolarization due to Hydrometeor

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Attenuation depends on the polarization direction with respect to orientation of the hydrometeor.

XPD proportional to rain attenuation loss, XPD = 35.8−13.4 log10 L(Reasonably accurate above 10GHz)


Q4a:whichstatementiswrong?

A.  RainaKenua;ondependsontheradiofrequency.

B.  Loweleva;onsatellitepathisinfluencedbymorerainaKenua;onthanhigheleva;onsatellitepath.

C.  RainaKenua;onispolariza;on-selec;ve.

D.  Greaterlinkmarginisrequiredinthemildclimateareasthanintropicalareas.


Q4b:whichstatementiswrong?

A.  RainaKenua;ondependsontheradiofrequency.

B.  Loweleva;onsatellitepathisinfluencedbymorerainaKenua;onthanhigheleva;onsatellitepath.

C.  RainaKenua;onispolariza;on-selec;ve.

D.  Greaterlinkmarginisrequiredinthemildclimateareasthanintropicalareas.



Improving the Outage - Diversity

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Rain cell sizeRain cell size

ff

f


Q5a:whichoneisrightastothediversityinsatellitelinks?A.  Useofmul;pleradiofrequencies

areaseffec;veashavingmul;plegroundsta;onstoaKainlinkdiversity.

B.  Asecondgroundsta;onplacedjustnexttothefirstgroundsta;onleadstolowcorrela;onofrainaKenua;onbetweenthetwolinks.

C.  Ifcorrela;onofrainaKenua;onbetweentwolinksislow,thereisnoimprovementofoutage.

D.  Twogroundsta;onsmustbeseparatedmuchgreaterthantheaverageraincellsizeofthesitetoleveragediversityefficiently.



Contact Sessions for Topic 6•  Learning outcomes of the present exercise problems are to

–  Be able to explain the difference of refractive propagation in troposphere and ionosphere (problem 1)

–  Be able to utilize practical tools for estimating the rain attenuation (problem 2)

•  During the contact sessions, you are –  solving the exercise problems by referring to relevant parts of the

course books. •  A limited number of course books are available in the room.

–  encouraged to discuss with other students and teachers. –  asked to contact teachers once your solutions are ready.

•  If you prepare exercise solutions in an electronic format (recommended), upload the solution to MyCourses first and then contact teachers.

–  asked to propose points for your ready solutions to the teachers. –  not given exercise points without discussing with teachers.

•  The discussions MUST happen in the contact sessions. –  reminded that the deadline of Topic 5-8 exercises is November 17th.

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