transmission planning mod 1

8/14/2019 Transmission Planning MOD 1

1/50

Section 1 - Module 1 - Page 13FL 42104 AAAA WBZZA Edition 2 - July 2005

All rights reserved 2005, Alcatel

- RADIO NETWORK PLANNING

1.1 Introduction to Network Planning3FL 42104 AAAA WBZZA Edition 2 - July 2005

Network Planning


2/50


Network Planning - Introduction to Network Planning

All rights reserved 2005, Alcatel- RADIO NETWORK PLANNING

1 - 1 - 2

Blank Page

This page is left blank intentionally


3/50




1 - 1 - 3

Objectives

To be able to describe concepts such as:

Polarization

Frequency plansAntenna parameters

Free space loss


4/50




1 - 1 - 4

Blank Page



5/50




1 - 1 - 5

Table of Contents

Switch to notes view! Page

1 Electromagnetic waves 7Electromagnetic waves 8

Exercise 9Blank Page 10

2 Polarization 11Polarization 12Exercise 13Blank Page 14

3 Electromagnetic spectrum 15Electromagnetic spectrum 16

4 Radio spectrum 17Radio spectrum 18

5 Use of the spectrum 19Use of the spectrum 21Blank Page 22

6 General characteristics on the ITU-R recommended frequency plans23General characteristics on the ITU-R recommended frequency plans 26

7 Antenna System 27Antenna System 36Exercise 37Blank Page 38

8 Field strength and related parameters 39Field strength and related parameters 41Blank Page 42

9 Free space loss 43Free space loss 44Exercise 45Blank Page 46

10 Radio Network Design procedure 47

Radio Network Design procedure 48Radio Network Design procedure 49End of Module 50


6/50




1 - 1 - 6

Table of Contents [cont.]



7/50




1 - 1 - 7

1 Electromagnetic waves


8/50




1 - 1 - 8

TEM Wave


Electromagnetic waves

Electromagnetic Waves

An electromagnetic wave is a simultaneous interaction between an electrostatic (E) field and a magnetic (H)field.

Radiated energy from an antenna, once a distance from the source, forms E and H fields, which areperpendicular to each other and to the direction of propagation and are hence referred to as TransverseElectro-Magnetic (TEM) waves.

Frequency, Wavelength and Velocity

Wavelength is the distance in meters between any two similar points on the wave. This portion ofthe wave is referred to as one complete cycle.Wavelength is given symbol .

Frequencyf is the number of complete cycles passing a fixed point in one second.If one cycle passes a fixed point in one second this corresponds to a frequency of 1 Hertz (Hz).

In free space thevelocityof an EM wave is approximately 3 x 108 ms-1. This is the speed of light(since light is an EM wave) and is usually given symbol c.The relationship between c (velocity), f (frequency) and (wavelength) of an EM wave is given bythe equation:

c = f where c = velocity of propagation in ms-1 (3 x 108 ms-1)

f = Frequency in Hertz (Hz) = Wavelength in meters (m)


9/50




1 - 1 - 9


Exercise

Exercise - Wavelenght

Calculate the wavelength of a 10 GHz signal.


10/50




1 - 1 - 10

Blank Page



11/50




1 - 1 - 11

2 Polarization


12/50




1 - 1 - 12

E

H

EARTH

Vertical Polarization

H

E

EARTH

Horizontal Polarization

2 Polarization

Polarization

The plane of polarization is defined in terms of the orientation of the E field with respect to the earth. Verticalpolarization and horizontal polarization are common forms of plane polarization.


13/50




1 - 1 - 13

2 Polarization

Exercise

In the vertical polarization is:

field E vertical to the ground?

field M vertical to the ground?


14/50




1 - 1 - 14

Blank Page



15/50


16/50




1 - 1 - 16

100 103 106 109 1012 10 15 10 18

Radio Systems Infra-red Ultra-violet

X-rays

Visible

Light

300 000km 300km 300m 0.3m 300pm300m 0.3 m

c = f x

Where c = 3 x 108 ms

3 Electromagnetic spectrum

Electromagnetic spectrum

The Figure illustrates the electromagnetic spectrum and indicates the portion occupied by radio systems.

Radio systems are identified by their frequency or wavelength of operation.

The Figure shows the relationship between frequency and wavelength(Example: f = 10 GHz =3 cm.)


17/50




1 - 1 - 17

4 Radio spectrum


18/50




1 - 1 - 18

Band Frequency Typical UseVLF up to 30 kHz Navigation systems

LF 30 300 kHz Long-range broadcast, navigation systems

MF 300 3000 kHz Medium wave broadcast and communications

HF 3 30 MHz Long-range commercial and military communications

VHF 30 300 MHz Mobile communications

UHF 300 3000 MHz Mobile communications

SHF 3 30 GHz Point-to-point microwave links, including satellitecommunications

EHF >30 GHz Point-to-point microwave links (Experimental systems)

4 Radio spectrum

Radio spectrum

The radio spectrum is sub-divided into a number of bands. The Figure lists these bands and the typical use ofeach band.

Factors influencing the use of a particular frequency band for a given application include:

Propagation mechanism - choice of Surface, Sky or Space wave depending on desired range.

Antenna size - consideration of particular antenna construction for given applications.

Capacity - ability of a small carrier deviation to deliver the required bandwidth and hence bit rate.


19/50




1 - 1 - 19

5 Use of the spectrum


20/50


21/50




1 - 1 - 21

Radio frequency channel arrangements for radio-relay systems in frequency bands

above about 17 GHz

Band

(GHz)

Frequency range

(GHz)

Rec. ITU-R

F-Series

Channel spacing

(MHz)18 17.7 19.7

17.7 21.217.7 19.717.7 19.717.7 19.7

595

595, Annex 1595, Annex 2595, Annex 3595, Annex 4

220; 110; 55: 27.5

160220; 80; 40; 20; 10; 6

3.513.75; 27.5

23 21.2 23.621.2 23.621.2 23.621.2 23.621.2 23.621.2 23.622.0 23.6

637637, Annex 1637, Annex 2637, Annex 3637, Annex 4637, Annex 5637, Annex 1

3.5; 2.5 (patterns)112 to 3.5

28; 3.528; 14; 7; 3.5

50112 to 3.5112 to 3.5

27 24.25 25.2524.25 25.2525.25 27.5

25.25 27.527.5 29.5

27.5 29.527.5 29.5

748748, Annex 3

748

748, Annex 1748

748, Annex 2748, Annex 3

3.5; 2.5 (patterns)56; 28

3.5; 2.5 (patterns)

112 to 3.53.5; 2.5 (patterns)

112 to 3.5112; 56; 28

31 31.0 31.3 746, Annex 7 25; 50

38 36.0 40.536.0 37.0

749749, Annex 3

3.5; 2.5 (patterns)112 to 3.5

55 54.25 58.2

54.25 57.257.2 58.2

1100

1100, Annex 11100, Annex 2

3.5; 2.5 (patterns)

140; 56; 28; 14100

5 Use of the spectrum

Use of the spectrum


22/50




1 - 1 - 22

Blank Page



23/50




1 - 1 - 23

6 General characteristics on the ITU-R recommendedfrequency plans


24/50




1 - 1 - 24

6 General characteristics on the ITU-R recommended frequency plans

General characteristics on the ITU-R recommended frequency plans [cont.]

Separate sub-bands for Tx and Rx channels, with a central guardband.

Constant channel spacing between co-polarized channels.

Two types of channel arrangements: InterleavedCo-Channel

Criteria followed by ITU- R:

Below 12 GHz: Compatibility of channel arrangements in the transitionfrom Analog to Digital systems.

Above 12 GHz: Channel arrangements optimized for Digital systems.


25/50




1 - 1 - 25

INTERLEAVED CHANNEL ARRANGEMENT

...

z

x

1

Pol.

H(V)

V(H)

2

3

4 y

1

2

3

4 N

...

z

F

GO CHANNELS RETURN CHANNELS

N-1 N-1

x/2 x/2

N


General characteristics on the ITU-R recommended frequency plans [cont.]

x = Co-polar channel spacing

y = Central guard band

z = Edge guard band


26/50




1 - 1 - 26

CO-CHANNEL ARRANGEMENT

...1

Pol.

H(V)

V(H)

2

3

4

y

1

2

3

4 N

...

z

F

GO CHANNELS RETURN CHANNELS

z x

N


General characteristics on the ITU-R recommended frequency plans

x = Co-polar channel spacing

y = Central guard band

z = Edge guard band


27/50




1 - 1 - 27

7 Antenna System


28/50




1 - 1 - 28

RX

Antenna Gain

IdealIsotropicRadiator

TheoreticalHalf-Wave

Dipole PraticalAntenna

Main Lobe

2.15 dBi

Antenna Gain dBi

Boresight

PracticalAntenna

Side Lobes

0 dBi

7 Antenna System

Antenna System [cont.]

Isotropic radiator

An isotropic radiator radiates the energy evenly in all directions. Its radiation diagram is thus circular in bothvertical and horizontal planes. Though a truly isotropic source is unrealizable it is easy to describe mathematicallyand is a useful reference.

Antenna gain

Antenna gain is the result of the focusing action of a practical antenna, radiating more energy in one directionand less in others. The axis along which maximum energy or field strength is radiated is termed the boresight andmay be readily identified from a polar diagram of field strength in a given plane (see the next figure).

The antenna gain is the ratio of the field strength along the boresight compared to that which be produced by anisotropic radiator radiating the same total power.

Gain = 10 log (F antenna /F iso) dBiNote: dBi means the use of the isotropic antenna as reference

The dipole is only loosely directional perpendicular to the plane containing its axis and, due to symmetry, notdirectional in the other plane (this property is called omni-directional).

The dipole is also easy to analyze mathematically. Its gain compared to an isotropic source is 2.15 dBi.

EIRP (Effective Isotropic Radiated Power)

EIRP of an antenna is:

Input power to the transmission line feed feeder losses + antenna gain in dBi


29/50




1 - 1 - 29

Beamwidth

Antenna lobe(Main)

Max. gain-3 dB

Boresight(Max. gain)

Max. gain-3 dB

Antenna

Beam widthto half

Power point 3dB

7 Antenna System


Antenna beamwidth

Antenna beamwidth is the angular distance between the half power (-3 dB points) on the polar diagram (see thenext Figure).

Though this is the angle normally used to asses what an antenna will see, radiation and reception does occuroutside of the beamwidth in the mean beam and in the sidelobes, when present as this a potential source ofinterference.

Antenna bandwidth

Most antennas are designed at some center frequency. As the operating frequency is moved away from this thedimensions of the antenna in terms of wavelength will vary and will be consequential changes in radiation pattern(gain and beamwidth), antenna impedance and hence VSWR in the antenna feed, etc. Any of this parameterscould be a practical limit on the range of frequencies used for a given antenna.

Front to Back ratio

The Front to Back ratio is a measure of how well the antenna discriminates from a signal entering along theboresight compared to the reverse direction and is a factor in reducing interference

Cross-Polar Discrimination

Antennas (or their feed arrangements) are designed to operate in one plane of polarization. This is useful forfrequency re-use as it is possible to have two links operating at the same frequency, but with differentpolarization. To prevent mutual interference between the two systems their antennas should not receive theincorrect polarization.

Cross-polar discrimination is the measure of how successful this is and the ratio of the wanted to unwantedsignals received in dB.


30/50


31/50




1 - 1 - 31

HHVV

VH

HV

7 Antenna System


Parallel and cross-polar response are represented for both horizontal an vertical polarizations. The curves areidentified as follows:

HH - Response of a horizontally polarized port to a horizontally polarized signal

HV- Response of a horizontally polarized port to a vertically polarized signal

VV- Response of a vertically polarized port to a vertically polarized signal

VH - Response of a vertically polarized port to a horizontally polarized signal


32/50




1 - 1 - 32

A

Antenna

X

Parabolic antenna

B

X

Z

Wavefront

The Parabolic antenna surface focuses thearriving plane on the antenna.

ie RAX = RBX

7 Antenna System


Parabolic antenna

This antenna consists of a large reflecting surface (geometry is parabolic), this creates a focal point from whichenergy can be fed to illuminate the dish: when receiving signals the parabolic dish concentrates the energy ontothe focal point.

The next figure illustrates the importance of the antenna geometry, energy illuminating the reflector from the focalpoint will create a parallel wavefront in front of the dish.

The parabolic antenna is highly directional with a gain typically of 40-50 dBi. The gain is related to thedimensions of the reflector relative to the signal wavelength.

The antenna concentrates most radiation into the main lobe, which typically has a 3 dB beamwidth of a fewdegrees.

The antenna does produce a number of undesired side lobes which are in the order of 25 dB down on the mainlobe.


33/50




1 - 1 - 33

Antenna gain

The gain of a parabolic antenna is:

where: D = antenna diameter (m)

= signal wavelength (m) = antenna efficiency (usually is from 0.55 to 0.65)The efficiency is related to the irregularities in the antenna and illumination.

Another approximation of gain is:

G (dBi) = 20 log F + 20 log D + 18.2 + 0.5 (depending on )

where: F = signal frequency (GHz)

D = antenna diameter (m)

2

=

DG

7 Antenna System



34/50




1 - 1 - 34

Antenna beamwidth

The 3 dB beamwidth of a parabolic antenna is:

where: = wavelength (m)D = antenna diameter (m)

degrees)(D

70dB)(3Beamwidth =

7 Antenna System



35/50




1 - 1 - 35

(a) Parabolic Dish (b) Offset Horn

Typical Microwave Antennas

7 Antenna System


Feeder

The parabolic antenna can be fed in different ways, as shown in the Figure.

Center fed antennas can cause blocking of the aperture and reduced efficiency. This may be overcome byoffsetting the feed, but the feed point needs rigid support and such antennas, although more efficient, are bulkier.

A single feed point may be orientated to produce the desired polarization.

Twin feeds may be used to produce a dual polarization from a single dish.

Note: With circular waveguide it is possible to have V and H polarization in same feeder.

With elliptical waveguide it is possible only one polarization (Elliptical cross section is reallyrectangular).


36/50




1 - 1 - 36

a) f/D ratio

Focal PointD

Overspill Radiation

f

b) Antenna Shrouds

Antenna

Shroud

c) Tapered Illumination

ParabolicReflector

Illumination Intensity

Controlling Front-to-back Ratio

7 Antenna System

Antenna System

Front to Back ratio

The parabolic antenna has a relatively high front to back ratio (30 to 40 dB approx.). However some energy fromthe focal point feed overspills the reflector (as shown in Figure a). With diffraction effects the overspill can producesignificant radiation at the rear side of the antenna.

This is especially true of antennas with a small aperture diameter (D) compared to focal length (f), i.e. a large f/Dratio.

Decreasing f/D ratio by making the dish deeper reduces spillover, but degrades the radiation pattern, as theillumination is more uneven. The antenna is also larger and heavier.

If front-to-back ratio is critical, another option is to use a conducting shroud (as shown in Figure b) attached tothe front of the antenna to eliminate the overspill, but this again may have an adverse effect on the gain andradiation pattern.

Very often shrouds can be confused with antenna radomes.A radome offers physical protection to the antenna from the effects of the environment and is made from materialtransparent to microwaves.

An alternative techniques is to concentrate the illumination of energy at the center of the reflector and decreasethe illumination at the periphery. This tapered illumination is shown in Figure c. Amplitude tapering reduces thegain and increase the beamwidth, as the full aperture is not being fully used.


37/50


38/50




1 - 1 - 38

Blank Page



39/50




1 - 1 - 39

8 Field strength and related parameters


40/50


41/50


ISOTROPIC RECEIVER

The ability of a receiving antenna to receive power from an incident power flux is determined by its apparent oreffective aperture, (Ae) in m2. This is a function of the antennas construction and for an isotropic antenna isgiven by:

where = wavelength in meters

Power Received

Power received may be expressed by:

Free-space Propagation Loss

Free-space Propagation loss may be expressed as:

( )2m2

4

Ae = (Watts)4xd4PtPr 22=22

fsl

c

fd4

d4

Pr

PtA

=

==



1 - 1 - 41

4

x

d4

PAx

d4

PP

2

2

t

e2

t

r==

IsotropicRadiator

EffectiveAperture

in m2

Pt

Pr

d

Isotropic Receiver

Ae

8 Field strength and related parameters

Field strength and related parameters


42/50




1 - 1 - 42

Blank Page



43/50




1 - 1 - 43

9 Free space loss


44/50




1 - 1 - 44

The free space loss, expressed in dB, is a function of distance and frequency.

The free space loss equation may then be expressed as:

i.e. A fsl (dB) = 92.4 + 20 log F (GHz) + 20 log d (km)

where F = frequency in GHz

d = distance in km

( )2

8

93

fsl10x3

10x(GHz)Fx10x(km)d4log10dBA

=

9 Free space loss

Free space loss


45/50




1 - 1 - 45

9 Free space loss

Exercise

Exercise - Free-space loss attenuation

Calculate the free-space loss attenuation of a50 km link operating at 8 GHz.


46/50




1 - 1 - 46

Blank Page



47/50




1 - 1 - 47

10 Radio Network Design procedure


48/50




1 - 1 - 48


Radio Network Design procedure

Step 1: By starting with the simplest (low cost) configuration (1+0),calculate the PRx nom level by using the Power link budget

formula (Section 1, Module 2, Chapter 1) Step 2: Calculate the clearance of the hop (Section 1, Module 2,

Chapter 2 & 3)

Step 3: Calculate the PRx threshold (Section 1, Module 2, Chapter 4)

Step 4: Calculate the FM=PRx nom PRx threshold Step 5: By using the FM of Step 4 calculate the outage probability

due to the rain (Section 1, Module 2, Chapter 5)

Step 6: Calculate the outage probability due to the fading (Section 1,

Module 2, Chapter 6) Step 7: Calculate the objectives according to the ITU-T and ITU-R

reccomandations (Section 1, Module 2, Chapter 7)


49/50




1 - 1 - 49


Radio Network Design procedure

Step 8: If the outages of the link (calculated in Chapter 5 & 6) meetthe objective, go to Step 10

Step 9: Change the PRx nom level or use the Fadingcountermeasures (Section 1, Module 2, Chapter 8) in orderto meet the objective

Step 10: Consider all the possible interferences (Section 1, Module2, Chapter 9, 10 & 11) and calculate the new FM

Step 11: If, with the new FM, the objectives are always met, the radioplanning procedure is over. Otherwise go back to Step 9.


50/50



1 - 1 - 50

End of Module

transmission planning mod 1

Documents