Radio Network Planning

Section 1 - Module 1 - 3FL 42104 AAAA WBZZA Edition 2 - July 2005

All rights reserved © 2006, Alcatel- RADIO NETWORK PLANNING

1.1 Introduction to Network Planning3FL 42104 AAAA WBZZA Edition 3 - July 2006

Network Planning


Network Planning - Introduction to Network Planning


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Objectives

To be able to describe concepts such as:• Polarization • Frequency plans• Antenna parameters • Free space loss




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Table of Contents

Switch to notes view! Page

1 Electromagnetic waves 7Electromagnetic waves 8Exercise 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 plans 23General 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 47Radio Network Design procedure 48Radio Network Design procedure 49End of Module 50




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Table of Contents [cont.]





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1 Electromagnetic waves




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TEM Wave


Electromagnetic waves

f = 1/Tc = fλ

Electromagnetic WavesAn 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 are perpendicular to each other and to the direction of propagation and are hence referred to as TransverseElectro-Magnetic (TEM) waves.

Frequency, Wavelength and VelocityWavelength is the distance in meters between any two “similar” points on the wave. This portion of the wave is referred to as one complete cycle.Wavelength is given symbol “λ”.Frequency “f” 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 the velocity of 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 “λ” (wavelength) of an EM wave is given by the equation:

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

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




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Exercise

Exercise - Wavelenght

Calculate the wavelength of a 10 GHz signal.




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2 Polarization




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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. Vertical polarization and horizontal polarization are common forms of plane polarization.




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2 Polarization

Exercise

In the vertical polarization is:field E vertical to the ground?field M vertical to the ground?




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3 Electromagnetic spectrum




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100 103 106 109 1012 10 15 10 18

Radio Systems Infra-red Ultra-violet

X-rays

VisibleLight

300 000km 300km 300m 0.3m 300pm300μm 0.3 μm

c = f x λ

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 → λ=3 cm.)




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4 Radio spectrum




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Band Frequency Typical UseVLF up to 30 kHz Navigation systemsLF 30 – 300 kHz Long-range broadcast, navigation systemsMF 300 – 3000 kHz Medium wave broadcast and communicationsHF 3 – 30 MHz Long-range commercial and military communicationsVHF 30 – 300 MHz Mobile communicationsUHF 300 – 3000 MHz Mobile communications

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

EHF >30 GHz Point-to-point microwave links (and other applications)

4 Radio spectrum

Radio spectrum - nomenclature

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




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4 Radio spectrum

Radio spectrum - letter designation for MW bands

56.0 - 100-W

46.0 – 56.0a, b, c, d, eV

36.00 – 46.0a, b, c, d, eQ

10.90 – 36.00p, s, e, c, u, t, q, r, m, n, l, aK

5.20 – 10.90a, q, y, d, b, r, c, l, s, x, f, kX

1.550 – 5.20e, f, t, c, q, y, g, s, a, w, h, z, dS

0.390 – 1.550p, c, l, y, t, s, x, k, f, zL

0.225 – 0.390-P

f (GHz)Sub-bandBand

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




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5 Use of the spectrum




1 - 1 - 21Radio frequency channel arrangements for radio-relay systems in frequency bands below about 17 GHz

Band

(GHz)

Frequency range

(GHz)

Rec. ITU-R

F-Series

Channel spacing

(MHz)

Band

(GHz)

Frequency range

(GHz)

Rec. ITU-R

F-Series

Channel spacing

(MHz)1.4 1.35 – 1.53 Rec. [Doc. 9/12] 0.25; 0.5; 1; 2; 3.5 8 8.2 – 8.5

7.725 – 8.2757.725 – 8.2758.275 – 8.5

386386, Annex 1386, Annex 2386, Annex 3

11.66229.6540.7414; 7

2 1.427 – 2.691.7 – 2.1; 1.9 – 2.3

1.7 – 2.3

701382283

0.5 (pattern)2914

10 10.3 – 10.6810.5 – 10.6810.55 – 10.68


20; 5; 27; 3.5 (patterns)

5; 2.5; 1.25 (pattern)1.9 – 2.31.9 – 2.31.9 – 2.32.3 – 2.5

10981098, Annexes 1 and 2

1098, Annex 3746, Annex 1

3.5; 2.5 (patterns)1410

1; 2; 4; 14; 28

11 10.7 – 11.710.7 – 11.710.7 – 11.710.7 – 11.7

387, Annex 1 and 2387, Annex 3387, Annex 4387, Annex 5

40676080

2.29 – 2.26

2.5 – 2.7

Rec. [Doc. 9/13]

283

0.25; 0.5; 1; 1.75; 2; 3.5;7; 14; 2.5 (pattern)

14

12 11.7 - 12.512.2 – 12.7

746, Annex 4, § 3746, Annex 4, § 2

19.1820 (pattern)

4 3.8 – 4.23.6 – 4.23.6 – 4.2

382635

635, Annex 1

2910 (pattern)

90; 80; 60; 40

13 12.75 – 13.2512.75 – 13.2512.7 – 13.25

497497, Annex 1

746, Annex 4, § 1

28; 7; 3.535

25; 12.55 4.4 – 5.0

4.4 – 5.04.4 – 5.0

4.54 – 4.9

746, Annex 21099

1099, Annex 11099, Annex 2

2810 (pattern)40; 60; 80

40; 20

14 14.25 – 14.514.25 – 14.5

746, Annex 5746, Annex 6

28; 14; 7; 3.520

6L 5.925 – 6.4255.85 – 6.425

383383, Annex 1

29.6590; 80; 60

15 14.4 – 15.3514.5 – 15.3514.5 – 15.35

636636, Annex 1636, Annex 2

28; 14; 7; 3.52.5 (pattern)

2.56U 6.425 – 7.11

6.425 – 7.11384

384, Annex 140; 20

807 7.425 – 7.725

7.425 – 7.7257.435 – 7.757.11 – 7.75


728528


Use of the spectrum [cont.]




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

595595, Annex 1595, Annex 2595, Annex 3595, Annex 4

220; 110; 55: 27.5160

220; 80; 40; 20; 10; 63.5

13.75; 27.523 21.2 – 23.6

21.2 – 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 – 27.525.25 – 27.527.5 – 29.527.5 – 29.527.5 – 29.5

748748, Annex 3

748748, Annex 1

748748, Annex 2748, Annex 3

3.5; 2.5 (patterns)56; 28

3.5; 2.5 (patterns)112 to 3.5

3.5; 2.5 (patterns)112 to 3.5112; 56; 28

31 31.0 – 31.3 746, Annex 7 25; 5038 36.0 – 40.5

36.0 – 37.0749

749, Annex 33.5; 2.5 (patterns)

112 to 3.555 54.25 – 58.2

54.25 – 57.257.2 – 58.2

11001100, Annex 11100, Annex 2

3.5; 2.5 (patterns)140; 56; 28; 14

100


Use of the spectrum




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6 General characteristics on the ITU-R recommended frequency plans




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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 guard band.

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 transition from Analog to Digital systems.

Above 12 GHz: Channel arrangements optimized for Digital systems.




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INTERLEAVED CHANNEL ARRANGEMENT

...

z

x

1

Pol.

H(V)

V(H)

2

3

4y

1’

2’

3’

4’ N’

...

z

F

GO CHANNELS RETURN CHANNELS

N-1 N-1’

x/2 x/2

N

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

x = Co-polar channel spacingy = Central guard bandz = Edge guard band




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CO-CHANNEL ARRANGEMENT

...1

Pol.

H(V)

V(H)

2

3

4

y

1’

2’

3’

4’ N’

...z

F

GO CHANNELS RETURN CHANNELSz x

N

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

x = Co-polar channel spacingy = Central guard bandz = Edge guard band




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7 Antenna System




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RX

Antenna Gain

IdealIsotropicRadiator Theoretical

Half-WaveDipole

PraticalAntenna

Main Lobe

2.15 dBi

Antenna Gain dBi

Boresight

PracticalAntenna

Side Lobes

0 dBi

7 Antenna System

Antenna System [cont.]

Isotropic radiatorAn isotropic radiator radiates the energy evenly in all directions. Its radiation diagram is thus circular in both vertical and horizontal planes. Though a truly isotropic source is unrealizable it is easy to describe mathematically and is a useful reference.

Antenna gainAntenna gain is the result of the focusing action of a practical antenna, radiating more energy in one direction and less in others. The axis along which maximum energy or field strength is radiated is termed the boresight and may 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 an isotropic radiator radiating the same total power.Gain = 10 log (F antenna /F iso) dBiNote: dBi means the use of the isotropic antenna as referenceThe dipole is only loosely directional perpendicular to the plane containing its axis and, due to symmetry, not directional 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




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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 beamwidthAntenna beamwidth is the angular distance between the half power (-3 dB points) on the polar diagram (see the next Figure).Though this is the angle normally used to asses what an antenna will “see”, radiation and reception does occur outside of the beamwidth in the mean beam and in the sidelobes, when present as this a potential source of interference.

Antenna bandwidthMost antennas are designed at some center frequency. As the operating frequency is moved away from this the dimensions 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 parameters could be a practical limit on the range of frequencies used for a given antenna.

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

Cross-Polar DiscriminationAntennas (or their feed arrangements) are designed to operate in one plane of polarization. This is useful for frequency re-use as it is possible to have two links operating at the same frequency, but with different polarization. To prevent mutual interference between the two systems their antennas should not receive the incorrect polarization.Cross-polar discrimination is the measure of how successful this is and the ratio of the wanted to unwanted signals received in dB.




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3

1

2

3

2

1

1

23

123

7 Antenna System


Examples of Radiation Patterns

Radiation Patterns determine an antenna’s ability to perform under conditions of radio congestion and also limit the route capacity. Radiation patterns are dependent on antenna series and size. An RPE comparison of various antenna series is illustrated below.




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HHVV

VHHV

7 Antenna System


Radiation patterns of adual pol. Antenna

Measured versus Guaranted Pattern

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

HH - Response of a horizontally polarized port to a horizontally polarized signalHV - Response of a horizontally polarized port to a vertically polarized signalVV - Response of a vertically polarized port to a vertically polarized signalVH - Response of a vertically polarized port to a horizontally polarized signal




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A

Antenna

X

Parabolic antenna

B

XZ

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 which energy can be fed to illuminate the dish: when receiving signals the parabolic dish concentrates the energy onto the focal point.

The next figure illustrates the importance of the antenna geometry, energy illuminating the reflector from the focal point 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 the dimensions 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 few degrees.The antenna does produce a number of undesired side lobes which are in the order of 25 dB down on the main lobe.




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Antenna gain

The gain of a parabolic antenna is:

where: D = antenna diameter (m)λ = signal wavelength (m)η = 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 η)

where: F = signal frequency (GHz)D = antenna diameter (m)

2

⎟⎠⎞

⎜⎝⎛=

λπη DG

7 Antenna System


The parabolic antenna gain can be mathematically calculated starting from a flat wavefront of area A, where all the transmitted power is uniformly distributed as:

G = A (4π/λ2)

Because in the reality the power distribution can’t be uniform, we can take account of this by introducing the efficient area

Aeff = η A

Then the gain can be written G = η A (4π/λ2) = η (π D2/4) (4π/λ2) = η (π D/λ)2 (as in the main slide)

It is important to use this relationship reversely to derive the efficient area Aeff of a generic antenna (parabolic or any other shape) as:

Aeff = G (λ2/4π)

Because by definition the gain of an isotropic radiator is 1 , it is possible now to derive its efficient area as:

Aei = λ2/4π

(this will be necessary for the definition of free space attenuation)




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Antenna beamwidth

The 3 dB beamwidth of a parabolic antenna is:

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

degrees)(D

70λdB)(3Beamwidth =

7 Antenna System


May be interesting to consider that in the hypothesis that radiation is constant value inside a certain angle a and zero outside, by definition of gain we can write:

G = 4π/α2

Where 4π is the isotropic (full sphere) radiation angle and α2 is the solid angle representing the radiation of the antenna.With these assumptions we can derive the radiation lobe angular size (in radiants) as:

α = SQRT [4π/G] = SQRT [4πλ2 / η (π2 D2)] = λ/ π D x SQRT (4π /η ) ≅ 50 λ / D

But the formula in the main slide is empirically corrected and takes into account of the typical shape of the main radiation lobe.




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(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 by offsetting 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).




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a) f/D ratio

Focal PointD

Overspill Radiation

f

b) Antenna Shrouds

Antenna

Shroud

c) Tapered Illumination

ParabolicReflector

Illumination IntensityControlling Front-to-back Ratio

7 Antenna System

Antenna System

Front to Back ratioThe parabolic antenna has a relatively high front to back ratio (typically more than 50 dB). However some energy from the focal point feed overspills the reflector (as shown in Figure a). With diffraction effects the overspill can produce significant 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/D ratio.Decreasing f/D ratio by making the dish deeper reduces spillover, but degrades the radiation pattern, as the illumination 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 to the front of the antenna to eliminate the overspill, but this again may have an adverse effect on the gain and radiation 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 material transparent to microwaves.An alternative techniques is to concentrate the illumination of energy at the center of the reflector and decrease the illumination at the periphery. This tapered illumination is shown in Figure c. Amplitude tapering reduces the efficiency and increase the beamwidth, as the full aperture is not being fully used.




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7 Antenna System

Exercise

Exercise 1 - Front to back ratio What is the front to back ratio in a parabolic antenna? Exercise 2 - Antenna gain

Calculate the gain of a 1 m parabolic antenna at 6 GHz. Exercise 3 - Antenna gain

Calculate the gain of a 1 m parabolic antenna at 24 GHz. Exercise 4 - Antenna beamwidth

Calculate the 3 dB beamwidth of a 2 m parabolic antenna at 10 GHz.




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8 Field strength and related parameters


A model which can be used to approximate the propagation loss between two points is the Free Space model. As its name implies here should be no significant obstructions or surfaces adjacent to the path. It also assumes isotropic characteristics at the transmitter and receiver and that propagation is through a vacuum.

Isotropic Radiation

If a transmit power, Pt (Watts), is fed into an isotropic source, then the power will radiate evenly in all directions causing an even Power Flux, Fiso, measured in Wm-2.As the power is evenly distributed over the surface of an expanding sphere the power flux is given by:

where Pt = Power transmitted in Wattsd = range of measurement in metres

as shown in next Figure power Flux thus falls according to the square of distance - the inverse square law.



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IsotropicRadiator

PowerFlux

per squaremeter

at distance d

Pt

1m

1m

d

Isotropic Radiator

2iso d4πPtF =


Field strength and related parameters [cont.]

( )224

−= Wmd

PtFiso π


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

where λ = wavelength in meters

Power ReceivedPower received may be expressed by:

Free-space Propagation LossFree-space Propagation loss may be expressed as:

(Watts)π4λx

dπ4PtPr

2

2=

22

fsl cfdπ4

λdπ4

PrPtA ⎟

⎠⎞

⎜⎝⎛=⎟

⎠⎞

⎜⎝⎛==



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π4λx

dπ4PAx

dπ4PP

2

2t

e2t

r ==

IsotropicRadiator

EffectiveAperture

in m2

Pt

Pr

d

Isotropic Receiver

Ae


Field strength and related parameters

by remembering that effective area of the isotropic

radiator isAei = λ2 / 4π




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9 Free space loss




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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. Afsl (dB) = 92.4 + 20 log F (GHz) + 20 log d (km)

where F = frequency in GHzd = distance in km

( )2

8

93

fsl 10x310x(GHz)Fx10x(km)dπ4log10dBA ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

9 Free space loss

Free space loss




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9 Free space loss

Exercise

Exercise - Free-space loss attenuation

Calculate the free-space loss attenuation of a 50 km link operating at 8 GHz.




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10 Radio Network Design procedure




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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 budgetformula (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 probabilitydue 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-Rreccomandations (Section 1, Module 2, Chapter 7)




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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.




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End of Module

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


1.2 Network Planning Method3FL 42104 AAAA WBZZA Edition 3 - July 2006

Network Planning


Network Planning - Network Planning Method


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Objectives

“Power budget”: to be able to calculate the power budget of a radio hop. “Effects of atmosphere”: to be able to understand the effects of the atmosphere on a radio hop, to calculate the attenuation introduced by the atmosphere gases.“Diffraction”: to be able to calculate the Fresnel zone radius and to satisfy the clearance rules.“Equipment parameters related to propagation”: to be able to understand the modulation concepts and to calculate the Rx powerthreshold.“Propagation during rain”: to be able to calculate the rain unavailability. “Propagation model”: to be able to calculate the outage due to a flat fading and to a selective fading.




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Objectives

“Quality objectives of Digital Radio Links”: to be able to calculate the objectives set by the Recommendations.“Fading countermeasures”: to be able to calculate the improvement due to the diversity configurations.“Reflections from ground”: to be able to understand the problems due to the reflections from ground.“Frequency re-use”: to be able to understand the frequency re-use configuration.“Interferences”: to be able to calculate the degradation introduced by the interference signals.




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Table of Contents


1 Power budget 7L.O.S. (Line Of Sight) Radio Links 8Main Propagation Phenomema 9Radio Link Equation 11Free Space Loss 12Antenna Gain 13Losses 15Exercise 16Exercise 17Blank Page 18

2 Effects of atmosphere 19Fixed terrestrial microwave link propagation 20Refraction through the atmosphere 24Anomalous propagation 29Exercise 30K-factor 32Variability of the K-factor 35Attenuation by atmosphere gases 37Exercise 38

3 Diffraction 39Diffraction 41Exercise 42Fresnel zones 43First Fresnel zone radius 45Exercise 46Obstruction loss 47Clearance rules 48

4 Equipment parameters related to propagation 49PRx Threshold General Formula 54Exercise 55Exercise 56Signature measurement 59Blank Page 60

5 Propagation during rain 61Propagation during rain 63Attenuation by rain 69Rain Unavailability Prediction 70

6 Propagation model 71Fade margin 73Fading definitions 74Exercise 75Flat fading outage 78Exercise 79Selective fading outage 84Exercise 85Single channel global outage 86

7 Quality objectives of Digital Radio Links 87Introduction 88ITU-T recommendations 89Error Performance Events 90Impact of propagation on performance objectives 91ITU-T G.821 100Rec. ITU-T G.826 and G.828 110Rec. ITU-T G.826 and G.828 - ITU-R F.1092 112Rec. ITU-T G.826 and G.828 - ITU-R F.1397 117




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Rec. ITU-T G.826 and G.828 - ITU-R F.1189 119Rec. ITU-T G.826 and G.828 - ITU-R F.1491 121Exercise 122

8 Fading countermeasures 123Adopted techniques 124Diversity Improvement 131Frequency diversity 132Exercise 133Space diversity 134Exercise 135Space and frequency diversity 137Angle diversity 138

9 Reflections from ground 139Reflections from ground 140Geometrical model 141Rx signal with reflection 142Rx signal level 143Exercise 144Space diversity in reflection paths 145Exercise 146

10 Frequency re-use 147Introduction 149Terminology 150Exercise 151Concepts 152Interferences 153Interference types 154Frequency reuse system block diagram 155Same frequency re-used channel (cross-polar) 156Exercise 157Adjacent frequency re-used channel (co-polar) 158Prediction of outage due to multipath propagation 161Prediction of outage due to rain effects 164

11 Interferences 165Introduction 166Modem performances 167Local sources 169Signals belonging to the same system at a common location 171Signals belonging to the same system from other locations 172Signals belonging to the same system from other locations through an overreach condition 173Exercise 174Blank Page 175End of Module 176




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1 Power budget




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1 Power budget

L.O.S. (Line Of Sight) Radio Links

The electromagnetic wave propagation of L.O.S. RADIO systems is in the lower part of atmosphere, near the ground.

The presence of the atmosphere and of the ground can affect the RF propagation.

PROPAGATION depends on:• CLIMATIC CONDITIONS• RF FREQUENCY BAND• RADIO HOP LENGTH• GROUND CHARACTERISTICS

Propagation

Site A Site B




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1 Power budget

Main Propagation Phenomema

Atmosphere:Atmospheric AbsorptionRefraction through the atmosphere: Ray CurvatureRefraction through the atmosphere: Multipath Propagation.

Rain:Raindrop AbsorptionRaindrop ScatteringRF Signal Depolarization.

Ground:Diffraction through ObstaclesReflections.




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1 Power budget

Radio Link Equation [cont.]

GTx GRxAfsl

Aa

ABRTx

AfTx

PTx

ABRRx

AfRx

PRx




1 - 2 - 11

1 Power budget

Radio Link Equation

PRx = PTx + GTx + GRx - Afsl -Aa - Af,Rx - Af,Tx - ABR - A - M

PRx : received power [dBm]PTx : transmitted power [dBm]Afsl : propagation free-space loss [dB]Aa : atmospheric absorption loss [dB]GTx : transmit antenna gain [dB]GRx : receive antenna gain [dB]Af,Tx : loss in the transmit feeder [dB]Af,Rx : loss in the receive feeder [dB]ABR : loss in the RF branching (filters) system [dB]A : other attenuations (mirrors, back-to-back antennas, attenuators) [dB]M : Margin (tolerance) [dB]




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1 Power budget

Free Space Loss

Afsl is the propagation free-space loss and depends on the operating frequency “F” [GHz] and the hop length "L" [km]:

Afsl (dB) = 92.4 + 20 log (F) + 20 log (L) FSL increase 6 dB if:the hop length is doubledorthe frequency is doubled.

Att. [dB]

4110

120

130

140

150

Distance [km]8 12 16 20 24 28 32 36 40 44 48

2 GHz

4 GHz6 GHz7 GHz

10 GHz15 GHz




1 - 2 - 13

1 Power budget

Antenna Gain

Antenna gain depends on its diameter “D” [m] and on the operating frequency "F” [GHz]:

In dB units: (depending on η)

Antenna gain is 6 dB higher if:- antenna diameter is doubled,

for a given frequency- frequency is doubled, for a given

diameter.

2

⎟⎠⎞

⎜⎝⎛=λ

πη DG

5.02.18)log(20)log(20 ±++= FDG

AntennaGain [dB]

030

Frequency [GHz]5 10 15 20

34

38

42

46

50

0.5m

1m

2m3m

4m

65.055.0 −== efficiencyAntennaη




1 - 2 - 14

Feeder loss (Af)Feeder systems loss depends on its specific attenuation (dB/100m) and its length.

Branching loss (ABR)ABR is the branching system loss: it may be evaluated by the characteristics of the radio equipment.In this term it is necessary to insert the total branching loss depending on the system configuration (i.e. total number of RF circulators and point of measurements of Tx and Rx power).

Other losses (A)We may consider every kind of other losses like passive repeater systems, carried out by passive repeaters or back-to-back antennas, attenuators, radomes, obstructions, etc.

Margin (M)At the end, a value of tolerance may be added (normally 1 dB).

1 Power budget

Losses [cont.]




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1 Power budget

Losses

Waveguide Attenuation

EW = Elliptical WaveguideWC = Waveguide CircularWR = Waveguide Rectangular




1 - 2 - 16

In practice a terrestrial fixed link is not propagating through a vacuum, but rather the various gases that make up the Earth’s atmosphere.

At frequencies above 10 GHz the attenuation experienced by a radio wave is due to these gases.

Water vapour (H2O) and oxygen (O2) molecules in particular, interact with electromagnetic wave energy of specific frequencies to produce oscillation or molecular resonance within their structure.

This excitation of the molecules draws power from the electromagnetic wave causing strong attenuation, as shown in next Figure.

Some other gases exhibit the same property, but only have a low density in the atmosphere.

The loss in the Figure is expressed as a specific loss in dB/km and is measured under “clear sky” conditions (i.e. no rain or fog).

The overall attenuation on a link at a given frequency may be simply calculated from:

Specific Attenuation x Path Length (dB)

2 Effects of atmosphere

Attenuation by atmosphere gases (ITU-R P.676)




1 - 2 - 17


Attenuation by atmosphere gases (ITU-R P.676)




1 - 2 - 18


Exercise

Exercise 1 - Atmosphere gas attenuationCalculate the attenuation due to the atmosphere gases in a 20 km link at 20 GHz.




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1 Power budget

Exercise

Exercise 2 - Power budget Calculate the power budget of the following link

operating at 6 GHz (Margin = 1 dB).

2 m 36 km

Aa = negligible

ABRTx= 0.5 dB

(EW64)50 m

PTx = +30 dBm

2 m

(EW64)50 m

ABRRx= 0.5 dBPRx = ?




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1 Power budget

Exercise

Exercise 3 - Antenna gain calculationCalculate the gains of the antennas to be used inthe following link:

PTx : +30 dBmPRx : -36 dBmFrequency : 6 GHzDistance : 48 kmLosses of branching filters and feeder in station 1 : 1.5 dBLosses of branching filters and feeder in station 2 : 2.5 dB




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Blank Page





1 - 2 - 22





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Fixed terrestrial microwave link propagation

A fixed terrestrial microwave link propagate through the lower portion of the earths atmosphere, referred to as the troposphere.

The troposphere contains all the “weather” and parameters such as temperature, water vapour and atmospheric pressure change between different locations and with time. The problem is that at microwave frequencies the path an electromagnetic ray path takes depends greatly on the value of these parameters so as they vary so will the radio links path profile.

A need obviously exists to be able to quantify the make up to the atmosphere and to be able to predict its effect on the ray path.




1 - 2 - 24


Refraction through the atmosphere [cont.]

Under normal conditions (the so-called standard atmosphere)temperature, water vapour and atmosphere pressure will fall with height. The fall in these values also represents a fall in the refractive index (n) “seen” by the electromagnetic wave and Snell’s lawdictates that the ray will be bent away from the normal and backtowards the earth’s surface, a process referred to as refraction. Although refractive index normally falls continuously with height we could consider a layered structure shown in the next Figure.

For a standard atmosphere the resulting curvature is less than the earth’s.




1 - 2 - 25



Snell’s Law

where: c = velocity of light (vacuum)v = velocity of light (medium) →

The index of refraction (n) is the ratio of the velocity of light in a vacuum to the velocity of light through some medium.

n ranges from 1.0 to 1.00045 (typ. 1.0003)

Snell’s Law states that a ray passing from a medium of higher refractive index into (n1) a medium of lesser refractive index (n2) is bent away from the normal.

1122

21

cosαncosαnnn

×=×>

vcn =

με1v =

n

1 1n

22




1 - 2 - 26



Atmosphere layered structure

Earthn1

n2

n3

n4

n5

Etc.




1 - 2 - 27


Refraction through the atmosphere

As “n” differs only slightly from unity, it is usually convenient to work with the following quantity:

N is termed "refractivity" (Refer to Rac. ITU-R P.453-6 for the values of N in the world). (A refractivity of 350 N-units corresponds to a value 1.000350 of the index of refraction “n”).

where: P = atmospheric pressure (mb)T = temperature (°K)e = partial pressure of water vapor (mb)

In general the axis of a microwave beam lies within a hundred meters from ground.

It is known that at these elevations and in a well-mixed atmosphere the refractivity decreases uniformly with the height “h” and therefore its gradient

is constant with h.This does not mean that G remains constant in time.On the contrary it greatly varies with metereological conditions.The median value of G (temperate climate) is -40 N-units/Km

( ) 6101 ×−= nN

termwettermdryTe103.73

TP77.6N 2

5 +=⎟⎠⎞

⎜⎝⎛××+⎟

⎠⎞

⎜⎝⎛×=

dhdNG =




1 - 2 - 28


Anomalous propagation [cont.]

Standard Conditions

Standard Conditions

The standard atmosphere has a linear fall of around 40 N units per kilometer of height. This may be expressed as a dN/dh of -40 units/km.The daily and seasonal changes in the meteorological conditions produce changes in the refractivity of the atmosphere. A well designed microwave link will allow the link to operate for all but the most extreme of these changes.Broadly there are three abnormal conditions that will give tise to anomalous propagation.




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Sub-refraction

(a) N profile

h

N

Standard

Nnegativedh

positivedh

dh = 0

negative

positive

0

(b) Off boresight path profile and reduced clearance

NN

Standard

Sub-refractive Conditions

When the refractivity decreases more slowly than normal, or even increases with height, then the atmosphere is said to be sub-refractive. Under these conditions dN/dh is greater than -40 units/km (and K is less than 4/3). The N profile is shown in next Figure.Note that the ray path for mild sub-refractive conditions has different launch and arrival angles compared to standard refraction and this will cause a reduction in received signal level due to the reduced gain of the antennas off bore sight. Sub refraction tends to reduce path clearance as the reduced K makes the Earth bulge effectively larger, increasing the diffraction loss. If the sub-refraction is extreme then the terrain between the two sites will block the ray path causing obstruction fading.All of these effects will cause a loss in Received Signal Level (RSL) across the whole of the system’s bandwidth, i.e. flat fading.




1 - 2 - 30



(a) N profile

Super-refraction

Standard

Super -Standard

(b) path profile

Super-refractive Conditions

When the refractivity increases more rapidly than normal (dN/dh less than -40 units/km) the atmosphere is said to be super-refractive (and K will be greater than 4/3).The N profile is shown in next Figure.Note again that the ray moves off bore sight as the refractivity changes and that the ray path becomes closer to being parallel to the earth’s surface. The first effect will give rise to a loss of signal strength at the receiver, whilst the second could enable propagation over long distances which could give rise to interference problems.




1 - 2 - 31


Exercise

Why does not the electromagnetic wave travel in astraight line?

due to the gravity of the earthdue to the refractive gradient of the atmospheredue to the magnetic field of the earth

What does it mean standard atmosphere?




1 - 2 - 32


K-factor [cont.]

EQUIVALENT EARTH RADIUS AND FLAT EARTH

In ray tracing problems it is often convenient to use a geometrical transformation to produce diagrams where either straight rays propagate above an “equivalent earth” of effective radius KRo or alternatively, rays of effective radius KRo propagate above a “flat earth”.

In either case the value of K (called “effective earth radius factor”) is such that the ray elevation E(x) above the terrain has the same functional relationship to the distance x as in the original diagram.

where G is expressed in N - units/km

dhdNGwhereG10

dhdn

ρ1 6 =−=−= −

ρ1

R1

R1

oeq

−=

G10R1

ρ1

R1

KR1 6

ooo

−+=−=

Ro

G157157K1G10

R1KR 6

oo +

=⇒=⎟⎟⎠

⎞⎜⎜⎝

⎛+ −

⎟⎟⎠

⎞⎜⎜⎝

⎛=== −

•6

oooeq 10157

R1;km6370RKRR




1 - 2 - 33


K-factor

FLAT EARTH

B (x)

E (x)

x' d-x

T

h1

T'

R

h2

R'

RAY

KR0

EQUIVALENTEARTH

E (x)

x d-x

T

h

T'

R

h

R'

RAY

H (x)

B (x)

KR

E (x)

x d-x

T

h1

T'

R

h2

R'

RAY

H (x)

BE (x)

R0

BR (x)

REAL CASE

ρ




1 - 2 - 34


Variability of the K-factor [cont.]

The Vertical Refractivity Gradient G and the K-factor are time varying parameters, depending on daily and seasonal cycles and on meteorological conditions. Their range of variation is more or less wide, depending on the climatic region.

In cold and temperate regions the range is rather narrow, while in tropical regions it is very wide. Experimental observations show for example that the probability of K< 0.6 in temperate climates is generally well below 1%. In tropical climates the same probability may be in the range 5% - 10%.

This means that, in tropical regions, there is the highest probability of observing propagation anomalies due to extreme K-factor values.

In a well planned link, tower-heights are designed in such a way that visibility between terminals is still assured for the “lowest” ray to be expected on the path.

In practice such a minimum is taken as that value, say K (0.01%), which is not exceed for 0.01% of the time.

( )( )0.01%G157157K

emin +

=




1 - 2 - 35


Variability of the K-factor [cont.]

Figure shows K(0.01%) as a function of path length “d” for the three distributions of G given:

a temperate climate b northern climate c tropical climate

Considerable differences may be observed between the curves. As expected, however, all increase as the hop get longer.It is important to determine the minimum k-factor, because in this case the radio ray is closer to the ground (maximum obstruction probability).




1 - 2 - 36


Variability of the K-factor

0.2

1.4

1.2

1

0.8

0.6

0.4

10 20 40 60 80 100 200

a

b

c

PATH LENGTH, Km

K N

OT

EX

CE

ED

ED

FO

R 0

.01%

OF

TIM

E




1 - 2 - 37


Anomalous propagation

Causes of anomalous propagation (ducting)

The sensitivity of the refractivity of the earth’s atmosphere is such that changes of a few degrees in temperature and a few millibars in water vapour pressure, which can exist between adjacent masses in certain meteorological conditions, can lead to the refractivity changing by 10s of units over a height of a several 10s of metres. The resulting ducts, when they form, can trap radio energy giving rise to both “holes” in coverage and extended ranges.

Ducts may be caused by:

EvaporationA shallow surface based duct will normally exist over a sea or other large body of water. It is formed due to the rapid decrease of water vapour pressure in the first few metres above the water’s surface and its thickness depends on the geographic region varying from 5m over the North Sea to 20m in the Gulf.




1 - 2 - 38



Nocturnal RadiationThe Earth tends to loose its daytime heat quickly at night and under calm windless conditions can cause a temperature inversion. If there is a lot of water vapour present fog can occur, causing an increase in water vapour pressure with height and cause subrefraction. However if there is little water vapour, then the temperature inversion will cause super-refraction and even ducting. This form of duct disappears shortly after sunrise as the suns’heat breaks down the inversion layer.

Subsidence InversionUnder high pressure conditions large, dense and cool air masses are heated by compression as they descend, and so form a strong temperature inversion with respect to the cooler air nearer the surface, creating an elevated duct.

AdvectionIn coastal regions a relatively warm air flow across a cooler sea will cause a temperature inversion and form a surface based duct.

Weather FrontsCool dense air may force less dense warmer air above it, causing a temperature inversion and a raised duct.




1 - 2 - 39



Ducts For represent ducts we must introduce the parameter M = N + 157x h (With this parameter in a M versus heigth diagram, G= dN/dh = -157 is represented by a vertical line)

h

M

G < -157

G ~ standard

a) Ground based duct

h

M

G < -157

G ~ standard

a) Elevated duct

G ~ standard




1 - 2 - 40

3 Diffraction




1 - 2 - 41

3 Diffraction

Diffraction [cont.]

Diffraction is the bending of the electromagnetic waves around an obstacle depending on the wavelength and the obstacle itself according to Huygens' theory.

Every point belonging to a wave front has the property of generating secondary waves.

Wave front is the locus of points with the same phase.

Line-of-sight conditions is not necessary because reception is possible through high order waves.

The relevance of diffraction is that obstacles near the microwave beam can affect propagation introducing additional losses.

A B

a1

t0 t0 + dt

a2

a3

a4

a5

b1

b2

b3

b4

b5




1 - 2 - 42

3 Diffraction

Diffraction

Tx Rx

Activatedfictitioussources

Non-activatedfictitioussources




1 - 2 - 43

3 Diffraction

Fresnel zones

For each point in the plane the phase shifts between P and all the other sources depend ONLY on the path difference: the locus of points having a path difference between the two antennas = nλ/2 and phase shift of nπ is an ellipsoid with radius F1.

2....1,nwhere2λnTxRx PRxTxP =+=+

Tx RxD

a) Side View

b) Cross Section1st Fresnel (D + λ/2)

2nd Fresnel (D + λ)

3rd Fresnel (D + 3λ/2)

1st Fresnel (D + λ/2)

2nd Fresnel (D + λ)

3rd Fresnel (D + 3λ/2)

P

+

-

+




1 - 2 - 44

3 Diffraction

First Fresnel zone radius [cont.]

The first Fresnel Ellipsoid Radius at a distance D1 (km) from one hop terminal is:

F = Frequency (GHz) D = Hop length (km)

The equation shows that F1 depends both on the operating frequency (F) and the distance from terminals.

F1 is maximum for D1 = D/2.

( )( ) ( )m

DFDDDF 113001 −

=




1 - 2 - 45

First Fresnel Ellipsoid Radius at the middle of the path (D1=0.5D).

Fresnel Radius [m]

0 20 40 60 80 1000

10

20

30

40

50

60

D=Hop Length [km]

12 GHz

7 GHz4 GHz

2 GHz

3 Diffraction

First Fresnel zone radius




1 - 2 - 46

3 Diffraction

Exercise

Exercise 1 - First Fresnel ellipsoid radius Calculate the radius of the first Fresnel ellipsoid at

10 km distance from one hop terminal (Frequency: 7 GHz; Hop length: 40 km).




1 - 2 - 47

3 Diffraction

Exercise

Exercise 2 - Antenna heigthsCalculate the heights of the antennas in a 60 km link at 7 GHz. The path is flat with a 20 m knife-edge obstacle in the middle (clearance: 100%).

For the purpose of this exercise we can take, to simplify, the earth flat (it will be like to take G=-157).Otherwise we can put into account the “bulge” B of the earth at a certain distance X from one terminal of a link with length L, that is:

1B(X) =2KRo

X (L – X)




1 - 2 - 48

3 Diffraction

Obstruction loss

Diffractionloss relativeto free space (dB)

Normalized clearance h/F1

-1.5 -1 -0.5 0 0.5 140

30

20

10

0

-10

B

Ad D

Diffraction loss for obstructed line-of-sight microwave radio pathsB : theoretical knife-edge loss curveD : theoretical smooth spherical Earth loss curve at 6.5 GHz and k=4/3Ad : empirical diffraction loss for intermediate terrainh : amount by which the radio path clears the Earth’s surface (m)F1 : radius of the first Fresnel zone (m)




1 - 2 - 49

3 Diffraction

Clearance rules

The practical problem in microwave radio path engineering consists in choosing antenna towers in such a way that they are not higher than necessary to meet the following objectives:1. negligibly small probability than visibility is lost under “anomalous”

propagation conditions2. acceptable diffraction losses under “normal” propagation

conditions.

There are several criteria currently in use. For example, a popular rule recommends that:1. clearance be unity or greater at K = 4/32. clearance be 0.6 or greater at the minimum K related to the

climatic region and the path length considered




1 - 2 - 50

4 Equipment parameters related to propagation




1 - 2 - 51


PRx Threshold General Formula [cont.]

F =

Low Noise ErrorDetectorDemodulator

PRX(Th)

NF

RX

SN 10-6

=

PRX (Th)

N

F

10-3

PRX(Th)

NFSN 10-6

F = 1F > 1

TheoreticalPratical

NS input

NS outputEquipment parameters related to propagation




1 - 2 - 52



SN + 10 log F + 10 log N

10-6PRx (Th) =

K = Boltzman constantT =TemperatureB = Bandwidth

N = KTB

10 log N =10 log KT + 10 log B

if T = +25C°

10 log KT= - 114 dB

10 log N =10 log B - 114 dBDEPENDS ON THE

SN + 10 log F + 10 log B - 114 dB

10-6PRx (Th) =

RFAmplifier

ModulationType

ModulationType

In dB




1 - 2 - 53



Example 1: Calculation of PRX threshold using different modulation types

fb = 140 Mbit/sRF = 6 GHzT =+25°C

4 PSK +13.5 + 4 + 10 log 140 - 114 = -78.1 dBmPRx (Th) =2

(22 = 4)

18.7

16 QAM +20.5 + 4 + 10 log 140 - 114 = -74.1 dBmPRx (Th) =4

(24 = 16)

15.5

64 QAM +26.5 + 4 + 10 log 140 - 114 = -70.2 dBmPRx (Th) =6

(26 = 64)

13.3

10 log F = 4 dB

PRx (Th) = ?

ModulationType

4 PSK

16 QAM

64 QAM




1 - 2 - 54



Example 2: 10-3 receiver threshold calculation

Input data F (dB) 2.50

BIT RATE (Mbit/s) 155.52 MOD. (nQAM) 128 7 levels

REDUNDANCY 1.06 S/N MODEM (dB) 26.00

SYMB. RATE (MHz) 23.5

THRESHOLD (dBm) = KTB (symbol) + F + S/N modem

THRESHOLD -71.78 memo

KTB -100.53 KT (dB) -114

KTBF -98.03 THERMAL NOISE




1 - 2 - 55


PRx Threshold General Formula

FM = PRX(NOM) - PRX(Th)

FM = Fading Margin

hop (Km)

PTX PRX(NOM)

PRX(NOM) = PRX(Th) + FM




1 - 2 - 56


Exercise

Exercise 1 - PRx threshold

Calculate the 10-6 BER PRx threshold in the following system:

Digital signal : STM1Modulation type : 128 QAM (S/N at 10-6=26.7 dB)Redundancy : 6.7%Noise figure : 4 dB

Note: Use the Nyquist bandwidth.




1 - 2 - 57


Signature measurement [cont.]

The sensitivity of a digital radio equipment to multipath distortions can be estimated by laboratory measurements (”Equipment Signature").The Tx signal passes through a simulated multipath channel, modelled by a direct path plus echo. This produces a frequency selective response:

Notch Depth = maximum Fade Depth within the signal bandwidth;

Notch Frequency = notch position, relative to the signal carrier.

Notch depth[dB]

Relative Notch Position [MHz]-10 -5 0 5 10 15-15

BER < 10-3

BER > 10-3

The Notch Depth and Frequency are varied (adjusting amplitude and phase of direct and echo signals). In each condition the Bit Error Ratio (BER) is measured. In the Notch Depth / Notch Frequency plane, the Signature gives the region (Notch parameters) with BER > 10-3 (or any other threshold). The area below the Signature gives ameasure of the receiver sensitivity to multipath distortions.




1 - 2 - 58


Signature measurement [cont.]

In order to simulate in the laboratory the distortions produced during multipath fading events a two-ray channel model is usually adopted.

Signature test bench:

= echo signal delay

= echo signalphase shift (relativeto the direct signal)

b = echo signal amplitude

MOD

Tx Y +

Delay Phase Att

b

Patterngenerator

Rx

DEM

Errordetector

τ ∅

τ

∅

Amplitude = 1




1 - 2 - 59


Signature measurement

Measurement Procedure:

The Bit Error Rate (BER) is measured by comparing the bit stream at the Tx input with the one estimated at the receiver. The following steps must be performed:

a) Set the echo delay to a positive value t (to get a minimum phase signature).

b) Set the echo phase to the value corresponding to Notch Frequency f o = Fc - Δ F (Fc = carrier frequency, 2 D F = bandwidth to be explored).

c) Starting with b= 0, increase the Notch Depth B; stop when the BER reaches a giventhreshold (usually 10-3). This is the Critical Notch Depth B c for that BER value.

d) The point [Bc ,fo] is a Signature point, to be plotted in the Notch Depth vs. NotchFrequency plane.

e) Move the Notch Frequency fo of a given frequency step. Repeat steps c), and d) until fo = Fc + Δ F (the band to be explored is completed).

f) Repeat steps b) to e) with a negative delay (to get a non- minimum phase signature).




1 - 2 - 60

Blank Page





1 - 2 - 61

5 Propagation during rain




1 - 2 - 62


Propagation during rain [cont.]

Main phenomena associated to Radio Propagation in the presence of Rain:

Scattering: part of the EM energy is re-irradiated by the raindrops in every directions.

Absorption: part of the EM energy is transferred to the water molecules in the raindrops.

De-polarization: the polarization plane (e. g. Vertical) of the incident radio signal is rotated, thus producing a cross- polarized (e. g. Horizontal) component in the signal at the receiver.

These phenomena depend on:Signal Frequency (wavelength compared to the drop size)Signal Polarization (due to the non-spherical drop)Rain Intensity.




1 - 2 - 63


Propagation during rain

Effect of Scattering: The scattering of radio wave energy produced by rain drops may cause interference to other radio systems. This effect is particularly significant with high Tx power (e. g. interference from satellite earth stations to radio- relay links). The procedures for the evaluation of the Co-ordination Area around Earth Stations (ITU- R Rec. 615) include an estimate of this effect.

Effect of Absorption: The absorption of the radio wave energy causes an attenuation on the Rx power.

Effect of De-polarization: In radio links using the co-channel plan (two cross-polar radio channels at the same frequency) the C/ I ratio is guaranteed by the isolation between H and V polarizations. In the absence of rain, the antenna XPD can provide a C/ I ratio well above 25dB.The Rain de-polarization reduces the C/ I ratio at the receiver. A statistical model is proposed by ITU- R Rec. 530. Example: In a 13 GHz link, with 40 dB rain attenuation, the XPD is reduced to about 16 dB (according to the ITU model).




1 - 2 - 64


Attenuation by rain [cont.]

Attenuation can also occur as a result of rain for frequencies higher than 5 GHz.

A technique for estimating long-term statistic of rain attenuation is reported in ITU 530-7.

The following technique is used for estimating the long-term statistics of rain attenuation:

Step 1: Obtain the rain rate R0.01 exceeded for 0.01% of the time (with anintegration time of 1 min). If this information is not available from localsources of long-term measurements it is possible to refer to thefollowing table (Rec. ITU-R P.837).




1 - 2 - 65



Rain intensity exceeded for 0.01% of the time (R0.01)

Percentageof time (%) A B C D E F G H J K L M N P Q

1

.3

.1

.03

.01

.003

.001

<0.1

<0.8

<2

<5

<8

14

22

0.5

2

3

6

12

21

32

0.7

2.8

5

9

15

26

42

2.1

4.5

8

13

19

29

42

0.6

2.4

6

12

22

41

70

1.7

4.5

8

15

28

54

78

3

7

12

20

30

45

65

2

4

10

18

32

55

83

8

13

20

28

35

45

55

1.5

4.2

12

23

42

70

100

2

7

15

33

60

105

150

4

11

22

40

63

95

120

5

15

35

65

95

140

180

12

34

65

105

145

200

250

24

49

72

96

115

142

170




1 - 2 - 66



Rainfall Regions - Europe, Africa and Asia




1 - 2 - 67



Step 2: Compute the specific attenuation, γR (dB/km) for the frequency,polarization and rain rate according to the relationship

and the data (depending on frequency and polarization) enclosed in the following table.

α0.01R Rkγ =




1 - 2 - 68



FREQ. K (H) K (V) α (H) α (V)

4 0.000650 0.000591 1.121014 1.075118

5 0.001108 0.001019 1.223217 1.158436

6 0.001777 0.001582 1.307902 1.226152

7 0.002897 0.002529 1.334564 1.311525

8 0.004625 0.004021 1.326024 1.312673

11 0.014191 0.012619 1.243525 1.229707

12 0.018810 0.016875 1.217389 1.200131

13 0.024051 0.021738 1.194580 1.173875

15 0.036160 0.033010 1.158202 1.131863

17 0.050182 0.045996 1.131039 1.101352

18 0.057868 0.053060 1.119748 1.089204

20 0.074602 0.068293 1.099966 1.069047

23 0.103276 0.094005 1.073910 1.044816

25 0.124923 0.113187 1.057440 1.030525

27 0.148673 0.134098 1.041143 1.016802

30 0.188249 0.168788 1.016736 0.996539

35 0.264023 0.235197 0.976517 0.962965

38 0.314429 0.279615 0.953212 0.943165

40 0.349597 0.310786 0.938230 0.930273




1 - 2 - 69


Attenuation by rain

Step 3: Compute the effective path length deff of the link by multiplying theactual path length “d” by a distance factor “r”. An estimate of this factoris given by:

Step 4: An estimate of the path attenuation exceed for 0.01% of the time isgiven by:

Step 5: Attenuation exceed for other percentages of time p in the range0.001% to 1% may be deduced from the following power law:

p)0.043log(0.5460.01

10p0.12AA(dB) +−××=

drγdγA ReffR0.01 ==

0dd1

1r+

= ,100)R0.015xmin(0

0.01,35ed −=

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛∗∗

=⇒= 0.12ALog0.5769566-1-16.348837-

0.01R

R10

10pAFMA settingBy (result is in %)




1 - 2 - 70


Rain Unavailability Prediction

From the Time % vs. Rain Attenuation curve, the Unavailability is computed as the time percentage with attenuation greater than Fade Margin. In the Figure the Fade Margin is 30dB. Then the Rain Unavailability is about 0.005%.

0 10 20 30 40 500.001

0.01

0.1

1

FM% o

f Tim

e

Attenuation [dB]

The above curve is valid for Region L, 50 km, 11 GHz and polarization H.




1 - 2 - 71


Exercise

Exercise 1 - Rain unavailabilityCalculate the rain unavailability in the following link:

Region : LDistance : 50 kmFrequency : 11 GHzPolarization : HFade Margin : 30 dB




1 - 2 - 72

6 Propagation model




1 - 2 - 73

6 Propagation model

Fade margin [cont.]

PERFORMANCES ARE RELATED TO RADIO LINK FADE MARGIN

In a well designed Radio Relay Link the Rx Power is close to the designed level for most of the time.The Radio Link is usually designed in such a way that the Received Power “pRx” (normal propagation conditions) is much greater than the Receiver Threshold “pRx Th”.

Fade Margin FM is defined as : FM (dB) = pRx (dBm) - pRx Th (dBm)

A Fade Margin is required to compensate for the reduction in Rx power caused by Fading Activity.The Fade Margin guarantees that the link will operate with expected quality, even if anomalous propagation condition causes Fading Activity “FA”, as long as the Fading Activity is lower than the Fade Margin:

FA < FM




1 - 2 - 74

The Outage condition is present when the Rx power is below the Rx Threshold

Outage probability: P(Outage)= P [pRx < pRx Th]

6 Propagation model

Fade margin

pRx

TIME

FADE MARGIN

NORMAL PROPAGATION

pRx ThTHRESHOLD

OUTAGE ZONE

FADINGACTIVITY




1 - 2 - 75

6 Propagation model

Fading definitions

ATMOSFERICMULTIPATH

FLAT FADING

DIGITALANALOG

THERMALNOISE

THERMALNOISE

FADING EXCEEDSMARGIN OVERTHRESHOLD

SELECTIVEFADING

DIGITALANALOG

INTERMODULATION INTERSYMBOLINTERFERENCE

DISTORSION PRODUCESEYE CLOSURE AND

LOSS OF SYNC.




1 - 2 - 76

6 Propagation model

Exercise

Which is the cause of the multipath fading?RainLayers in the atmosphere




1 - 2 - 77

6 Propagation model

Flat fading outage [cont.]

The Probabilty of having a fade depth A (dB) greater than FM (Fade Margin) is (Rayleigh formula):

P0 = Multipath Occurrence Factor.It is a measure of the multipathactivity in a radio hop.

{ } 10FM

0f 10PFMAProbP−

=>=

0 10 20 30 40 50

0.0001

0.001

0.01

0.1

1

FM [dB]

Pro

bA

> F

M

Curve for P0 = 110 dB/dec




1 - 2 - 78

6 Propagation model

Flat fading outage [cont.]

Occurence Factor “P0” - Alcatel Method

P0 may be measured and directly used or evaluated.

where:a is the climatic coefficientb is the roughness factor

Typical values of "a" are:a = 2.4 for maritime hopsa = 1 for flat hopsa = 0.7 for hill hopsa = 0.3 for mountain hops

km)indGHz;in(fdfba10450d

4fba0.2P 37-

3

0 •••••=⎟⎠⎞

⎜⎝⎛=




1 - 2 - 79

6 Propagation model

Flat fading outage

According to the path profile the roughness factor is: flat irregular

(“S” is defined in ITU-R Rep. 338-5 Table III).

Typical values of ”b" are:b = 0.25 irregular terrainb = 1 medium terrainb = 4 flat terrain

( )m42S61.3-

15Sb <<⎟⎠⎞

⎜⎝⎛=




1 - 2 - 80

6 Propagation model

Exercise

Exercise - Flat fading outage probability

Calculate the outage probability due to the flat fading in the following link:

Flat Fading Margin : 40 dBHop length : 50 kmType of hop : flatFrequency : 8 GHzRoughness (S) : 15




1 - 2 - 81

6 Propagation model

Selective fading outage [cont.]

The reflected ray is characterized by:amplitudedelayphase shift

SELECTIVE FADING

reflected rays

direct ray

refracting layer

a2a1

1

Three-ray and two-ray models

The three-ray model is a model in which the signal at the input of the Rx antenna is the sum of three signals with amplitude:

1 a1 a2The second and third rays are delayed respect to the first by τ1 and τ2 seconds.

The channel transfer function is:

Supposing that τ is very small (at the ω1 and ω2 ends of the band the phase of the reflected ray a1 will not change ω1 τ1 = ω2 τ2) and by setting a2 = ab and τ2 = τ, the three-ray model becomes a two-ray model with

The amplitude of the sum vector depends on ω and varies between a(1-b) and a(1+b).The minimum of |H(w)| (“notch”) is reached when:

ϕ + ω τ = nπ with n = 0, 1 …. N

and the minimum points are frequency-spaced by

If fo is the frequency of the notch closest frequency fc of the carrier

21211)( ωτωτ jj eaeawH −− ++=

)1()( ϕωτ jj ebeawH ±±−=

τ1

τ21

≤− co ff




1 - 2 - 82

6 Propagation model


2 ray amplitude response

ff0fc

a(1-b)

a(1+b)

channelbandwidth

f

20 lg a

-20 lg

30

25

20

15

20 lg (1-b) 20 lg(1+b)(1-b)

1/τ 1/τ

H(ω)H(ω)




1 - 2 - 83

6 Propagation model


2-Ray Group Delay for Fades of 5 dB and 20 dB




1 - 2 - 84

6 Propagation model


The Alcatel method to evaluate the selective fading outage is the signature method

Selective fading outage

where:

Δfo = signature bandwidth [GHz]Bc = notch producting a given BER [dB]Ts = symbol time depending on capacity and modulation [ns]τm = echo delay mean value [ns]

d = hop length [km]τr = reference delay [6.3 ns]

( )2m2s

n τTKη4.3Ps ×⎟⎟

⎠

⎞⎜⎜⎝

⎛××=

( )75.002.0exp1 P×−−=η

2010cB

r

sosn

TfTK−

Δ=τ

[ ]nsdm

3.1

507.0 ⎟

⎠⎞

⎜⎝⎛=τ




1 - 2 - 85

6 Propagation model

Selective fading outage

Signature

Bc




1 - 2 - 86

6 Propagation model

Exercise

Exercise - Selective fading outage probability

Calculate the outage probability due to the selective fading in the link of example 1 with the following data:

Digital signal : STM1Modulation type : 128 QAMRedundancy : 10%Kn : 0.25




1 - 2 - 87

6 Propagation model

Single channel global outage

The outage time can be expressed, in the most general form, as the weighted sum of two different contributions concerning flat and selective fading.

Where “a” is in the range 1.5 to 2: in the case of single channel, for both ITU and ALCATEL a=2.

a2

2a

s2a

f PPP ⎟⎠⎞

⎜⎝⎛ +=




1 - 2 - 88

7 Quality objectives of Digital Radio Links




1 - 2 - 89


Introduction

The link reference objectives and dimensioning criteria are:

AVAILABILITY OBJECTIVES based on:

• Definition of Availability

• Max. Unavailable Time Percentage

ERROR PERFORMANCE OBJECTIVES based on:

• Quality Parameters

• Max. Time Percentages for each quality parameter below given thresholds.

Note: Error Performance Objectives are checked only during Available Time.




1 - 2 - 90


ITU-T recommendations

Rec. G.821 Rec. G.826 Rec. G.828

First Issue 1980 1992 2000

Ref. Connection 27,500 km 27,500 km 27,500 km

Radio link PDH PDH and SDH SDH

Bit Rate Below Primary Rate At or Above Primary At or Above PrimaryRate Rate

(64 kbit/s) (> 2 Mbit/s) (> 2 Mbit/s)

Performance criteria Errored Bits Errored Blocks Errored Blocks

(Media independent Recommendations)




1 - 2 - 91


Error Performance Events

Example of unavailability determination

Time

10 secsec< 10 10 sec

Unavailability detected Availability detected

Unavailable period Available period

Severely Errored Second

Errored Second (non-SES)

Error-free Second

Note: Within brackets is explained the event for G.821.

ES - Errored SecondIf one or more errored block (or bit) events occur within one second, an errored second event is generated.

SES - Severely Errored SecondA one-second period which contains ≥30% of errored blocks (or BER ≥10-3). SES is a subset of ES.

BBE - Background Block/Bit ErrorsAn errored block (or bit) not occuring as part of an SES.

UAS - UnAvailable SecondConsecutive Severely Errored Seconds may be precursors to periods of unavailability. A period of unavailable time begins at the onset of ten consecutive SES events. These ten seconds are considered to be part of unavailable time. The period of unavailable time ends at the onset of ten consecutive non-SES events. These ten seconds are considered to be part of available time.




1 - 2 - 92


Impact of propagation on performance objectives

Performance Impairment Degradation Period Performance Objective

Rain >10 seconds Availability

Multipath Fading < 10 seconds Error Performance (SES)




1 - 2 - 93


ITU-T G.821 [cont.]

ITU starting from an HRDP (Hypotetical Reference Digital Path) refers to three different applicable levels of acceptable connection quality of the transmission digital circuits, belonging to an ISDN environment.

They are representative of a practical national transmission network structure so that each digital radio link can be assigned to one of the following reference circuits, depending on its location within the network.

High GradeThis will encompass long haul national and international connections operatingmainly at high bit rates. These connections will naturally be high grade equipment.

Medium GradeSystems operating between local exchanges in the national network.

Local GradeSystems operating between customers’ premises and local exchanges and typicallyoperating equal to, or lower, than 2 Mbit/s.




1 - 2 - 94


ITU-T G.821 [cont.]

Error performance parameters

Error performance should only be evaluated during connection’s availability periods measuring:

Errored Second Ratio (ESR)

The ratio of ES (one-second period with at least one errored bit) to total seconds in available time during a fixed measurement interval.

Severely Errored Second Ratio (SESR)

The ratio of SES (one-second period with a BER > 10-3) to total seconds in available time during a fixed measurement interval.




1 - 2 - 95

ESR 0.012 0.012 0.032 0.012 0.080.012

SESR 0.00015 0.00015 0.0004 0.00015 0.0010.00015

Objectivesallocation

15% 15% 40% 15% 15%

Localgrade

Mediumgrade

Localgrade

Highgrade

Mediumgrade

T-referencepoint

T-referencepoint

25000 Km1250 Km 1250 Km

27500 Km


ITU-T G.821 [cont.]

G.821 Basic apportionment principles




1 - 2 - 96


ITU-T G.821 [cont.]

High grade Medium grade Local grade

HDRP Rec. F.594PerformanceObjectives Rec. F.697

Real link Rec.F.634

Rec. F.696

HDRP Rec. F.557AvailabilityObjectives Rec. F.1053

Real link Rec. F.695

ITU-R Recommendations (radio specific) G.821 related




1 - 2 - 97


ITU-T G.821 [cont.]

ITU-R Rec. 557

Unavailability objective for HDRP (2500 km) high grade link:

• Unavailability < 0.3 %




1 - 2 - 98


ITU-T G.821 [cont.]

ITU-R Rec. 695

Unavailability objective for high grade real link:

• Unavailability ( )2500kmL%2500

Lx0.3 ≤<




1 - 2 - 99


ITU-T G.821 [cont.]

ITU-R Rec. F.594

Quality performance for the HDRP (2500 km) should not exceed thefollowing values.

• SES< 0.054% = 0.004% + 0.05%

• ES < 0.32%




1 - 2 - 100

ITU-R Rec. 634High grade real link

Quality performance should not exceed the following values scaled depending on the link length

•

•

( )2500kmL0.054%x2500

LSES ≤<

( )2500kmL0.32%x2500

LES ≤<


ITU-T G.821 [cont.]




1 - 2 - 101


ITU-T G.821

ITU-R Rec. 696

Medium grade real links are divided in 4 quality classes with different objectives:

Performance Percentage of any monthParameters

M.G. M.G. M.G. M.G.Class 1 Class 2 Class 3 Class 4280 km 280 km 50 km 50 km

Unavailability 0.033 0.05 0.05 0.1

SES 0.006 0.0075 0.002 0.005

ES 0.036 0.16 0.16 0.4




1 - 2 - 102


Rec. ITU-T G.826 and G.828 [cont.]

G.826 - Error performance parameters and objectives for international, constant bit rate digital paths (PDH and SDH) at or above the primary rate over a 27500 km HRP.

G.828 - Error performance parameters and objectives for international, constant bit rate synchronous digital paths (SDH) over a 27500 km HRP.

They are:• Media Independent

• Fix Quality Obj. (Availability Obj. by G.827)

• Basd upon error performance measurements of blocks




1 - 2 - 103



Definition of block

A block is a set of consecutive bits.

The blocks are defined for:

path by G.826 and G.828 for path based on SDH

MS and RS by G.829 (that gives only definitions, not objectives)




1 - 2 - 104



G.826-G.828 Error Performance Events

Errored Block (EB): 1 block with at least 1 errored bit

Errored Second (ES): 1 second period with at least one errored block or at least one defect(*)

Severely Errored Second (SES): 1 second containing more than 30% errored blocks or at least one defect(*)

Background Block Error (BBE): 1 errored block not belonging to a SES

G.828 introduces two additional error performance events, SEP(Severely Errored Period, sequence of between 3 to 9 consecutive SES) and SEPI (SEP Intensity) → SEP and SEPI values tbd

(*) e.g.: LOS, AIS, LOF




1 - 2 - 105



Errored performance should only be evaluated whilst the path is in the available state

Errored Second Ratio (ESR). The ratio of ES in available time to total seconds in available time during a fixed measurement interval

Severely Errored Second Ratio (SESR): The ratio of SES in available time to total seconds in available time during a fixed measurement interval

Background Block Error Ratio (BBER): The ratio of BBE in available time to total blocks in available time during a fixed measurement interval excluding all blocks affected by SESSEPI (Severely Errored Period Intensity): The number of SEP events during available time, divided the total available time




1 - 2 - 106



G.826/G.828 Error performance objectiveGlobal error performance objectives for 27,500 HRP

Mbit/s 1.5 - 5 5 - 15 15 - 55 55 - 160

ESR 0.04 0.05 0.075 0.16

G.826 SESR 0.002

BBER 2*10-4

ESR 0.01 0.01 0.02 0.04

SESR 0.002

G.828 BBER 5*10-5 5*10-5 5*10-5 5*10-5

SEP t.b.d.




1 - 2 - 107



Rec. ITU-T G.826 and G.828

The choice of G.826 or G.828 objectives depends on a mutual agreement between the parties: the path fails to meet the error performance requirement if any of these objectives is not met

The actually suggested evaluation period is 1 month: in cases where 1 month evaluation period may not permit accurate statistical estimation, a longer evaluation period (up to 1 year) may be used.

Compliance with the performance specification of these Recommendations will, in most cases, meet the G.821 requirements

Note that G.828 has same SESR objective than G.826 but more stringent ESR and BBER objectives

SDH paths meeting the G.828 will ensure ATM traffic to meet I.356




1 - 2 - 108

Total objectives100%

27500 km

Country basedportion 45%

Distance basedportion 55%

National portion35%

International portion10%

1% each 500 km (G.826)0.2% each 100 km (G.828)

Terminatingcountry 1% (2)

Transitcountry 2% (4)



G.826-G.828 Basic apportionment principles




1 - 2 - 109

1%

Objectivesallocation

17.5%

PEP

Terminatingcountry

27500 Km

Nationalportion

NationalportionInternational portion

10% 17.5%

2% 2% 2% 2% 1%

PEP

45%

Transitcountries

Terminatingcountry



G.826/G.828 Country based apportionment




1 - 2 - 110



G.826-G.828 - Allocation to the National/International Portion of the end-to-End path

For each national portion are allocated a fixed block allowance of 17.5% of the end-to-end objective

For the international portion is allocated a block allowance of 2% per intermediate country plus 1% for each terminating country

In both cases a distance-based allocation is added to the block allowance in terms of 1% per 500 km (Rec. G.826) or 0.2% per 100 km (Rec. G.828)

The added distance-based allocation is rounded up to the nearest 500 km for Rec. G.826 and to the nearest 100 km for Rec. G.828




1 - 2 - 111


Rec. ITU-T G.826 and G.828

G.826-G.828 related recommendations

F. 1703F.1493F.1492Radio

Real Link

G.827G.827G.827HDPAvailability objectives

F. 1668F.1491F.1397

Path & Mpx/Reg.sections

F.1189F.1092PathPerformance objectives

Final omni inclusive Recomendations

National portion

International portion




1 - 2 - 112


Rec. ITU-T G.826 and G.828 - ITU-R F.1092 [cont.]

F.1092: Error Performace Objectives for path on digital Radio, International portion of 27500 km HRP

The G.826-8 objective is subdivided into:

Distance allocation factor: FL = 0.01 x L/500 L(km)

Block allowance factor BL (LREF value is provisionally 1000 km) defined as:

Intermediate country Terminating country

Where: BR = Block allowance ratio (0 < BR < 1)

Lmin = 50 km

REFminREF

RL LLLifL

Lx.02xBB <<=

REFRL LLif.02xBB >=

2LLLif

2/LLx.01xBB REF

minREF

RL <<=

2/LLif.01xBB REFRL >=




1 - 2 - 113


Rec. ITU-T G.826 and G.828 - ITU-R F.1092 (International, Path)

Stating A = FL + BL the table lists the new objectives

Mbit/s 1.5 - 5 5 - 15 15 - 55 55 - 160 >160

ESR .04*A .05*A .075*A .16*A Under Study

SESR .002*A

BBER .0002*A




1 - 2 - 114



F.1397: Error Performance Objectives for real digital radio links in the international portion of 27500 km HRP

Defines a rule in order to indicate the objectives based on real link length and it should be used for path, multiplex and regenerator sections performances according to the parameters defined in G.826-828 for path and G.829 for multiplex and regenerator sections.

EPO = Bj (Llink / LR) + Cj

where:

LR = 2500 km, Lmin = 50 km

j=1 for Lmin < L < 1000 km, j=2 L > 1000 km for intermediate country

j=3 for Lmin < L < 500 km, j=4 L > 500 km for terminating country




1 - 2 - 115

Parameter Bit rate Lmin < Llink < 1000 km 1000 km < Llink

(Kbit/s) B1 C1 B2 C2

ESR 1664 5 x 10-4 (1+BR) 0 5 x 10-4 2 x 10-4 x BR

ESR 2240 5 x 10-4 (1+BR) 0 5 x 10-4 2 x 10-4 x BR

ESR 6848 5 x 10-4 (1+BR) 0 5 x 10-4 2 x 10-4 x BR

ESR 48960 10-3 (1+BR) 0 10-3 4 x 10-4 x BR

ESR 150336 2 x 10-3 (1+BR) 0 2 x 10-3 8 x 10-4 x BR

SESR 1664-150336 10-4 (1+BR) 0 10-4 4 x 10-5 x BR

BBER 1664-48960 2.5 x 10-6 (1+BR) 0 2.5 x 10-6 10-6 x BR

BBER 150336 5 x 10-6 (1+BR) 0 5 x 10-6 2 x 10-6 x BR



Parameters for the EPO for Intermediate countries according to G.828




1 - 2 - 116



Parameters for the EPO for Terminating countries according to G.828



ESR 1664 5 x 10-4 (1+BR) 0 5 x 10-4 10-4 x BR

ESR 2240 5 x 10-4 (1+BR) 0 5 x 10-4 10-4 x BR

ESR 6848 5 x 10-4 (1+BR) 0 5 x 10-4 10-4 x BR

ESR 48960 10-3 (1+BR) 0 10-3 2 x 10-4 x BR

ESR 150336 2 x 10-3 (1+BR) 0 2 x 10-3 4 x 10-4 x BR

SESR 1664-150336 10-4 (1+BR) 0 10-4 2 x 10-5 x BR

BBER 1664-48960 2.5 x 10-6 (1+BR) 0 2.5 x 10-6 5 x 10-7 x BR

BBER 150336 5 x 10-6 (1+BR) 0 5 x 10-6 10-6 x BR




1 - 2 - 117



ESR 1.5-5 2 x 10-3 (1+BR) 0 5 x 10-4 8 x 10-4 x BR

ESR >5-15 2.5 x 10-3 (1+BR) 0 5 x 10-4 10-3 x BR

ESR >15-55 3.75 x 10-3 (1+BR) 0 5 x 10-4 1.5 x 10-3 x BR

ESR > 55-160 8 x 10-3 (1+BR) 0 8 x 10-3 3.2 x 10-3 x BR

ESR >160-3500 under study

SESR 1.5-3500 10-4 (1+BR) 0 10-4 4 x 10-5 x BR

BBER 1.5-3500 10-5 (1+BR) 0 10-5 4 x 10-6 x BR



Parameters for the EPO for Intermediate countries according to G.826




1 - 2 - 118


Rec. ITU-T G.826 and G.828 - ITU-R F.1397

Parameters for the EPO for Terminating countries according to G.826



ESR 1.5-5 2 x 10-3 (1+BR) 0 2 x 10-3 4 x 10-4 x BR

ESR >5-15 2.5 x 10-3 (1+BR) 0 2.5 x 10-3 5 x 10-4 x BR

ESR >15-55 3.75 x 10-3 (1+BR) 0 3.75 x 10-3 7.5 x 10-4 x BR

ESR > 55-160 8 x 10-3 (1+BR) 0 8 x 10-3 1.6 x 10-3 x BR

ESR >160-3500 under study

SESR 1.5-3500 10-4 (1+BR) 0 10-4 2 x 10-5 x BR

BBER 1.5-3500 10-5 (1+BR) 0 10-5 2 x 10-6 x BR




1 - 2 - 119



F.1189: Error Performance Objectives for digital path carried by digital radio, national portion of a 27500 km HRP.

It concerns the national portion of the HRP that is subdivided into three basic sections

Access

Short haul

Long Haul

Performance objectives are fixed for each of the three types of link, just for path level, according to the following table

PEP LE PC/SC/TC IG

Access ShortHaul

LongHaul




1 - 2 - 120



The values for the B parameter are fixed as following:

⇒ A1 + .001*L/500 long haul ( 1%<A1<2%)

⇒ 7.5%<B<8.5% short haul

⇒ 7.5%<B<8.5% access

Mbit/s 1.5-5 5-15 15-55 55-160 >160

ESR .04*B .05*B .075*B .16*B ?

SESR .002*B .002*B .002*B .002*B .002*B

BBER .0002*B .0002*B .0002*B .0002*B .0002*B

The values indicated can be reallocated in different way within the national portion of the network taking into account that:

the sum of the 3 contributions shall not exceed 17.5%

the sum resulting from short and long haul contributions are in the range 15.5% to 16.5%.




1 - 2 - 121



F. 1491: Error performance objectives for real digital radio links, national portionof a 27500 km HRP

Defines a rule in order to indicate the objectives based on real link length and it should be used for path, multiplex and regenerator sections performances.

The national portion is subdivided into three categories: the access section, the short haul section and the long haul section.

The parameters used for the performance objectives are defined in

G.826-828 for path section

G.829 for multiplex and regenerator sections




1 - 2 - 122



Long haul

A = A1 + 0.00002 x Llink for Llink > 100 km

where A1 provisionally been agreed in 0.01<A1<0.02

Short haul and access: 7.5% < A < 8.5%

Mbit/s 1664 2240 6848 48960 150336VC-11 TC-11 VC-12 TC-12 VC-2 TC-2 VC-3 TC-3 VC-4 TC-4

ESR 0.01*A 0.01*A 0.01*A 0.02*A 0.04*A

SESR 0.002*A 0.002*A 0.002*A 0.002*A 0.002*A

BBER 5*A*10-5 5*A*10-5 5*A*10-5 5*A*10-5 1*A*10-4

( ) 100kmL50kmfor 100Lx0.002AA link

link1 <<+=




1 - 2 - 123


Rec. ITU-T G.827

G.827 - Availability parameters and objectives for end-to-end international constant bit-rate digital paths

Gives two kind of objectives: • Availability ratio

• Outage intensity

The objectives are dependents by length and by categories (National or international path elements)

For both objectives “mean” and “worst” values are given




1 - 2 - 124


Rec. ITU-T G.827 [cont.]

Relevant to G.827 parameters and objectives, ITU-R derived these recommendations:

Rec. F.1492: Availability Objectives for real Digital Radio-relay links forming part of international portion constant bit rate digital path at or above primary rate

Rec. F.1493: Availability Objectives for real Digital Radio-relay links forming part of national portion constant bit rate digital path at or above primary rate

and, to include and substitute both the above, recently approvedRec. F.1668: Error performance objectives for real digital fixed wireless

links used in 27 500 km hypothetical reference paths and connections




1 - 2 - 125


Exercise

Exercise 1 - Unavailability Calculate the unavailability objective due to

the propagation in a 60 km link (using Rec. 695).

Exercise 2 - SES calculationCalculate the allowed SES by using G.826 (F.1092) in the following link:

Link lenght : 50 kmType of country : intermediate countryBlock Allowance Ratio : 1




1 - 2 - 126

8 Fading countermeasures




1 - 2 - 127


Adopted techniques

Techniques adopted to reduce the multipath fading impairment:Adaptive Signal Equalization at the ReceiverDiversity Reception:

• Space Diversity• Frequency Diversity• Angle Diversity




1 - 2 - 128


Adaptive equalization [cont.]

An Adaptive Equalizer is a circuit used at Rx, to partially compensate for signal distortion. Adaptativity means that the equalizer response is modified, depending on the received signal.

In the Intermediate Frequency (IF) implementation, the equalizer amplifies the spectral components more deeply attenuated by fading.

In the Base Band (BB) implementation, the equalizer cancels from each signal sample the component due to Inter-Symbol Interference (ISI). This technique is usually more effective.

The effectiveness of a signal equalizer can be appreciated by comparing the receiver signatures with and without the equalizer.The reduction in the area below the signature curve gives a measure of the improvement provided by the equalizer.




1 - 2 - 129


Adaptive equalization [cont.]

Notch Frequency [MHz]-10 -5 0 5 10 15-15

Without Equalizer

With EqualizerN

otch

Dep

th [d

B]




1 - 2 - 130


Diversity Improvement [cont.]

In order to improve link performance diversity scheme can be adopted.

Using more than one receiver the outage probability can be significantly reduced.

The diversity configurations are:Frequency diversity (two receivers)Space diversity (two receivers and two antennas)Space and Frequency diversity (two receivers and two antennas) Space and Frequency diversity (four receivers and two antennas)

The diversity can be performed by means of:BB switch (best channel selection)IF combiner that adds the two signals elaborated with a suitable algorithmBB switch and IF combiner

In a diversity configuration the probability that BER exceeds performance objective depends on:

single channel performancecorrelation between the bearersmultipath fading probability




1 - 2 - 131



TWO RECEIVERS DIVERSITY

Diversity parameter m relevant to “order two diversity” is defined:

where η is the multipath activity parameter

The outage probability for a protected channel is:

The corresponding improvement is:

where “Pi” is the probability without protection

( )2K1ηm −=

( )m

PP10BERP jin

DIV

•=> −

iDIV

i

Pm

PPI ==




1 - 2 - 132



a) Frequency diversity

ΔF = frequency diversity [GHz] τm = median hop delay [ns] = where d = hop length [km]

b) Space diversity

S = antenna separation [m] (Max. = 200 λ in this formula) λ = wavelenght [m]

c) Space and frequency diversity (2 receivers)In this case two antennas are used, but the two receivers are at a different frequency. The diversity needs a BB switch and the correlation coefficient considers separatly the two effects and so:

If four antennas are used to obtain the space diversity also in the other side, the formula is:

( )m2f τΔF0.9-expK ••=

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛−= ••

−2

62s λ

S104expK

2f

2s

2fs KKK •=

2f

2s2

2s1

2fs KKKK ••=

1.3

50d0.7 ⎟⎠⎞

⎜⎝⎛




1 - 2 - 133



SPACE AND FREQUENCY DIVERSITY (4 RECEIVERS)

To analyze these configurations we need to extend the definitions given dealing with order two diversity to the case of order four diversity schemes; so the diversity parameters “m” becomes

where η is the multipath activity parameter

Stating that Kij is the correlation coefficient between “i” and “j” channels

43

4 Kdetηm •=

1KKKK1KKKK1KKKK1

Kdet

434241

343231

242321

141312

4 =




1 - 2 - 134


Diversity Improvement

As shown in the figure, there are two possibilities for this configuration including, or not, a space diversity on both sides: space diversity correlation in transmission is generally given by ks1 and its value will be 1 in the case in which there is only one antenna.

Space diversity in Tx side can be applied ONLY in 1+1 configuration.

1

4

2

3

S2S1

f1

f2




1 - 2 - 135


Frequency diversity

Multipath fading is frequency selective. In multi-channel radio systems (usually with about 20 - 30 MHz spacing), not all the RF channels are deeply faded at the same time.

An RF stand- by channel is usually available (in 1+ 1 or N+ 1 arrangement) for equipmentfailure. It can be exploited also for multipath protection.

The traffic of a low quality (deeply faded) working channel can be switched to the stand-by channel, with high probability of a significant quality improvement.

In some cases, the stand-by channel can be in a different RF band (Cross-band frequency diversity). Example: 7 GHz system with 11 GHz protection.

Fast quality detector and switching circuits are required (Hitless Switching: without errors or frame loss caused by the switching itself).

Tx1

f1

Tx2

f2

Rx1

Rx2

Dem

Dem

BB

BB




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Exercise

Exercise - Frequency diversity improvement

Calculate the frequency diversity improvement by using the following data:

Frequency : 8 GHzHop lenght : 50 kmFrequency diversity : 40 MHzMultipath occurrence factor Po : 1Outage probability without protection (10-4) : 0.0001




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Space diversity

Two antennas are usually arranged on a single structure, with a suitable vertical spacing. Typical spacing: 150 - 200 wavelengths.

The correlation of fade depth at the two antennas decreases as the antenna spacing increases. Thus the probability of deep fading at the two antennas at the same time can be made sufficiently low, with a suitable antenna spacing.

Tx1

f

f

Rx1

Rx2

S

Dem

Dem

BB

BB




1 - 2 - 138


Exercise

Exercise - Space diversity improvement

Calculate the space diversity improvement by using the following data:

Vertical antenna separation : 8 mFrequency : 8 GHz

(λ=3.75 cm)Multipath occurrence factor Po : 1Outage probability without protection : 0.0001




1 - 2 - 139


Space and frequency diversity [cont.]

a) 2 Receivers

f1

f2

Rx1

Rx2

S

Diversity in reception side only

Tx1f1

Tx2

Diversity in transmission and reception sides

Tx1

Tx2

Rx1

Rx2

S2

f2

S1

Dem

Dem

BB

BB

Dem

Dem

BB

BB




1 - 2 - 140


Space and frequency diversity

b) 4 Receivers3/f2

4/f2

Rx1

Rx2

1+1 configurations with 4 receivers

Tx11/f1

Tx2

Tx1

Tx2

S2

4/f2

F1

F2

F1

F1 DEM

Rx3

Rx4

F2

F2

1/f1

2/f1

Rx1

Rx2

1+1 configurations with 4 receivers and space diversity also in transmission side

F1

F1

Rx3

Rx4

F2

F2

S1

3/f2

2/f1

F1

F2

BB

DEM BB

DEM BB

DEM BB




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Angle diversity

Two implementations of Angle Diversity can be considered:Antenna Diversity: Two antennas (of the same type or of different types)side-by-side with slightly different pointing angles.Beam Diversity: One antenna with two feeders, producing beams withdifferent shapes and/or pointing.

In both cases, two beams operate at the receiver, closely spaced, but with different shapes. The multipath components are subject to different weighting at the two beams and the two composed Rx signals are in some measure uncorrelated.

Advantages: No need of high, complex tower structures; only one antenna withBeam Diversity; lower costs.

Disadvantages: Less diversity improvement.




1 - 2 - 142

9 Reflections from ground




1 - 2 - 143


Reflections from ground

Depending on the Path Profile, a part of the Tx radio signal can be reflected by the ground toward the Rx antenna. At the receiver, in addition to the direct signal (D), arrives a reflected signal (R).The presence of a ground reflection can be rather critical :

Fluctuations in the Rx signal level, even for long time periodsEnhancement of Multipath Activity (the reflected signal is not added to a stable direct signal, but to the fast-varying multipath signal)Reduction of Space Diversity effectiveness as a countermeasure to multipath.

Reflections should be avoided by:

Route Planning (in particular over-water paths)

Site Selection: Obstruction of the reflected ray can be obtained in some cases, by suitable selection of the radio sites and of antenna heights.




1 - 2 - 144


Geometrical model

Tx

PR1 R2

D1

2

α

α

γγ

Geometrical parameters related to the Reflection mechanism:• Reflection point P• Grazing angle γ• Direct path length D• Reflected path length R1+ R2• Angles a1, a2 between Direct and Refl. Rays

These parameters are varying with time, because of varying propagation conditions (k-factor).




1 - 2 - 145


Rx signal with reflection

In the presence of reflection, the overall received signal (S) is given by the (vectorial) addition of the direct (D) and the reflected (R) signals:

S = D + R

The result of adding the two vectors D and R depends on:Relative amplitude of D and R:

• reflection loss: depends on the surface type (worst case: 0 dB e. g. water)• divergence factor: due to the spherical earth surface (usually a small loss)• antenna directivity: depends on path geometry and antenna beamwidth.

Phase shift between D and R:• direct and reflected path length difference (expressed in multiples of the

wavelength λ; 360 deg. phase shift for each λ)• reflection shift: depends on frequency, grazing angle, and surface type

(usually close to 180 deg).


If the antenna height is varied, then the path length difference and the phase shift between the Direct and the Reflected signal change. As a result, the Rx signal level is a function of the antenna height.

Direct and Reflected signals co-phased Maximum Rx levelDirect and Reflected signals phase-opposed Minimum Rx level

The exact positions corresponding to the maximum and minimum Rx level change with propagation conditions (k-factor).



1 - 2 - 146


Rx signal level

Rx Level

TxRx




1 - 2 - 147


Exercise

Why does the reflected ray from the ground change?




1 - 2 - 148


Space diversity in reflection paths

The Rx level varies with the antenna height, but the position of the maximum Rx level is not stable, due to varying propagation conditions (k- factor). With two antennas, a good Rx level can be expected at least at one antenna.

Space Diversity Engineering:Antenna Spacing: The optimum value is computed, but it depends on the k-factor. Design Rule: Compute Spacing for k= 4/ 3 and check for higher and lower k-factors.Position of the lower antenna: In general, as low as possible, in order to:

Obstruct (at least partially, if possible) the reflected rayClearance:

• For the Lower Antenna, in most cases, Clearance= 0 is enough;• Usual rules for the Higher Antenna.

Implementation Options:BB Switching to the best signalIF Adaptive Combining (as for Multipath countermeasure)RF Combining (Anti-Reflection System).




1 - 2 - 149


Exercise

In the space diversity configuration is the antennaseparation vertical or horizontal?




1 - 2 - 150

10 Frequency re-use




1 - 2 - 151

10 Frequency re-use

Introduction [cont.]

Polarization is the characteristic of electromagnetic wave related to the orientation and rotation of the electrical (E) or magnetic (H) vector.




1 - 2 - 152

10 Frequency re-use

Introduction

Polarization is a very convenient and simple method to enlarge the isolation between two signals increasing the spectrum usage.

Isolation (XPI) of 30 - 40 dB can be obtained adopting available antennas.

By using orthogonal polarization, two independent channels using the same frequency can be transmitted over a single link.

However, during fading periods, the cross-polarization discrimination (XPD) is reduced and significant interference from adjacent or re-used channel can be observed.

Cross Polar Interference Cancellers (XPIC) are used to reduce the effects of cross-polar interference.




1 - 2 - 153

10 Frequency re-use

Terminology

Definition of cross-polarization terms (ITU-R P.310):

Cross-polarization The appearance, during the propagation, of a polarizationcomponent which is orthogonal to the expected polarization.

Cross-polarizationdiscrimination For one radio wave transmitted on a given polarization, the ratio at

the reception side of the power received with the expectedpolarization to the power received with the orthogonal polarization.

Note - the cross-polarization discrimination depends both on thecharacteristics of the antenna and on the propagation medium.

Cross-polarizationisolation For two radio waves transmitted with the same frequency with the

same power and orthogonal polarization, the ratio of the co-polarized power in a given receiver to the cross-polarized power inthat receiver.

Depolarization A phenomenon by virtue of which all or part of the power of a radiowave transmitted with a defined polarization may no longer have adefined polarization after propagation.




1 - 2 - 154

10 Frequency re-use

Exercise

What is the difference between XPD and XPI?




1 - 2 - 155

10 Frequency re-use

Concepts

Frequency reuse of the same RF channels:

The RF frequency channel is used in Vertical and in Horizontal polarization, with two different transceivers.

Single antenna, double polarity or Double antenna, single polarity

Double the RF spectrum traffic capacity

RF frequency reuse types:

1. Without interference canceller (low modulation level)2. With interference canceller (high modulation level)




1 - 2 - 156

10 Frequency re-use

Interferences

Interference due to RF re-use:1. Same frequency re-used channel (cross-polar)2. Adjacent frequency re-used channels (co-polar)

Interference level:

The interference level permitted is proportional to:

1. Modulation type2. XPC (Cross Polar Canceller) gain (for cross-polar channel)3. NFD & ATPC (for adjacent channel)

The interference is non stationary

It depends on fading activity




1 - 2 - 157

10 Frequency re-use

Interference types

1. Same frequency re-used channel (cross-polar) example: ch 2 and ch 2r

2. Adjacent frequency re-used channels (co-polar) example: ch 2 and ch (1r & 3r)

Co-channel mode (RF band reused)

Go (Return) Return (Go)z x y

H (V) 1 2r 3 4r N 1' 2'r 3' 4'r N'V (H) 1r 2 3r 4 Nr 1'r 2' 3'r 4' N'r

fo

B




1 - 2 - 158

10 Frequency re-use

Frequency reuse system block diagram

Single antenna, Double polarity

LO

LO

MOD

MODUP

TX

TXUP

CONV

CONV

RX

RX IF

IFDOWN

CONVH

V

DEM&

XPIC

DEM&

XPIC

H

V

IN OUT

CONV

DOWN

DATADATA

OUTDATA

INDATA

LO

H

V

V

H

H H

V V

V

H




1 - 2 - 159

10 Frequency re-use

Same frequency re-used channel (cross-polar)

With the following formula it is possible to calculate the threshold degradation with a given C/I ratio:

1 dB WORSENING DUE TO C/I ON A128 QAM SYSTEM

MODULATION C/N E-3 C/IdB dB

mod 128 QAM 23 30

MODULATION C/N E-3 Rx THRESHOLDdB dBm

mod 128 QAM 23 -71.0

INTERF. CALC. Rx PW XPI XPIC GAIN TOTALdBm dB dB dBm

-30.00 -35.00 -16.00 -81.00C/I = 51 dB

⎟⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜⎜

⎝

⎛ −

+= 10101log10IC

NC

n(dB)Degradatio

THYPICAL THRESHOLD VALUE OF SAME SYSTEM

THYPICAL INTERFERENCE LEVEL OF A CCDPSYSTEM IN NOT FADING CONDITIONS




1 - 2 - 160

10 Frequency re-use

Adjacent frequency co-polar channel interference

EXAMPLE: for 1 dB WORSENING DUE TO C/I

MODULATION C/N E-3 C/IdB dB

mod 128 cross 23 30

INTERF. CALC. PRX NFD TOTALdBm dB dBm

-30.00 30.00 -60.00

With Correlated fading on all the co-polar signals (same antenna).




1 - 2 - 161

10 Frequency re-use

Exercise

What is the difference between C/N and C/I?




1 - 2 - 162

10 Frequency re-use

Prediction of outage due to multipath propagation [cont.]

The combined effect of multipath propagation and the cross-polarization patterns of the antennas governs the reductions in XPD occuring for small percentage of time. To compute the effect of these reductions in link performance the following step-by-step procedures should be used (Rec. ITU-R P.530-7):

Step 1: Compute

XPDg + 5 for XPDg < 35 (5 is the mean field decreasing)

XPD0 =

40 for XPDg > 35

where XPDg is the manufacturer’s guaranteed minimum XPD at boresight for both the transmitting and receiving antennas, i.e., the minimum of the transmitting and receiving antenna boresight XPDs.




1 - 2 - 163

10 Frequency re-use

Prediction of outage due to multipath propagation [cont.]

Step 2: Evaluate the multipath activity parameter (η)

Step 3: Determine

0.7 one transmit antenna

kXP =

two transmit antennas

In the case where two orthogonal polarized transmissions are from different antennas:

vertical separation is “St“(m)

carrier wavelength is “λ” (m)

⎟⎟⎠

⎞⎜⎜⎝

⎛= •

0

xp

Pηk

log10- Q

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛

2t6-

λS4x10- exp 0.3 - 1




1 - 2 - 164

10 Frequency re-use

Prediction of outage due to multipath propagation

Step 4: Calculate the probability of outage Pxp due to clear-air cross-polarization from

where MXPD is the equivalent XPD margin for a reference BER given by:

co-channel without XPIC

MXPD = co-channel with XPIC XPIRF : 15 - 20 dB

adjacent channel

where is the Carrier - To - Interference ratio for a reference BER (10-3)

Step 5: Evaluate the overall outage as the unweighted sum of partial outagesrelated to flat fadding, selective fading and frequency re-use.

Ptot = Pf + Ps + Pxp

10M-

0xp

XPD

10P P •=

IC - Q XPD o

0 +

IC -XPIRF Q XPD o

0 ++

I

C - NFDQ XPD o0 ++

ICo




1 - 2 - 165

10 Frequency re-use

Prediction of outage due to rain effects [cont.]

Intense rain governs the reductions in XPD observed for small percentages of time. For paths on which more detailed predictions or measurements are not available, a rough estimate of the unconditional distribution of XPD can be obtained from a cumulative distribution of the co-polarized rain attenuation CPA using the equi-probability relation:

XPD = U - V(f) log (CPA)

where:

U = U0 + 30 log (f) (U0 ≈ 15)

V(f) = 12.8 f 0.19 for 8 < f < 20 GH

V(f) = 22.6 for 20 < f < 35 GH

Long-term XPD statistics obtained at one frequency can be scaled to another frequency using the semi-empirical formula:

for 4 < f1, f2 < 30 GHz

where:

XPD1 and XPD2 are the XPD values not exceeded for the same percentage of time at frequencies f1 and f2.

The equation is least accurate for large differences between the respective frequencies. It is most accurate if XPD1 and XPD2 correspond to the same polarization (horizontal or vertical).

( )1212 /fflog20XPDXPD −=




1 - 2 - 166

10 Frequency re-use

Prediction of outage due to rain effects [cont.]

Step-by-step procedure for predicting outage due to precipitation effects (Rec. ITU-R P.530-7):

Step 1: Determine the path attenuation, A0,01 (dB), exceeded for 0.01% of the time.

Step 2: Determine the equivalent path attenuation, Ap (dB):

where U and V are obtained previously, C0/I (dB) is the carrier-to-interference ratio defined for the reference BER without XPIC, and XPIRF (dB) is the cross-polarized improvement factor for the reference BER.

If an XPIC device is not used, set XPIRF = 0.

( )( )/VXPIRF/ICUp

010 A +−=




1 - 2 - 167

10 Frequency re-use

Prediction of outage due to rain effects

Step 3: Determine the following parameters:

if m < 40

m =

40 if m > 40

and

valid values for n must be in the range of -3 to 0. Note that in some cases, especially when an XPIC device is used, values of n less than -3 may be obtained. If this is the case, it should be noted that values of p less than -3 will give outage BER < 1 x 10-5.

Step 4: Determine the outage probability from:

[ ]0.01p 0.12A/A log 23.26

( ) /24m-161.23 12.7-n +=

( )2nXPR 10P −=




1 - 2 - 168

11 Interferences




1 - 2 - 169

11 Interferences

Introduction

Interference could arise from:

1 Local sources (Tx coupled via antennas to Rx)

2 Signals belonging to the same system at a common location

3 Signals belonging to the same system from other locations

4 Signals belonging to the same system from other locations through an overreachcondition

5 Different services sharing the same frequency band (interferences generated by radiolinks of other customers)

Depending on frequency spectrum, the interferences can be subdivided into

A Gaussian interferences

B Non Gaussian interferences

Depending on occurrence probability, the interferences can be subdivided into

C Stationary

D Non stationary (depending on fading activity)

E Non stationary (periodic or non periodic, some external sources as radar)




1 - 2 - 170

11 Interferences

Modem performances

Each radio system is characterized by a minimum value of Carrier to Noise C/N and is also characterized by a minimum value of Carrier to Interference C/I.(In the table are shown some values for training purpose only).

C/I causes 1 dB worsening C/I causes 0.5 dB worsening

C/N W/O FEC (dB) AT C/N E-3 & E-6 W/O FEC

AT C/N E-3 & E-6 W/O FEC

10^-3 10^-6 10^-3 10^-6 10^-3 10^-6

mod levelQAM512 33.00 36.50 39.00 42.50 42.00 45.50256 30.00 33.00 36.00 39.00 39.00 42.00128 27.00 30.00 33.00 36.00 36.00 39.0064 24.00 27.00 30.00 33.00 33.00 36.0032 21.00 24.00 27.00 30.00 30.00 33.0016 18.00 21.00 24.00 27.00 27.00 30.00




1 - 2 - 171

11 Interferences

Local sources [cont.]

Transmitter to receiver interference

INTERFERENCE Type "1" SPECTRUM Type "A" for digital to digital or "B" for analog to digital interferenceACTIVITY Type "C"

WEST EASTINTERFERENCETX TO RX

PTx1 PRx2ANTENNA 1 ANTENNA 2

AF1= ATTEN. FEEDER 1 AF2= ATTEN. FEEDER 2

TX1 RX2




1 - 2 - 172

11 Interferences

Local sources

Transmitter to receiver interference: calculation example

INTERFERENCE CALCULATIONS TX on RX Type

Site of calculationsWest site As example see A, BEast Site

INPUT DATA (example) OUTPUT DATAPTX1 Power TX at radio circulator antenna port dBm 30.00 C/I results (at threshold)PRx thr. PRx at threshold 10^-3 dBm -72.00 level of C/I West on East dB 28.00 BAF1 Attenuation feeder West dB 0.00AF2 Attenuation feeder East dB 0.00D Angle between antennas deg. 80.00 + Threshold 10 -̂3A Attenuation provided by West + East ant dB 130.00 - level of TX West signal on East RXNFD Net filter discrimination (for co-channel) dB 0.00

COMPUTED DATAlevel of TX West signal on East RX dBm -100.00 A + Power TX at radio circulator antenna port

- Attenuation feeder West- Attenuation provided by West + East ant- Attenuation feeder East

FLORENCEMILAN

VENICE

for 2 antennas




1 - 2 - 173

11 InterferencesSignals belonging to the same system at a common location [cont.]

Receiver to receiver interference

INTERFERENCE Type "2"SPECTRUM Type "A" for digital to digital or "B" for analog to digital interferenceACTIVITY Type "D" (depending on fading activity)

WEST EASTINTERFERENCES

Rx to Rx

PR1* PR2*ANTENNA 1 ANTENNA 2

G1= ANTENNA 1 GAIN G2= ANTENNA 2 GAIN

AF1= ATTEN. FEEDER 1 AF2= ATTEN. FEEDER 2

PR1= RX1 INPUT SIGNAL PR2= RX2 INPUT SIGNAL

RX1

* power field at antenna input

RX2

II

WW




1 - 2 - 174

11 InterferencesSignals belonging to the same system at a common location

Receiver to receiver interference: calculation exampleSite of calculations As example see A, B, CWest siteEast Site

INPUT DATA OUTPUT DATAPRx thr. PRx at threshold 10 -̂3 dBm -72.00 Various C/I results (at threshold)G1 Gain antenna West dB 40.00 level of C/I West H on East H dB 25.00G2 Gain antenna East dB 43.00 level of C/I West H on East V dB 28.00AF1 Attenuation feeder West dB 5.00 level of C/I West V on East V dB 25.00AF2 Attenuation feeder East dB 5.00 level of C/I West V on East H dB 28.00PR1 Rec. Power at Rx West dBm -30.00 level of C/I East H on West H dB 26.00 CPR2 Rec. Power at Rx East dBm -30.00 level of C/I East H on West V dB 30.00D Angle between antennas deg. 94.00 level of C/I East V on West V dB 26.00ATTEN Attenuation provided by West antenna HH dB 65.00 level of C/I East V on West H dB 30.00ATTEN Attenuation provided by West antenna HV dB 69.00ATTEN Attenuation provided by West antenna VV dB 65.00ATTEN Attenuation provided by West antenna VH dB 69. + PRX at threshold 10̂ -3ATTEN Attenuation provided by East antenna HH dB 70.00 - level of East H signal on West H ant.ATTEN Attenuation provided by East antenna HV dB 73.00ATTEN Attenuation provided by East antenna VV dB 70.00ATTEN Attenuation provided by East antenna VH dB 73.00BRANC RX branching insertion loss West dB 2.00BRANC RX branching insertion loss East dB 2.00NFD Net filter discrimination (for co-channel) dB 0.00

COMPUTED DATA * power field at antenna inputPR1* Power Rx at antenna direction West dBm -63.00 A Rec. Power at Rx West PR2* Power Rx at antenna direction East dBm -66.00 + Attenuation feeder West

level of West H signal on East H ant. dBm -97.00 - Gain antenna West level of West H signal on East V ant. dBm -100.00 + RX branching insertion loss West level of West V signal on East V ant. dBm -97.00level of West V signal on East H ant. dBm -100.00level of East H signal on West H ant. dBm -98.00

B Power Rx at antenna direction West

level of East H signal on West V ant. dBm -102.00

- Attenuation provided by East antenna HH

level of East V signal on West V ant. dBm -98.00

+ Gain antenna East

level of East V signal on West H ant. dBm -102.00

- Attenuation feeder East- Net filter discrimination (or filter attenuation)- RX branching insertion loss East

FLORENCEMILAN

VENICE




1 - 2 - 175

11 Interferences

Signals belonging to the same system from other locations

Interfered signal received power

PRXCW = PTXAW - BTXAW + GTXAW - FSLAC + GRXCW - BRXC

Interfering signal received power

PRXCint = PTXAint - BTXAint + GTXAint - DGTXAint - NFD - FSLAC + GRXCW - BRXC

INTERFERENCE Type "3"SPECTRUM Type "A" for digital to digital or "B" for analog to digital interferenceACTIVITY Type "D"

B A

Cw

I




1 - 2 - 176

11 InterferencesSignals belonging to the same system from other locations through an overreach condition

Interfered signal received power

PRXDW = PTXCW - BTXCW + GTXCW - FSLCD + GRXDW - BRXD

Interfering signal received power

PRXDint = PTXBint - BTXBint + GTXBint - DGTXBint - NFD - FSLBD + GRXDW - DGRXDint - BRXD

INTERFERENCE Type "4"SPECTRUM Type "A" for digital to digital or "B" for analog to digital interferenceACTIVITY Type "D"

B A

D

w

I

Iw

E F

C




1 - 2 - 177

11 Interferences

Exercise

Exercise - Threshold degradation

Calculate the threshold degradation due to a -95 dBm co-channel interference signal on the following system.

Rx threshold = -72 dBm

dB23NC=




1 - 2 - 178

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1 - 2 - 179

End of Module



2.1 Design exercises3FL 42104 AAAA WBZZA Edition 3 - July 2006

Design exercises


Network planning - Design exercises


2 - 1 - 2

Blank Page





2 - 1 - 3

Objectives

To be able to execute final exercises, useful to recapitulate all the topics explained in Section 1.




2 - 1 - 4

Objectives [cont.]





2 - 1 - 5

Table of Contents


1 Design exercises 7Exercise 9End of Module 10




2 - 1 - 6


Switch to notes view!





2 - 1 - 7

1 Design exercises




2 - 1 - 8

1 Design exercises

Final Exercises

Exercise - 1Check if the following link meets the unavailability (F.695)and quality recommendation (F.1092) (the clearance is 100%).Link data

Length : 60 kmHop type : Flat Roughness : 10 mRainfall region : KType of country : international intermediateBlock Allowance Ratio : 1




2 - 1 - 9

1 Design exercises

Final Exercises [cont.]

Equipment dataChannel configuration : 1+0 (V pol.)Tx power : +32 dBmSymbol frequency : 24.458 Mbit/sRF Frequency : 3890 MHzSignature Kn (10-3) : 0.44510-3 threshold : -74 dBmAntennas (station A & B) : 3 m (40 dBi gain)Feeder in station A : 55 m (2.3 dB/100 m)Feeder in station B : 45 m (2.3 dB/100 m)Branching loss (station A and B) : 3 dBTolerance : 1 dB




2 - 1 - 10

End of Module



3.1 Appendix3FL 42104 AAAA WBZZA Edition 3 - July 2006

Appendix


Network Planning - Appendix


3 - 1 - 2

Blank Page





3 - 1 - 3

Objectives

To be able to understand the modulation concepts.To be able in an example to calculate the unavailability objectivedue to the equipment failures.To be able to understand the general concepts of the M.21xx series and the differences between G.821/826 and M.21xx recommendations.




3 - 1 - 4

Blank Page





3 - 1 - 5

Table of Contents


1 Refresh on modulation concepts 7Modulation Concepts 8BB Transmission 10Bandwidth Formula 11Modulated Signal Spectrum 122-PSK 174-PSK 2016-QAM 2216-TCM 27Performances Versus Noise 30Exercise 31Main Modulation Types Characteristics 32Thermal Noise (C/N versus BER) 33Comparison of Different Mod. Schemes 37Roll-off calculation example 39Blank Page 40

2 Equipment unavailability 41Introduction 43Unavailability objective 44Unavailability of a non-protected section (1+0) 47Unavailability of a protected section (1+1) 50

3 M.21xx-series Recommendations 51End of Module 54




3 - 1 - 6


Switch to notes view!





3 - 1 - 7

1 Refresh on modulation concepts




3 - 1 - 8


Modulation Concepts

Why modulation?

Modulation is necessary to occupy RF narrow bandwidth!

Without modulation (BB transmission) the occupied bandwidth is:

where: fb = bit rateα = roll-off factor

( )α12fBw b +=




3 - 1 - 9


BB Transmission [cont.]

Ideal Transmission Channel

Att. = constant

Rx

Att.

f

f0

0

Tx

-

φ




3 - 1 - 10


BB Transmission

Real Transmission ChannelAtt. = Kost.Att.

f0

Tx Att. =

fc

Rx

32fc

t

2fc

1

Att. = Kost.Att.

f0

Att. =

fc t

1T =

2 13

T TT T

2 13

1fb

T =

fb = Bit rate frequency

1=1fb

2

2fc

2fc

2fc 2=fbfc




3 - 1 - 11


Bandwidth Formula

α = 1.0 α

α = 1.0α = 0.3

α = 0.1

0 < α < 1

α

R(f)

-fC

0.1

r (t)

C

-2fC

0.3

+fC +2fC

a

Antisymmetrical Freq. Responce

acRoll Off = =

R(f)

Ideal Freq. Responce

-T-2T-3T-4T 0 +T +2T +3T +4T

Bw = Bw = fb

Bw = (1+ )

fb2

fb2

-fc +fc




3 - 1 - 12


Modulated Signal Spectrum

V

f

MOD

70 MHz

LOIF

f0

Bw = 2fc

fc 70+fc

f 0

7070-fc

B2fc




3 - 1 - 13


2-PSK [cont.]

2 PSK Modulator

2 PSK Demodulator

DIFF.DEC.

100111

Data

L.O.

IF

IF signal

BTF

1 0

B A

DIFF.ENC.

100111

Data

L.O.

IF

IF signal

PostConversion

Filter

2 PSKMixer

BTF




3 - 1 - 14


2-PSK [cont.]

2-PSK Waveforms - Modulator

DATA IN

1 1 0 1 0 1 1 0 0

CARRIER

IF OUTPUT

+V

-V




3 - 1 - 15


2-PSK [cont.]

2-PSK Waveforms - Demodulator

DATA OUT

1 1 0 1 0 1 1 0 0

CARRIER

IF INPUT

DEMODULATED SIGNAL

-V

+V




3 - 1 - 16


2-PSK [cont.]

Absolute Coding Differential Coding

0 = B 0 = No change in the phase of the carrier1 = A 1 = 180° change in the phase of the carrier

BA1 0

A A

1

B

0

A

1

B

1

B

0

A

1Switch

A A B B A B B A

0 1 0 1 1 0 1

B A B B A B B A

1 1 0 1 1 0 1

RX

ON

TX B

0




3 - 1 - 17


2-PSK

BTF Binary Transversal Filter (digital filter)

β

βIN

H(f)

T5

IN

XA10

T5

XA5

T5

XA2

T5

XA5

A10 X

OUT

A

A/10

A/5T/5

A/2T/5

A/5T/5

A/10T/5

fN-fN-2fN

=10.4

0

fN(1+ ) 2fN

OUT

H(t)

1W- 1

2W- 12W+ 1

W+




3 - 1 - 18


4-PSK [cont.]

4-PSK Modulator 1 0

DIFFER.

ENCODER

IF

PostConvertion

Filter

2 PSKMixer

BTF

L.O.

90°

L.O.

90°

BTF

0010111

2 PSKMixer

SP

L.O.

RFBranching

Filter

Bw = fb (1+ ) Bw = fs (1+ )

fs

0

1

2 PSK fs = fb

4 PSK fs = fb2 22

8 PSK = 3 23

16 PSK = 4 24

B (10) A (00)

C (11) D (01)

fsfb

fsfb

α α




3 - 1 - 19


4-PSK [cont.]

Differential Coding

B B00

B

B

D

B

C

C

D

B

DSwitch

D

11 10 01 11 01 01

ON

= No change

01 = -90° changeTX C

A

A (00)

10 01 11 01 0100

RX B B B C BC10 = +90° change

11 = -180° change

001001110101.........

D (01)

B (10)

C (11)

- +




3 - 1 - 20


4-PSK

4-PSK Demodulator

2 PSKMixer

BTF

L.O.

90°

L.O.

90°

BTF2 PSKMixer

P

S

IF DIFFER.

DECODER

Y1

X1

Y1

X1DecisionCircuit

DecisionCircuit




3 - 1 - 21


16-QAM [cont.]

16-QAM Modulator

11

10

01

00

0100 1110

Vy

Vx

Y1

X1

Y2

X2

Y

X

1 1 +3V

1 0 +1V

0 1 -1V

0 0 -3V

BTF

L.O.

90°

L.O.

90°

BTF

S

P

IFDIFFER.

ENCODER

X2 X2

2RX1 X1

Y2

Y1

X2

X1

Y2

Y1

FEC

X2

X1

Y2

Y1

2R

Y2

2R

Y2

Y1 Y1

2R

X2

X1




3 - 1 - 22


16-QAM

16-QAM Demodulator

BTF

L.O.

90°

L.O.

90°

BTF

P

S

IF DIFFER.

DECODER

X2X2

DecisionCircuit

DecisionCircuit

X2

X1X1X1

Y2Y2Y2

Y1Y1Y1




3 - 1 - 23


16-TCM [cont.]

16-TCM Modulator

BTF

L.O.

90°

L.O.

90°

BTF

S

P

IF

DIFFER.

CONVOL.

X2 X2

2RX1 X1

Y2

Y1

X2

X1

Y2

Y1

MAPPING

X2

X1

Y2

Y1

2R

Y2

2R

Y2

Y1 Y1

2R

X2

X1

+

ENCODER




3 - 1 - 24


16-TCM [cont.]

16-TCM Demodulator

BTF

L.O.

90°

L.O.

90°

BTF

P

S

IF

DIFFER.DECODER

X2X2

DecisionCircuit

DecisionCircuit

X2

X1X1X1

Y2Y2Y2

Y1Y1Y1

VITERBIDECODER

+




3 - 1 - 25


16-TCM [cont.]

TCM Principles - State Diagram (Example with 8-TCM)

SP

ab

S0S1

c

CONVOLUTIONAL ENCODER

S0 S1

0 0

b c0 / 0

S0 S1

0 1S0 S1

1 1

b c0 / 1

S0 S1

1 0

b c1 / 0

b c1 / 1

b c1 / 0

b c0 / 0

b c0 / 1

b c1 / 1




3 - 1 - 26


16-TCM [cont.]

TCM Principles - Mapping (Example with 8-TCM)

1

0

7

65

4

3

2

a

0 1 2 3 4 5 6

0 0 0 0 1 1 1

b 0 0 1 1 0 0 1

0 1 0 1 0 1 0c

7

1

1

1




3 - 1 - 27


16-TCM

TCM Principles - Trellis Diagram (Example with 8-TCM)

0 4

0

4

0

4

0b=0

T0 T1 T2 T3

37

b=1

b=0

15

26

5

1

b=1

37

26

62

04

15

37

0

0 1

1 0

1 1

S0 S1




3 - 1 - 28


Performances Versus Noise [cont.]

2-PSK

CA

= Carrier

N = Noise B

Threshold

1 1C

NC+N

Errors depend of the distance between two points.

We have "ERROR" if N > C N > 1




3 - 1 - 29


Performances Versus Noise [cont.]

4-PSK

2 PSK and 4 PSK have the same performance versus noise, but for this reason is never used 2 PSK due to its double bandwidth

B A

C D

1

1

Two DifferentThreshold

22 = 0.7

2

If the Noise (N) is:

you have error

N > 0.7

ModulationType

2 PSK

4 PSK

ErrorCondition

N > 1

N > 0.7

Bandwidth

BWBW2

(-3dB)

SymbolFreq. (fs)

fbfb2

Noise Power (N) = Amplitde x Bandwidth




3 - 1 - 30


Performances Versus Noise

DEMODULATORIF data

DETECTORERROR

10-6

SN = 13.5 dB

10-6

4 PSK

SN = 18.6 dB

10-6

8 PSK

SN = 20.5 dB

10-6

16 QAM

SN = 26.5 dB

10-6

64 QAM




3 - 1 - 31


Exercise

Why is used the 16 QAM modulation andnot the 16 PSK?




3 - 1 - 32


Main Modulation Types Characteristics

4 PSK

0

8 PSK

0

16 QAM

2.5

64 QAM

3.7

Modulation type

Position of Vectorial modulationstates (levels) at equal peakpower (Cmax)

Peak-to-Mean power ratio (dB)

R/2 R/3 R/4 R/6Nyquist Bandwidth (Bny)Symbol frequency (S)(R = Binary information capacity)

2 3 4 6Modulation efficiency (bit/sec/Hz)(Theoretical)

S/N (dB)(Theoretical at BER = 10-6)

13.5 18.6 20.5 26.5




3 - 1 - 33


Thermal Noise (C/N versus BER)

1 1 0 (normalized)2 PSK

v σ C/N (20log v/σ)Mod.

1 0.70 +3.1 dB4 PSK

1 0.38 +8.4 dB8 PSK

1 0. 19 +14.2 dB16 PSK

0.7 0.23 +9.7 dB16 QAM

0.6 0.10 +15.6 dB64 QAM

0.6 0.047 +22.1 dB256 QAM

16 QAM

σ

Phase leveldecisionthreshold

I

v

Q

v

Q8 PSK

σ

I

б = noise voltagev = carrier peak voltage




3 - 1 - 34


Comparison of Different Mod. Schemes [cont.]

Bit/s(Hz)

6

4

2

10 15 20 25 W (dB)

2 2

4

8

4

8

16

16

BER = 10-6QAM

FSK

64

32

16 QAM 16 PSK

PSK




3 - 1 - 35



10-10

5 W (dB)

10-9

10 15 20 25

10-8

10-7

10-6

10-5

10-4

10-3

10-2

16QAM 16PSK

2PSK4PSK

8PSK

32PSK

64QAM




3 - 1 - 36



Comparison of different modulation schemes(Theoretical W and S/N values at 10-6 BER; calculated values may have slightly different assumptions)a) Basic modulation scheme

(1) As an example, errorcorrection with redundancy (r)of 6.7% is used for calculationin this Table.

System Variants W(dB)

S/N(dB)

NyquistBandwidth (bn)

FSK 2-state FSK with discriminator detection 13.4 13.4 B3-state FSK (duo-binary) 15.9 15.9 B4-state FSK 20.1 23.1 B/2

PSK 2-state PSK with coherent detection 10.5 10.5 B4-state PSK with coherent detection 10.5 13.5 B/28-state PSK with coherent detection 14.0 18.8 B/316-state PSK with coherent detection 18.4 24.4 B/4

QAM 16-QAM with coherent detection 17.0 20.5 B/432-QAM with coherent detection 18.9 23.5 B/564-QAM with coherent detection 22.5 26.5 B/6128-QAM with coherent detection 24.3 29.5 B/7256-QAM with coherent detection 27.8 32.6 B/8512-QAM with coherent detection 28.9 35.5 B/9

Basic modulation schemes with FECQAM 16-QAM with coherent detection 13.9 17.6 B/4*(1+r)with 32-QAM with coherent detection 15.6 20.6 B/5*(1+r)

block 64-QAM with coherent detection 19.4 23.8 B/6*(1+r)codes (1) 128-QAM with coherent detection 21.1 26.7 B/7*(1+r)

256-QAM with coherent detection 24.7 29.8 B/8*(1+r)512-QAM with coherent detection 25.8 23.4 B/9*(1+r)




3 - 1 - 37


Comparison of Different Mod. Schemes

B) Coded modulation scheme

System Variants W(dB)

S/N(dB)

NyquistBandwidth (bn) (1)

BCM (2) 16 BCM - 8D (QAM. One step partition) 15.3 18.5 B/3.7580 BCM - 8D (QAM. One step partition) 23.5 28.4 B/688 BCM - 6D (QAM. One step partition) 23.8 28.8 B/696 BCM - 4D (QAM. One step partition) 24.4 29.0 B/6128 BCM - 8D (QAM. One step partition) 23.6 28.2 B/6

TCM (3) 16 TCM - 2D 12.1 14.3 B/332 TCM - 2D 13.9 17.6 B/464 TCM - 4D 18.3 21.9 B/5.5128 TCM - 2D 19.0 23.6 B/6128 TCM - 4D 20.0 24.9 B/6.5512 TCM - 2D 23.8 29.8 B/8512 TCM - 4D 24.8 31.1 B/8.5

MLCM (4) 32-MLCM - 2D (QAM) 14.1 18.3 B/4.564-MLCM - 2D (QAM) 18.1 21.7 B/5.5128-MLCM - 2D (QAM) 19.6 24.5 B/6.5

(1) The bit rate B does not include code redundancy.(2) The block code length is half the number of the BCM signal dimensions.(3) The performances depend upon the implemented decoding algorithm.

In this example, an optimum number is used.(4) In this example, convolutional code is used for lower 2 levels and block codes are used for the third level to

give overall redundancies as those of 4D-TCM. Specially redundancies on the two convolutional codedlevels are 3/2, 8/7 and 24/23 on the block coded third level.




3 - 1 - 38


Roll-off calculation example [cont.]

Example 1Available bandwidth = 40 MHzTransmitted stream = 34 Mbit/sModulation type = 2 PSKRoll-off = ?

BW = fb (1+α)40 = 34 (1+ α)a = 40/34-1 = 0.05

RELATIONSHIP BETWEEN fb and fs AS FUNCTION OF THE MODULATION TYPE

2 PSK fs = fb fb = 34 Mbit/s fs = 34 MHz4 PSK fs = fb/2 fb = 34 Mbit/s fs = 17 MHz8 PSK fs = fb/3 fb = 34 Mbit/s fs = 11.3 MHz16 QAM fs = fb/4 fb = 34 Mbit/s fs = 8.5 MHz




3 - 1 - 39


Roll-off calculation example

Example 2Available bandwidth = 20 MHzTransmitted stream = 140 Mbit/sModulation type = ?

BW = fb/nn = fb/BW = 140/20 = 7

27 = 128 128 QAM with α = 028 = 256 256 QAM with α = 1




3 - 1 - 40

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3 - 1 - 41

2 Equipment unavailability




3 - 1 - 42


Introduction [cont.]

Unavailability = Part of the time in which the link is out of order.

Where:

MTTR = Mean Time To Repair

MTBF = Mean Time Between Failures

MTBFMTTRMTTRU

+=

Equipment unavailability




3 - 1 - 43


Introduction

By supposing:

Failures statistically independent

MTTR << MTBF

UNAVAILABILITY OF SERIES BLOCKS

U1-2 = UA + UB

UNAVAILABILITY OF PARALLEL BLOCKS

U1-2 = UA • UB

A B1 2

1 2

A

B




3 - 1 - 44


Unavailability objective

EQUIPMENT UNAVAILABILITY OBJECTIVE

for HRDP (L = 2500 km) is supposed to be 1/3 of the total unavailability:

Ueq. < 0.1% = 0.001

The HRDP consists of 9 switching sections (section length = 280 km approx.)

For one-direction of the link only:

Ueq.s1 < 55.10-6

4eq.eq.s 101.1

9U

U −•≤=




3 - 1 - 45


Unavailability of a non-protected section (1+0) [cont.]

Suppose that a radio section consists of:

1 Tx Terminal

1 Rx Terminal

5 Repeaters (equal each other)




3 - 1 - 46


Unavailability of a non-protected section (1+0) [cont.]

1+0 radio section: 6 hops, 5 repeater stations

Mod. Tx

PSU

Z'Rx Dem

PSU

Mod Tx Rx Dem

PSU

Z

L = 50 km L = 50 km




3 - 1 - 47


Unavailability of a non-protected section (1+0)

UTx Term.= UTerm. Mod + UTx + UPSU

URep. = URx + URep. Dem + URep. Mod + UTx + UPSU

URx Term. = URx + UTerm. Dem + UPSU

Unavailability of the non-protected section (uni-directional) (points Z-Z’):

US(1+0) = UTx Term + 5 • URep. + URx Term




3 - 1 - 48


Unavailability of a protected section (1+1) [cont.]

TS = Tx part of the switching system, the failure of which causes the total unavailability of the section.

RS = Rx part of the switching system, the failure of which causes the total unavailability of the section.

Lp = Part of the switching system, the failure of which doesn’t allow the regular operation of the switching system.

MTBFs = Global MTBF of the switching system “series” part.

MTBFp = Global MTBF of the switching system “parallel” part.

US

US

R'TS

RRS

Lp




3 - 1 - 49


Unavailability of a protected section (1+1) [cont.]

1+1 radio section: 6 hops, 5 repeater stations

Mod. Tx

PSU

Z'Rx Dem

PSU

Mod Tx Rx Dem

PSU

Z

L = 50 km L = 50 km

Mod. Tx

PSU

Z'Rx Dem

PSU

Mod Tx Rx Dem

PSU

Z

R' R

LOGIC




3 - 1 - 50


Unavailability of a protected section (1+1)

Global unavailability of the 1+1 protected section:

The section is unavailable due to:

failures of the 2 channels

failure of the “series” part of the switching system

failure of a channel and of the “parallel” part of the switchingsystem

( ) ( ) ( ) ( )0.5ηUUηUUU 01sparser2

01s11s ≅++= +++ •




3 - 1 - 51

3 M.21xx-series Recommendations




3 - 1 - 52


General concepts [cont.]

Differences between Recommendations G.821/G.826 and the M.21xx series start with their different origins:

G-series Recommendations are from ITU-T Study Group 13 (General networkissues);

M-series are from Study Group 4 (Network Maintenance and TMN).

Main differences:

G.821/G.826 define long-term performance objectives to be met.

G.821/G.826 require very long test intervals (one month).

The M-series Recommendations are particularly useful when bringing-into-service new transmission equipment. They are intended to assure that the requirements of the G series are met in every case.

As a general rule, the requirements of the M-series are tougher than those of the G-series.

For practical reasons, the M.21xx-series Recommendations allow short test intervals.




3 - 1 - 53


General concepts [cont.]

Media independent (ITU-T)

M.2100 for PDH paths sections and transmission systems

M.2110 how to apply M.2100 and M.2101 for BIS (Bring-Into-Service)

M.2120 how to apply M.2100 and M.2101 for maintenance

M.2101 for SDH paths and multiplex section

Radio specific (ITU-R)

F.1330 for parts of international PDH and SDH paths and sections.




3 - 1 - 54

End of Module

Radio Network Planning

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