Transmission Planning MOD 2

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

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1.2 Network Planning Method3FL 42104 AAAA WBZZA Edition 2 - July 2005

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

Switch to notes view! Page

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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Table of Contents [cont.]

Switch to notes view! Page

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 Absorption� Refraction through the atmosphere: Ray Curvature� Refraction through the atmosphere: Multipath Propagation.

Rain:� Raindrop Absorption� Raindrop Scattering� RF Signal Depolarization.

Ground:� Diffraction through Obstacles� Reflections.




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1 Power budget

Radio Link Equation [cont.]

GTx GRxAfsl

Aa

ABRTx

AfTx

PTx

ABRRx

AfRx

PRx




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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




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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

Antenn

aGain

[dB]

030

Frequency [GHz]5 10 15 20

34

38

42

46

50

0.5m

1m

2m3m

4m

65.055.0 −== efficiencyAntennaη




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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




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1 Power budget

Exercise

Exercise 1 - Power budget Calculate the power budget of the following link

operating at 6 GHz (Margin = 1 dB).

2 m 36 km

Aa = negligable

ABRTx= 0.5 dB

(EW64)

200 m

PTx = +30 dBm

2 m

(EW64)

200 m

ABRRx= 0.5 dBPRx = ?




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1 Power budget

Exercise

Exercise 2 - Antenna gain calculationCalculate the gains of the antennas to be used inthe following link:� PTx : +30 dBm� PRx : -36 dBm� Frequency : 6 GHz� Distance : 48 km� Losses of branching filters and

feeder in station 1 : 1.5 dB� Losses of branching filters and

feeder in station 2 : 2.5 dB




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Blank Page





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2 Effects of atmosphere




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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.




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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 law dictates that the ray will be bent away from the normal and back towards 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.




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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




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Atmosphere layered structure

Earthn1

n2

n3

n4

n5

Etc.




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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 =




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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.




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(a) N profile

Super-refraction

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.




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Causes of anomalous propagation

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.




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Anomalous propagation

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.




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Exercise

Why does not the electromagnetic wave travel in a straight line?� due to the gravity of the earth� due to the refractive gradient of the atmosphere� due to the magnetic field of the earth

What does it mean standard atmosphere?




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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




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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




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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 +

=




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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).




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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

KN

OT

EX

CE

ED

ED

FO

R0.

01%

OF

TIM

E




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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)


Attenuation by atmosphere gases [cont.]




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Attenuation by atmosphere gases




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Exercise

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

Exercise 2 - Rain unavailabilityCalculate the rain unavailability in the following link:� Region : L� Distance : 50 km� Frequency : 11 GHz� Polarization : H� Fade Margin : 30 dB




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3 Diffraction




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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




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3 Diffraction

Diffraction

Tx Rx

Activatedfictitioussources

Non-activatedfictitioussources




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3 Diffraction

Exercise

Exercise - 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%).




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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

+

-

+




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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 −=




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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




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3 Diffraction

Exercise

Exercise - 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).




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3 Diffraction

Obstruction loss

Diffractionloss relative to 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 paths

B : theoretical knife-edge loss curve

D : theoretical smooth spherical Earth loss curve at 6.5 GHz and k=4/3

Ad : empirical diffraction loss for intermediate terrain

h : amount by which the radio path clears the Earth’s surface (m)

F1 : radius of the first Fresnel zone (m)




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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




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4 Equipment parameters related to propagation




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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




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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 - 52



Example 1: Calculation of PRX threshold using different modulation types

fb = 140 Mbit/s

RF = 6 GHz

T =+25°C

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

(22 = 4)

18.7

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

(24 = 16)

15.5

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

(26 = 64)

13.3

10 log F = 4 dB

PRx (Th) = ?

ModulationType

4 PSK

16 QAM

64 QAM




1 - 2 - 53



Example 2: 10-3 receiver threshold calculation

Input dataF (dB) 2.50

BIT RATE (MHz) 155.52MOD. (nQAM) 128 7 levels

REDUNDANCY 1.06S/N MODEM (dB) 26.00

SYMB. RATE (MHz) 23.5

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

THRESHOLD -71.78memo

KTB -100.53 KT (dB) -114

KTBF -98.03 THERMAL NOISE




1 - 2 - 54


PRx Threshold General Formula

FM = PRX(NOM) - PRX(Th)

FM = Fading Margin

hop (Km)

PTX PRX(NOM)

PRX(NOM) = PRX(Th) + FM




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Exercise

Exercise 1 - Roll-off factor

Calculate the roll-off factor with the following data:� Available bandwidth : 30 MHz� Digital signal : STM1

(155.520 Mbit/s)� Modulation type : 128 QAM� Redundancy : 10%




1 - 2 - 56


Exercise

Exercise 2 - PRx threshold

Calculate the 10-6 BER PRx threshold in the following system:� Digital signal : STM1� Modulation 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.




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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 - ∆ 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 + ∆ 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

10pAFMAsettingBy




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%of

Tim

e

Attenuation [dB]

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




1 - 2 - 71

6 Propagation model




1 - 2 - 72

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 - 73

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

FADING

ACTIVITY




1 - 2 - 74

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 - 75

6 Propagation model

Exercise

Which is the cause of the multipath fading?� Rain� Layers in the atmosphere




1 - 2 - 76

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

>FM

Curve for P0 = 110 dB/dec




1 - 2 - 77

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 - 78

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 - 79

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 : 30 dB� Hop length : 50 km� Type of hop : flat� Frequency : 8 GHz� Roughness (S) : 15




1 - 2 - 80

6 Propagation model

Selective fading outage [cont.]

The reflected ray is characterized by:� amplitude� delay� phase 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 a2

The 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 - 81

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 - 82

6 Propagation model


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




1 - 2 - 83

6 Propagation model


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

Selective fading outage

where:

∆fo = 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]

( )2m2

s

n τTKη4.3Ps ×

××=

( )75.002.0exp1 P×−−=η

2010cB

r

sosn

TfTK−

∆=τ

[ ]nsdm

3.1

507.0

=τ




1 - 2 - 84

6 Propagation model

Selective fading outage

Signature

Bc




1 - 2 - 85

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 : STM1� Modulation type : 128 QAM� Redundancy : 10%� Kn : 0.25




1 - 2 - 86

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 - 87

7 Quality objectives of Digital Radio Links




1 - 2 - 88


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 - 89


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




1 - 2 - 90


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 - 91


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 - 92


ITU-T G.821 [cont.]

ITU 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 Grade

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

� Medium Grade

Systems operating between local exchanges in the national network.

� Local Grade

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




1 - 2 - 93


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 - 94

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 - 95


ITU-T G.821 [cont.]

High grade Medium grade Local grade

HDRP Rec. 594PerformanceObjectives Rec. 697

Real link Rec. 634

Rec. 696

HDRP Rec. 557AvailabilityObjectives Rec. 1053

Real link Rec. 695

G.821 related specs




1 - 2 - 96


ITU-T G.821 [cont.]

ITU-R Rec. 557

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

•Unavailability < 0.3 %




1 - 2 - 97


ITU-T G.821 [cont.]

ITU-R Rec. 695

� Unavailability objective for high grade real link:

•Unavailability ( )2500kmL%2500

Lx0.3 ≤<




1 - 2 - 98


ITU-T G.821 [cont.]

ITU-R Rec. 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 - 99

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 - 100


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

H.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 - 101


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.




1 - 2 - 102



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




1 - 2 - 103



G.826-8 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




1 - 2 - 104



� 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 SES




1 - 2 - 105



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

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 - 106



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




1 - 2 - 107

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.826-8 Basic apportionment principles




1 - 2 - 108

1%

Objectivesallocation

17.5%

PEP

Terminatingcountry

27500 Km

Nationalportion

NationalportionInternational portion

10% 17.5%

2% 2% 2% 2% 1%

PEP

45%

Transitcountries

Terminatingcountry



G.826-8 Country based apportionment




1 - 2 - 109



G.826-8 - 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 - 110

International Nationalportion portion

HDRP Rec. F.1092 Rec. F.1189PerformanceObjectives

Real link Rec. F.1397 Rec. F.1491

HDRP --- ---AvailabilityObjectives

Real link as G.821 as G.821


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

G.826/8 related recommendations




1 - 2 - 111


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

Error Performance Objectives for constant bit rate digital path at or above the primary rate carried by DRRS which may form part of the 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 - 112


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

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 - 113



� EPO (Error Performance Objectives) for real digital radio links used in the international portion of 27500 km HRP at or above the primary rate

� 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 - 114

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 - 115



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 - 116



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 - 117



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 - 118



Error Performance Objectives for constant bit rate digital path at or above the primary rate carried by DRRS which may form part or all of the 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 - 119



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 - 120



Error performance objectives for real digital radio links used in the national portion of a 27500 km HRP at or above the primary rate.

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 - 121



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 - 122


Exercise

Exercise 1 - Unavailability due to the propagationCalculate the unavailability 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 km� Type of country : intermediate country� Block Allowance Ratio : 1




1 - 2 - 123

8 Fading countermeasures




1 - 2 - 124


Adopted techniques

Techniques adopted to reduce the multipath fading impairment:� Adaptive Signal Equalization at the Receiver� Diversity Reception:

• Space Diversity• Frequency Diversity• Angle Diversity




1 - 2 - 125


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 - 126


Adaptive equalization [cont.]

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

Without Equalizer

With EqualizerN

otch

Dep

th[d

B]




1 - 2 - 127


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 algorithm� BB switch and IF combiner

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

� single channel performance� correlation between the bearers� multipath fading probability




1 - 2 - 128



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 - 129



a) Frequency diversity

∆F = 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 τ∆F0.9-expK ••=

−= ••

−2

62s λ

S104expK

2f

2s

2fs KKK •=

2f

2s2

2s1

2fs KKKK ••=

1.3

50d0.7




1 - 2 - 130



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 - 131


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 - 132


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 equipment failure. 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




1 - 2 - 133


Exercise

Exercise - Frequency diversity improvement

Calculate the frequency diversity improvement by using the following data:� Frequency : 8 GHz� Hop lenght : 50 km� Frequency diversity : 40 MHz� Multipath occurrence factor Po : 1� Outage probability without protection (10-3) : 0.0001




1 - 2 - 134


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 - 135


Exercise

Exercise - Space diversity improvement

Calculate the space diversity improvement by using the following data:� Vertical antenna separation : 8 m� Frequency : 8 GHz

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




1 - 2 - 136


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 - 137


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

F1DEM

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




1 - 2 - 138


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 with

different 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 - 139

9 Reflections from ground




1 - 2 - 140


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 periods� Enhancement 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 - 141


Geometrical model

Tx

PR1 R2

D1

2α

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 - 142


Rx signal with reflection

In the presence of reflection, the overall received signal (S) is given by the (vectorial) additionof 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 l; 360 deg. phase shift for each l)• 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 level

Direct 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 - 143


Rx signal level

Rx Level

TxRx




1 - 2 - 144


Exercise

Why does the reflected ray from the ground change?




1 - 2 - 145


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 ray

� Clearance:• For the Lower Antenna, in most cases, Clearance= 0 is enough;

• Usual rules for the Higher Antenna.

Implementation Options:

� BB Switching to the best signal� IF Adaptive Combining (as for Multipath countermeasure)

� RF Combining (Anti-Reflection System).




1 - 2 - 146


Exercise

In the space diversity configuration is the antenna separation vertical or horizontal?




1 - 2 - 147

10 Frequency re-use




1 - 2 - 148

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 - 149

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 usingthe 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 - 150

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 - 151

10 Frequency re-use

Exercise

What is the difference between XPD and XPI?




1 - 2 - 152

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 - 153

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 - 154

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 - 155

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

OUT

DATAIN

DATA

LO

H

V

V

H

H H

V V

V

H




1 - 2 - 156

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

EXAMPLE: 1 dB WORSENING DUE TO C/I

MODULATION C/N E-3 C/IdB dB

mod 128 cross 23 30

MODULATION C/N E-3 Rx THRESHOLDdB dBm

mod 128 cross 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

10 Frequency re-use

Same frequency re-used channel (cross-polar)




1 - 2 - 157

10 Frequency re-use

Exercise

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




1 - 2 - 158

10 Frequency re-use

Adjacent frequency re-used channel (co-polar)

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

EXAMPLE: 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 -27.00 -55.00




1 - 2 - 159

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 - 160

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-exp0.3 -1




1 - 2 - 161

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

10PP •=

IC-QXPD o

0 +

IC-XPIRF QXPD o

0 ++

IC-NFDQXPD o

0 ++

ICo




1 - 2 - 162

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 - 163

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 - 164

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/Alog 23.26

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

( )2nXPR 10P −=




1 - 2 - 165

11 Interferences




1 - 2 - 166

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 - 167

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 - 168

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 EASTINTERFERENCE

TX TO RX

PTx1 PRx2ANTENNA 1 ANTENNA 2

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

TX1 RX2




1 - 2 - 169

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 10̂ -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 - 170

11 Interferences

Signals 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 - 171

11 Interferences

Signals 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 10 -̂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 - 172

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 interference

ACTIVITY Type "D"

B A

C

w

I




1 - 2 - 173

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




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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 =




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End of Module

Transmission Planning MOD 2

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