Transmission Planning Mod 2

Network Planning 1.2 Network Planning Method

3FL 42104 AAAA WBZZA Edition 2 - July 2005

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1-2-2

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Objectives Network Planning - Network Planning Method

1-2-

3

“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 power threshold. “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 Network Planning - Network Planning Method

1-2-

4

“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 Network Planning - Network Planning Method

1-2-

5

Page

Switch to notes view! 1 Power budget L.O.S. (Line Of Sight) Radio Links Main Propagation Phenomema Radio Link Equation Free Space Loss Antenna Gain Losses Exercise Exercise Blank Page 2 Effects of atmosphere Fixed terrestrial microwave link propagation Refraction through the atmosphere Anomalous propagation Exercise K-factor Variability of the K-factor Attenuation by atmosphere gases Exercise 3 Diffraction Diffraction Exercise Fresnel zones First Fresnel zone radius Exercise - RADIO NETWORK PLANNING Obstruction loss Clearance rules 4 Equipment parameters related to propagation PRx Threshold General Formula Exercise Exercise Signature measurement Blank Page 5 Propagation during rain Propagation during rain Attenuation by rain Rain Unavailability Prediction 6 Propagation model Fade margin Fading definitions Exercise Flat fading outage Exercise Selective fading outage Exercise Single channel global outage 7 Quality objectives of Digital Radio Links Introduction ITU-T recommendations Error Performance Events Impact of propagation on performance objectives ITU-T G.821 Rec. ITU-T G.826 and G.828 Rec. ITU-T G.826 and G.828 - ITU-R F.1092 Rec. ITU-T G.826 and G.828 - ITU-R F.1397

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7 8 9 11 12 13 15 16 17 18 19 20 24 29 30 32 35 37 38 39 41 42 43 45 46 All rights reserved © 2005, Alcatel 47 48 49 54 55 56 59 60 61 63 69 70 71 73 74 75 78 79 84 85 86 87 88 89 90 91 100 110 112 117

Table of Contents [cont.] Network Planning - Network Planning Method

1-2-

6

Page

Switch to notes view! Rec. ITU-T G.826 and G.828 - ITU-R F.1189 Rec. ITU-T G.826 and G.828 - ITU-R F.1491 Exercise 8 Fading countermeasures Adopted techniques Diversity Improvement Frequency diversity Exercise Space diversity Exercise Space and frequency diversity Angle diversity 9 Reflections from ground Reflections from ground Geometrical model Rx signal with reflection Rx signal level Exercise Space diversity in reflection paths Exercise 10 Frequency re-use Introduction Terminology Exercise Concepts - RADIO NETWORK PLANNING Interferences Interference types Frequency reuse system block diagram Same frequency re-used channel (cross-polar) Exercise Adjacent frequency re-used channel (co-polar) Prediction of outage due to multipath propagation Prediction of outage due to rain effects 11 Interferences Introduction Modem performances Local sources Signals belonging to the same system at a common location Signals belonging to the same system from other locations Signals belonging to the same system from other locations through an overreach condition Exercise Blank Page End of Module

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1-2-7

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1 Power budget

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1 Power budget

L.O.S. (Line Of Sight) Radio Links 1-2-8

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Site A

Site B

Propagation

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

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1 Power budget

Main Propagation Phenomema 1-2-9

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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.] 1 - 2 - 10

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GTx

Afsl

GRx AfRx

AfTx Aa

ABRRx

ABRTx PTx

PRx

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1 Power budget

Radio Link Equation 1 - 2 - 11

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

: : : : : : : : : : :

received power transmitted power propagation free-space loss atmospheric absorption loss transmit antenna gain receive antenna gain loss in the transmit feeder loss in the receive feeder loss in the RF branching (filters) system other attenuations (mirrors, back-to-back antennas, attenuators) Margin (tolerance)

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[dBm] [dBm] [dB] [dB] [dB] [dB] [dB] [dB] [dB] [dB] [dB]

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1 Power budget

Free Space Loss 1 - 2 - 12

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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 doubled or the frequency is doubled.

150

140

Att. [dB]

130

120

110 4

8

12

16

20

24

28

32

36

40

44

48

Distance [km] 2 GHz 4 GHz 6 GHz 7 GHz 10 GHz 15 GHz

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1 Power budget

Antenna Gain 1 - 2 - 13

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

G=

In dB units:

2

= Antenna efficiency = 0.55 0.65 (depending on )

G = 20 log( D ) + 20 log( F ) + 18.2 ± 0.5

50

Antenna gain is 6 dB higher if: - antenna diameter is doubled, for a given frequency - frequency is doubled, for a given diameter.

4m 3m

46

2m Antenn 42

1m

aGain [dB]

38

0.5m

34

30 0

5

10

15

20

Frequency [GHz] - RADIO NETWORK PLANNING

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1 Power budget

Losses [cont.] 1 - 2 - 14

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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).

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1 Power budget

Losses

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1 - 2 - 15

Waveguide Attenuation

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1 Power budget

Exercise 1 - 2 - 16

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Exercise 1 - Power budget Calculate the power budget of the following link operating at 6 GHz (Margin = 1 dB). 2m

(EW64)

36 km

2m

Aa = negligable

200 m

(EW64) 200 m

ABRTx= 0.5 dB

ABRRx= 0.5 dB

PRx = ?

PTx = +30 dBm

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1 Power budget

Exercise Network Planning - Network Planning Method

1 - 2 - 17

Exercise 2 - Antenna gain calculation Calculate the gains of the antennas to be used in the 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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1 - 2 - 19

Network Planning - Network Planning Method

2 Effects of atmosphere

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2 Effects of atmosphere

Fixed terrestrial microwave link propagation 1 - 2 - 20

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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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2 Effects of atmosphere

Refraction through the atmosphere [cont.] Network Planning - Network Planning Method

1 - 2 - 21

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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2 Effects of atmosphere

Refraction through the atmosphere [cont.] 1 - 2 - 22

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Snell’s Law

n= where:

c v c = velocity of light (vacuum) v = velocity of light (medium)

v=

1 (µ

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) n2 2

1

n1

n1 > n 2 n 2 × cos% 2 = n1 × cos%1

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.

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2 Effects of atmosphere

Refraction through the atmosphere [cont.] 1 - 2 - 23

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. Etc n5 n4 n3 n2 n1

Earth Atmosphere layered structure

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2 Effects of atmosphere

Refraction through the atmosphere 1 - 2 - 24

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

N = (n 1)×106 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”).

N = 77.6 × where:

e P + 3.73 × 105 × 2 = dry term + wet term T T

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

G=

dN dh

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 - RADIO NETWORK PLANNING

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2 Effects of atmosphere

Anomalous propagation [cont.] 1 - 2 - 25

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Standard Conditions

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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.

3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 25

2 Effects of atmosphere

Anomalous propagation [cont.] 1 - 2 - 26

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negative N dh

N =0 dh positive N dh

positive 0

h negative

Standard

Standard

N (a) N profile

(b) Off boresight path profile and reduced clearance

Sub-refraction

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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.

3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 26

2 Effects of atmosphere

Anomalous propagation [cont.] 1 - 2 - 27

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(a) N profile

Super-refraction

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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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2 Effects of atmosphere

Anomalous propagation [cont.] Network Planning - Network Planning Method

1 - 2 - 28

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: Evaporation A 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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2 Effects of atmosphere

Anomalous propagation 1 - 2 - 29

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Nocturnal Radiation The 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 Inversion Under 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. Advection In coastal regions a relatively warm air flow across a cooler sea will cause a temperature inversion and form a surface based duct. Weather Fronts Cool dense air may force less dense warmer air above it, causing a temperature inversion and a raised duct. - RADIO NETWORK PLANNING

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2 Effects of atmosphere

Exercise

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1 - 2 - 30

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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2 Effects of atmosphere

K-factor [cont.] 1 - 2 - 31

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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.

R eq = KR o

1 = 1

R o = 6370 km ;

dn = 10 6 G dh

where G =

1 1 = R eq R o

1 1

1 1 = KRo Ro

1 1 = + 10 6 G 1 Ro

KRo

1 + 10 6 G = 1 Ro

1 = 157 • 10 Ro

6

dN dh Ro

K=

where G is expressed in N - units/km

157 157+ G

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2 Effects of atmosphere

K-factor

1 - 2 - 32

Network Planning - Network Planning Method KR0

R RAY

T

R T

B (x) RAY

H (x)

h

E (x)

h

EQUIVALENT EARTH

h2 h1

E (x)

B (x)

FLAT EARTH

T'

R' x

T'

d-x

R' x'

d-x

RAY KR R

BR (x) T E (x)

h2 H (x)

h1

REAL CASE BE (x)

T'

R' x

d-x

R0

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2 Effects of atmosphere

Variability of the K-factor [cont.] 1 - 2 - 33

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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. K min =

157 (157 + G e (0.01% ))

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2 Effects of atmosphere

Variability of the K-factor [cont.] Network Planning - Network Planning Method

1 - 2 - 34

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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2 Effects of atmosphere

Variability of the K-factor 1 - 2 - 35

Network Planning - Network Planning Method 1.4

K NOT EXCEEDED FOR 0.01% OF TIME

1.2

b 1

0.8

a

0.6

c 0.4

0.2

10

20

40

60

80

100

200

PATH LENGTH, Km

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2 Effects of atmosphere

Attenuation by atmosphere gases [cont.] 1 - 2 - 36

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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)

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2 Effects of atmosphere

Attenuation by atmosphere gases Network Planning - Network Planning Method

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1 - 2 - 37

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2 Effects of atmosphere

Exercise

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1 - 2 - 38

Exercise 1 - Atmosphere gas attenuation Calculate the attenuation due to the atmosphere gases in a 20 km link at 20 GHz. Exercise 2 - Rain unavailability Calculate 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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1 - 2 - 39

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3 Diffraction

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3 Diffraction

Diffraction [cont.] 1 - 2 - 40

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

A

B

a1

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.

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b1

a2

b2

a3

b3

a4

b4

a5

b5

t0

t0 + dt

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3 Diffraction

Diffraction 1 - 2 - 41

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Activated fictitious sources

Rx

Tx

Non-activated fictitious sources

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3 Diffraction

Exercise Network Planning - Network Planning Method

1 - 2 - 42

Exercise - Antenna heigths Calculate 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 1 - 2 - 43

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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 = n;/2 and phase shift of nU is an ellipsoid with radius F1.

TxP + PRx = TxRx + n Tx

7 2

where n = 1, 2.... Rx

D P

1st Fresnel (D + /2) 2nd Fresnel (D + )

a) Side View

3rd Fresnel (D + 3 /2)

+ 1st Fresnel (D + /2)

b) Cross Section

- 2nd Fresnel (D + ) + 3rd Fresnel (D + 3 /2)

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3 Diffraction

First Fresnel zone radius [cont.] 1 - 2 - 44

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

F1 =

300 D1(D D1) (F D )

(m )

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.

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3 Diffraction

First Fresnel zone radius 1 - 2 - 45

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

60 50 2 GHz

40 Fresnel Radius [m]

4 GHz

30

7 GHz 12 GHz

20 10 0

0

20

40

60

80

100

D=Hop Length [km] - RADIO NETWORK PLANNING

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3 Diffraction

Exercise Network Planning - Network Planning Method

1 - 2 - 46

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 1 - 2 - 47

Network Planning - Network Planning Method

-10 0 10 Diffraction loss relative to free space 20 (dB)

B Ad

D

30 40 -1.5

-1

-0.5

0

0.5

1

Normalized clearance h/F1

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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)

3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 47

3 Diffraction

Clearance rules 1 - 2 - 48

Network Planning - Network Planning Method

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 conditions 2. 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 = 4/3 2. clearance be 0.6 or greater at the minimum K related to the climatic region and the path length considered

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Network Planning - Network Planning Method

1 - 2 - 49

4 Equipment parameters related to propagation

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4 Equipment parameters related to propagation

PRx Threshold General Formula [cont.] 1 - 2 - 50

Network Planning - Network Planning Method

F Low Noise

RX

PRX (Th) N

Demodulator

PRX(Th) NF

S N

10

-6

Error Detector

F

=

10-3

S input N S output N

E quipment parameters related to propagation F = 1 F > 1 PRX(Th) S = NF N

Theoretical Pratical

10-6

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4 Equipment parameters related to propagation

PRx Threshold General Formula [cont.] 1 - 2 - 51

Network Planning - Network Planning Method

In dB

PRx (Th) =

S + 10 log F + 10 log N N 10-6 N = KTB K = Boltzman constant T =Temperature B = Bandwidth 10 log N=10 log KT + 10 log B if T = +25C°

10 log KT= - 114 dB DEPENDS ON THE

Modulation Type

PRx (Th) =

RF Amplifier

10 log N=10 log B - 114 dB

Modulation Type

S + 10 log F + 10 log B - 114 dB N 10-6

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4 Equipment parameters related to propagation

PRx Threshold General Formula [cont.] 1 - 2 - 52

Network Planning - Network Planning Method

Example 1: Calculation of PRX threshold using different modulation types fb = 140 Mbit/s 10 log F = 4 dB

RF = 6 GHz T =+25°C

P Rx (Th) = ?

4 PSK Modulation Type

16 QAM 64 QAM

18.7 4 PSK

P Rx (Th) +13.5 = + 4 + 10 log 140 - 114 = -78.1 dBm (22 = 4) 2 15.5

16 QAM

P Rx (Th) +20.5 = + 4 + 10 log 140 - 114 = -74.1 dBm (24 = 16) 4 13.3

64 QAM

P Rx (Th) +26.5 = + 4 + 10 log 140 - 114 = -70.2 dBm (26 = 64) 6

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4 Equipment parameters related to propagation

PRx Threshold General Formula [cont.] 1 - 2 - 53

Network Planning - Network Planning Method

Example 2: 10-3 receiver threshold calculation

Input data F (dB) BIT RATE (MHz) MOD. (nQAM) REDUNDANCY S/N MODEM (dB) SYMB. RATE (MHz)

2.50 155.52 128 1.06 26.00 23.5

7

levels

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

-71.78

KTB

-100.53

KTBF

memo KT (dB)

-114

-98.03 THERMAL NOISE

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4 Equipment parameters related to propagation

PRx Threshold General Formula 1 - 2 - 54

Network Planning - Network Planning Method

PTX

PRX(NOM)

FM = Fading Margin hop (Km) FM = PRX(NOM) - PRX(Th)

PRX(NOM) = PRX(Th) + FM

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4 Equipment parameters related to propagation

Exercise

1 - 2 - 55

Network Planning - Network Planning Method

Exercise 1 - Roll-off factor Calculate the roll-off factor with the following data: Available bandwidth Digital signal Modulation type Redundancy

: 30 MHz : STM1 (155.520 Mbit/s) : 128 QAM : 10%

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4 Equipment parameters related to propagation

Exercise

1 - 2 - 56

Network Planning - Network Planning Method

Exercise 2 - PRx threshold Calculate the 10-6 BER PRx threshold in the following system: Digital signal Modulation type Redundancy Noise figure

: : : :

STM1 128 QAM (S/N at 10-6=26.7 dB) 6.7% 4 dB

Note: Use the Nyquist bandwidth.

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4 Equipment parameters related to propagation

Signature measurement [cont.] 1 - 2 - 57

Network Planning - Network Planning Method

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]

BER < 10-3

BER > 10-3

-15 -10 -5

0

5

10 15

Relative Notch Position [MHz] - RADIO NETWORK PLANNING

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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 a measure of the receiver sensitivity to multipath distortions.

3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 57

4 Equipment parameters related to propagation

Signature measurement [cont.] 1 - 2 - 58

Network Planning - Network Planning Method

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: Amplitude = 1

+

Y

Tx

Delay

MOD

Phase

= echo signal delay

Rx

= echo signal phase shift (relative to the direct signal)

Att

b

DEM

b = echo signal amplitude

Pattern generator

Error detector

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4 Equipment parameters related to propagation

Signature measurement

1 - 2 - 59

Network Planning - Network Planning Method

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 - H 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 given threshold (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. Notch Frequency plane.

e)

Move the Notch Frequency fo of a given frequency step. Repeat steps c), and d) until fo = Fc + H 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).

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 60

1 - 2 - 60

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1 - 2 - 61

Network Planning - Network Planning Method

5 Propagation during rain

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5 Propagation during rain

Propagation during rain [cont.] 1 - 2 - 62

Network Planning - Network Planning Method

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.

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5 Propagation during rain

Propagation during rain 1 - 2 - 63

Network Planning - Network Planning Method

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 crosspolar 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). - RADIO NETWORK PLANNING

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 63

5 Propagation during rain

Attenuation by rain [cont.] 1 - 2 - 64

Network Planning - Network Planning Method

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 an integration time of 1 min). If this information is not available from local sources of long-term measurements it is possible to refer to the following table (Rec. ITU-R P.837).

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5 Propagation during rain

Attenuation by rain [cont.] 1 - 2 - 65

Network Planning - Network Planning Method

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

Percentage of time (%)

A

B

C

D

E

F

G

H

J

K

L

M

N

P

Q

1

<0.1 0.5

0.7

2.1

0.6

1.7

3

2

8

1.5

2

4

5

12

24

.3

<0.8

2

2.8

4.5

2.4

4.5

7

4

13

4.2

7

11

15

34

49

.1

<2

3

5

8

6

8

12

10

20

12

15

22

35

65

72

.03

<5

6

9

13

12

15

20

18

28

23

33

40

65

105

96

.01

<8

12

15

19

22

28

30

32

35

42

60

63

95

145 115

.003

14

21

26

29

41

54

45

55

45

70

105

95

140 200 142

.001

22

32

42

42

70

78

65

83

55

100 150 120 180 250 170

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5 Propagation during rain

Attenuation by rain [cont.] Network Planning - Network Planning Method

1 - 2 - 66

Rainfall Regions - Europe, Africa and Asia - RADIO NETWORK PLANNING

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5 Propagation during rain

Attenuation by rain [cont.] 1 - 2 - 67

Network Planning - Network Planning Method

Step 2:

Compute the specific attenuation, R (dB/km) for the frequency, polarization and rain rate according to the relationship

8 R = k R %0.01 and the data (depending on frequency and polarization) enclosed in the following table.

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5 Propagation during rain

Attenuation by rain [cont.] 1 - 2 - 68

Network Planning - Network Planning Method FREQ.

K (H)

K (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

(H)

(V)

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

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5 Propagation during rain

Attenuation by rain 1 - 2 - 69

Network Planning - Network Planning Method

Step 3:

Step 4:

Compute the effective path length deff of the link by multiplying the actual path length “d” by a distance factor “r”. An estimate of this factor is given by: 1 0.015xmin( R 0.01, ,100) r= d 0 = 35e d 1+ d0 An estimate of the path attenuation exceed for 0.01% of the time is given by:

A 0.01 = 8 R d eff = 8 R dr Step 5:

Attenuation exceed for other percentages of time p in the range 0.001% to 1% may be deduced from the following power law:

A(dB) = A 0.01 × 0.12 × p FM By setting A R = A 0.01

p = 10

(0.546 + 0.043log10 p)

-6.348837 1- 1-0.5769566 Log10

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AR 0.12

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5 Propagation during rain

Rain Unavailability Prediction 1 - 2 - 70

Network Planning - Network Planning Method

% of Time

1

From the Time % vs. Rain Attenuation curve, the Unavailability is computed as the time percentage with attenuation greater than Fade Margin.

0.1

In the Figure the Fade Margin is 30dB. Then the Rain Unavailability is about 0.005%. FM

0.01

0.001 0

10

20

30

40

50

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

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1 - 2 - 71

Network Planning - Network Planning Method

6 Propagation model

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6 Propagation model

Fade margin [cont.] 1 - 2 - 72

Network Planning - Network Planning Method

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

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6 Propagation model

Fade margin 1 - 2 - 73

Network Planning - Network Planning Method

The Outage condition is present when the Rx power is below the Rx Threshold Outage probability: P(Outage)= P [pRx < pRx Th] pRx

NORMAL PROPAGATION

FADING FADE MARGIN

ACTIVITY

THRESHOLDpRx Th

OUTAGE ZONE

TIME

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6 Propagation model

Fading definitions 1 - 2 - 74

Network Planning - Network Planning Method

ATMOSFERIC MULTIPATH

FLAT FADING

SELECTIVE FADING

ANALOG

DIGITAL

ANALOG

DIGITAL

THERMAL NOISE

THERMAL NOISE

INTERMODULATION

INTERSYMBOL INTERFERENCE

FADING EXCEEDS MARGIN OVER THRESHOLD

DISTORSION PRODUCES EYE CLOSURE AND LOSS OF SYNC.

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6 Propagation model

Exercise

Network Planning - Network Planning Method

1 - 2 - 75

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

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6 Propagation model

Flat fading outage [cont.] 1 - 2 - 76

Network Planning - Network Planning Method

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

Pf = Prob{A > FM} = P010

1

Curve for P0 = 1 10 dB/dec

Prob A > FM

0.1

FM 10

P0 = Multipath Occurrence

0.01

Factor.

It is a measure of the multipath activity in a radio hop.

0.001

0.0001

0

10

20

30

40

50

FM [dB]

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6 Propagation model

Flat fading outage [cont.] 1 - 2 - 77

Network Planning - Network Planning Method

Occurence Factor “P0” - Alcatel Method P0 may be measured and directly used or evaluated.

f d P0 = 0.2 a b 4 50

3

= 4 • 10 -7 • a • b • f • d 3

(f in GHz; d in km)

where: a is the climatic coefficient b is the roughness factor Typical values of "a" are: a = 2.4 for maritime hops a = 1 for flat hops a = 0.7 for hill hops a = 0.3 for mountain hops

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6 Propagation model

Flat fading outage 1 - 2 - 78

Network Planning - Network Planning Method

According to the path profile the roughness factor is: b=

flat S 15

- 1.3

irregular

6 < S < 42(m )

(“S” is defined in ITU-R Rep. 338-5 Table III). Typical values of ”b" are: b = 0.25 irregular terrain b = 1 medium terrain b = 4 flat terrain

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6 Propagation model

Exercise

Network Planning - Network Planning Method

1 - 2 - 79

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

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6 Propagation model

Selective fading outage [cont.] 1 - 2 - 80

Network Planning - Network Planning Method

SELECTIVE FADING

refracting layer

a1

reflected rays

a2

1

direct ray

The reflected ray is characterized by: amplitude delay phase shift

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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

1

and

2

seconds.

The channel transfer function is:

) = 1ends + a 1ofe the band + athe 2 ephase of the reflected ray a1 will not and Supposing that is very small (at theH 1( w 2 change 1 1 = 2 2) and by setting a2 = ab and 2 = , the three-ray model becomes a two-ray model with j

j

1

± j

2

± j

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

=n

with

n = 0, 1 …. N

and the minimum points are frequency-spaced by

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

fo 3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 80

fc

1 2

6 Propagation model

Selective fading outage [cont.] 1 - 2 - 81

Network Planning - Network Planning Method

2 ray amplitude response

-20 lg H( )

H( ) a(1+b)

15

20

20 lg a

25 20 lg (1-b)

a(1-b)

fc channel bandwidth

(1+b) (1-b)

30

f

f0

20 lg

f

1/

1/

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6 Propagation model

Selective fading outage [cont.] Network Planning - Network Planning Method

1 - 2 - 82

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

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6 Propagation model

Selective fading outage [cont.] Network Planning - Network Planning Method

1 - 2 - 83

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

Kn 2 × (C m ) 2 Ts

Ps = 4.3 × D × where:

(

= 1 exp 0.2 × P0

K n = Ts !f o

Ts

10

0.75

)

Bc 20

r

!fo = signature bandwidth [GHz] Bc = notch producting a given BER [dB] Ts = symbol time depending on capacity and modulation [ns] m = echo delay mean value [ns] 1. 3

m

d r

d [ns ] 50 = hop length [km]

= 0.7

= reference delay [6.3 ns]

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6 Propagation model

Selective fading outage Network Planning - Network Planning Method

1 - 2 - 84

Signature

Bc

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6 Propagation model

Exercise

Network Planning - Network Planning Method

1 - 2 - 85

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

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6 Propagation model

Single channel global outage 1 - 2 - 86

Network Planning - Network Planning Method

The outage time can be expressed, in the most general form, as the weighted sum of two different contributions concerning flat and selective fading. a 2

P = Pf + Ps

a 2

2 a

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

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Network Planning - Network Planning Method

1 - 2 - 87

7 Quality objectives of Digital Radio Links

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 87

7 Quality objectives of Digital Radio Links

Introduction

1 - 2 - 88

Network Planning - Network Planning Method

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.

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 88

7 Quality objectives of Digital Radio Links

ITU-T recommendations 1 - 2 - 89

Network Planning - Network Planning Method

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 (64 kbit/s)

At or Above Primary Rate (> 2 Mbit/s)

At or Above Primary Rate (> 2 Mbit/s)

Errored Bits

Errored Blocks

Performance criteria

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Errored Blocks

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 89

7 Quality objectives of Digital Radio Links

Error Performance Events 1 - 2 - 90

Network Planning - Network Planning Method

Time 10 sec

< 10 sec

Unavailability detected Unavailable period

10 sec

Availability detected Available period

Severely Errored Second Errored Second (non-SES) Error-free Second

Example of unavailability determination

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Note: Within brackets is explained the event for G.821. ES - Errored Second If one or more errored block (or bit) events occur within one second, an errored second event is generated. SES - Severely Errored Second A one-second period which contains $30% of errored blocks (or BER $10-3). SES is a subset of ES. BBE - Background Block/Bit Errors An errored block (or bit) not occuring as part of an SES. UAS - UnAvailable Second Consecutive 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.

3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 90

7 Quality objectives of Digital Radio Links

Impact of propagation on performance objectives 1 - 2 - 91

Network Planning - Network Planning Method

Performance Impairment

Degradation Period

Performance Objective

Rain

>10 seconds

Availability

Multipath Fading

< 10 seconds

Error Performance (SES)

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 91

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 92

Network Planning - Network Planning Method

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 operating mainly 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 typically operating equal to, or lower, than 2 Mbit/s. - RADIO NETWORK PLANNING

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 92

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 93

Network Planning - Network Planning Method

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.

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 93

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 94

Network Planning - Network Planning Method

G.821 Basic apportionment principles

1250 Km

27500 Km

25000 Km

1250 Km

T-reference point

T-reference point Local grade

Medium grade

High grade

Medium grade

Local grade

Objectives allocation

15%

15%

40%

15%

15%

SESR

0.00015

0.00015

0.0004

0.00015

0.00015

0.001

ESR

0.012

0.012

0.032

0.012

0.012

0.08

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 94

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 95

Network Planning - Network Planning Method

G.821 related specs High grade Performance Objectives

HDRP

Medium grade

Local grade

Rec. 594

Real link

Rec. 697

Rec. 634 Rec. 696

Availability Objectives

HDRP

Rec. 557

Real link

Rec. 695

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Rec. 1053

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 95

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 96

Network Planning - Network Planning Method

ITU-R Rec. 557 Unavailability objective for HDRP (2500 km) high grade link: •Unavailability < 0.3 %

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 96

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 97

Network Planning - Network Planning Method

ITU-R Rec. 695 Unavailability objective for high grade real link: •Unavailability

< 0.3x

L % (L 2500km) 2500

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 97

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

Network Planning - Network Planning Method

1 - 2 - 98

ITU-R Rec. 594 Quality performance for the HDRP (2500 km) should not exceed the following values. • SES < 0.054% = 0.004% + 0.05% • ES

< 0.32%

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 98

7 Quality objectives of Digital Radio Links

ITU-T G.821 [cont.]

1 - 2 - 99

Network Planning - Network Planning Method

ITU-R Rec. 634 High grade real link Quality performance should not exceed the following values scaled depending on the link length • SES <

• ES<

L x 0.054% (L 2500km) 2500

L x 0.32% (L 2500km) 2500

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 99

7 Quality objectives of Digital Radio Links

ITU-T G.821

1 - 2 - 100

Network Planning - Network Planning Method

ITU-R Rec. 696 Medium grade real links are divided in 4 quality classes with different objectives:

Performance Parameters

Percentage of any month H.G. Class 1 280 km

M.G. Class 2 280 km

M.G. Class 3 50 km

M.G. Class 4 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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 100

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 [cont.] 1 - 2 - 101

Network Planning - Network Planning Method

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.

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 101

7 Quality objectives of Digital Radio Links

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

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 102

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 [cont.] 1 - 2 - 103

Network Planning - Network Planning Method

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 103

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 [cont.] 1 - 2 - 104

Network Planning - Network Planning Method

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 104

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 [cont.] 1 - 2 - 105

Network Planning - Network Planning Method

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

Mbit/s ESR G.826

1.5 - 5

5 - 15

15 - 55

0.04

0.05

0.075

0.16

0.02

0.04

5*10-5

5*10-5

SESR

0.002

BBER

2*10-4

ESR

0.01

0.01

5*10-5

5*10-5

SESR G.828

BBER SEP

55 - 160

0.002 t.b.d.

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 105

7 Quality objectives of Digital Radio Links

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

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 106

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 [cont.] 1 - 2 - 107

Network Planning - Network Planning Method

G.826-8 Basic apportionment principles Total objectives 100% 27500 km

Country based portion 45%

National portion 35%

Distance based portion 55%

International portion 10%

Terminating country 1% (2)

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

Transit country 2% (4)

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 107

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 [cont.] 1 - 2 - 108

Network Planning - Network Planning Method

G.826-8 Country based apportionment 27500 Km Terminating country

Transit countries

Terminating country

PEP

Objectives allocation

PEP

National portion

International portion

National portion

17.5%

10%

17.5%

1%

2%

2%

2%

2%

45%

1%

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 108

7 Quality objectives of Digital Radio Links

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

1 - 2 - 109

G.826-8 - Allocation to the National/International Portion of the endto-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 - RADIO NETWORK PLANNING

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 109

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 1 - 2 - 110

Network Planning - Network Planning Method

G.826/8 related recommendations

Performance Objectives

International portion

National portion

HDRP

Rec. F.1092

Rec. F.1189

Real link

Rec. F.1397

Rec. F.1491

HDRP

---

---

as G.821

as G.821

Availability Objectives Real link

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 110

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1092 [cont.] 1 - 2 - 111

Network Planning - Network Planning Method

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

BL = BR x .02 x

L LREF

BL = BR x .02

Terminating country

if Lmin < L < LREF

BL = BR x .01x

L > LREF

BL = BR x .01

if

L LREF / 2

if Lmin < L < if

LREF 2

L > LREF / 2

Where: BR = Block allowance ratio (0 < BR < 1) Lmin = 50 km - RADIO NETWORK PLANNING

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 111

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1092 1 - 2 - 112

Network Planning - Network Planning Method

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 112

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1397 [cont.] 1 - 2 - 113

Network Planning - Network Planning Method

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 113

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1397 [cont.] 1 - 2 - 114

Network Planning - Network Planning Method

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

Parameter ESR

Bit rate

Lmin < Llink < 1000 km

(Kbit/s)

B1

1664

10-4

5x

C1

1000 km < Llink B2

(1+BR)

0

5x

C2

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

BBER

150336

2.5 x 10-6 (1+BR)

0

2.5 x 10-6

5 x 10-6 (1+BR)

0

5 x 10-6

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10-6 x BR 2 x 10-6 x BR

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 114

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1397 [cont.] 1 - 2 - 115

Network Planning - Network Planning Method

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

Parameter ESR ESR ESR

Bit rate

Lmin < Llink < 500 km

(Kbit/s)

B3

1664

5x

10-4

5x

10-4

5x

10-4

2240 6848

10-3

500 km < Llink C3

(1+BR) (1+BR) (1+BR)

0 0

C4

5x

10-4

10-4

x BR

5x

10-4

10-4

x BR

5x

10-4

10-4

x BR

0

10-3

2 x 10-4 x BR

ESR

48960

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)

BBER

150336

(1+BR)

0

B4

5 x 10-6 (1+BR)

0

2.5 x 10-6

0

5 x 10-6

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5 x 10-7 x BR 10-6 x BR

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 115

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1397 [cont.] 1 - 2 - 116

Network Planning - Network Planning Method

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

Parameter

Bit rate

Lmin < Llink < 1000 km

(Kbit/s)

B1

ESR

1.5-5

2x

10-3

ESR

>5-15

ESR

1000 km < Llink C1

(1+BR)

B2 10-4

C2 8 x 10-4 x BR

0

5x

2.5 x 10-3 (1+BR)

0

5 x 10-4

>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

10-3 x BR

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 116

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1397 1 - 2 - 117

Network Planning - Network Planning Method

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

Parameter

Bit rate

Lmin < Llink < 500 km

(Kbit/s)

B3

ESR

1.5-5

2x

10-3

ESR

>5-15

ESR

500 km < Llink C3

(1+BR)

B4 10-3

C4 4 x 10-4 x BR

0

2x

2.5 x 10-3 (1+BR)

0

2.5 x 10-3

5 x 10-4 x BR

>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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 117

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1189 [cont.] 1 - 2 - 118

Network Planning - Network Planning Method

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 PEP

LE

Access

PC/SC/TC

Short Haul

IG

Long Haul

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 118

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1189 1 - 2 - 119

Network Planning - Network Planning Method

The values for the B parameter are fixed as following: A1 + .001*L/500

long haul ( 1%
7.5%
short haul

7.5%
access Mbit/s

1.5-5

5-15

15-55

55-160

rel="nofollow">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%.

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 119

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1491 [cont.] 1 - 2 - 120

Network Planning - Network Planning Method

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 120

7 Quality objectives of Digital Radio Links

Rec. ITU-T G.826 and G.828 - ITU-R F.1491 1 - 2 - 121

Network Planning - Network Planning Method

Long haul

A = (A1 + 0.002) x

Llink 100

A = A1 + 0.00002 x Llink

for50km< Llink < 100km for Llink > 100 km

where A1 provisionally been agreed in 0.01
Short haul and access: 7.5% < A < 8.5% Mbit/s

1664 VC-11 TC-11

2240 VC-12 TC-12

6848 VC-2 TC-2

48960 VC-3 TC-3

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

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150336 VC-4 TC-4

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 121

7 Quality objectives of Digital Radio Links

Exercise

Network Planning - Network Planning Method

1 - 2 - 122

Exercise 1 - Unavailability due to the propagation Calculate the unavailability due to the propagation in a 60 km link (using Rec. 695). Exercise 2 - SES calculation Calculate 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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 122

Network Planning - Network Planning Method

1 - 2 - 123

8 Fading countermeasures

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8 Fading countermeasures

Adopted techniques 1 - 2 - 124

Network Planning - Network Planning Method

Techniques adopted to reduce the multipath fading impairment: Adaptive Signal Equalization at the Receiver Diversity Reception: • Space Diversity • Frequency Diversity • Angle Diversity

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8 Fading countermeasures

Adaptive equalization [cont.] 1 - 2 - 125

Network Planning - Network Planning Method

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.

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8 Fading countermeasures

Adaptive equalization [cont.] 1 - 2 - 126

Notch Depth [dB]

Network Planning - Network Planning Method

Without Equalizer

With Equalizer

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

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8 Fading countermeasures

Diversity Improvement [cont.] 1 - 2 - 127

Network Planning - Network Planning Method

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

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8 Fading countermeasures

Diversity Improvement [cont.] 1 - 2 - 128

Network Planning - Network Planning Method

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

(

m = D 1 K2

)

where

is the multipath activity parameter

The outage probability for a protected channel is:

(

)

PDIV BER rel="nofollow"> 10 n =

Pi • Pj m

The corresponding improvement is:

I=

Pi m = PDIV Pi

where “Pi” is the probability without protection

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8 Fading countermeasures

Diversity Improvement [cont.] 1 - 2 - 129

Network Planning - Network Planning Method

a) Frequency diversity

Kf2 = exp(- 0.9• JF• Cm )

!F = frequency diversity [GHz]

b) Space diversity

m

* K = exp ( 4 • 10 () 2 s

S = antenna separation [m] (Max. = 200

6

•

S 7

2

d = median hop delay [ns] =0.7 50 where d = hop length [km]

1.3

' % %&

in this formula)

= 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:

Kfs2 = Ks2 • Kf2 If four antennas are used to obtain the space diversity also in the other side, the formula is: 2 2 2 Kfs2 = Ks1 • Ks2 • Kf

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8 Fading countermeasures

Diversity Improvement [cont.] 1 - 2 - 130

Network Planning - Network Planning Method

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

m 4 = D3 • det K 4

where

is the multipath activity parameter

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

1 det K 4 =

K12

K 21 1

K13

K14

K 23

K 24

K 31

K 32 1

K 41

K 42

K 34

K 43 1

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Diversity Improvement 1 - 2 - 131

Network Planning - Network Planning Method

f

1 1 2

S

S

1

2

3 f

2

4

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.

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8 Fading countermeasures

Frequency diversity 1 - 2 - 132

Network Planning - Network Planning Method

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 standby 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

Rx1 Dem BB f1 f2

Tx2

Rx2 Dem BB

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Exercise

Network Planning - Network Planning Method

1 - 2 - 133

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

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Space diversity 1 - 2 - 134

Network Planning - Network Planning Method

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. Rx1 Dem BB f S

Tx1 f

Rx2 Dem BB

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Exercise

Network Planning - Network Planning Method

1 - 2 - 135

Exercise - Space diversity improvement Calculate the space diversity improvement by using the following data: Vertical antenna separation : 8m Frequency : 8 GHz ( =3.75 cm) Multipath occurrence factor Po : 1 Outage probability without protection : 0.0001

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8 Fading countermeasures

Space and frequency diversity [cont.] 1 - 2 - 136

Network Planning - Network Planning Method

a) 2 Receivers Tx1

Rx1 Dem BB f1 S f2

Tx2

Rx2 Dem BB

Diversity in reception side only

f1 Tx1

Rx1 Dem BB

S2

S1 f2 Tx2

Rx2 Dem BB

Diversity in transmission and reception sides

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Space and frequency diversity 1 - 2 - 137

Network Planning - Network Planning Method F1

b) 4 Receivers

Rx1

F1

1/f1

Tx1

3/f2

F1

DEM

BB

DEM

BB

DEM

BB

DEM

BB

Rx2

F2

Tx2

4/f2

2/f1

F2

Rx3 F2

Rx4

1+1 configurations with 4 receivers

F1

F1

1/f1

Tx1

Rx1 3/f2

S1 2/f1

F2

Tx2

F1

S2

4/f2

Rx2 F2

Rx3 F2

Rx4

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

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Angle diversity Network Planning - Network Planning Method

1 - 2 - 138

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 with Beam Diversity; lower costs. Disadvantages: Less diversity improvement.

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1 - 2 - 139

Network Planning - Network Planning Method

9 Reflections from ground

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9 Reflections from ground

Reflections from ground Network Planning - Network Planning Method

1 - 2 - 140

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.

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9 Reflections from ground

Geometrical model 1 - 2 - 141

Network Planning - Network Planning Method

Tx

D 1

R1

P

2 R2

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Geometrical parameters related to the Reflection mechanism: • Reflection point P • Grazing angle • 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).

3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 141

9 Reflections from ground

Rx signal with reflection 1 - 2 - 142

Network Planning - Network Planning Method

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 l; 360 deg. phase shift for each l) • reflection shift: depends on frequency, grazing angle, and surface type (usually close to 180 deg).

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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).

9 Reflections from ground

Rx signal level 1 - 2 - 143

Network Planning - Network Planning Method

Tx

Rx

Rx Level

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9 Reflections from ground

Exercise

Network Planning - Network Planning Method

1 - 2 - 144

Why does the reflected ray from the ground change?

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9 Reflections from ground

Space diversity in reflection paths 1 - 2 - 145

Network Planning - Network Planning Method

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).

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9 Reflections from ground

Exercise

Network Planning - Network Planning Method

1 - 2 - 146

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

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1 - 2 - 147

Network Planning - Network Planning Method

10 Frequency re-use

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10 Frequency re-use

Introduction [cont.] Network Planning - Network Planning Method

1 - 2 - 148

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

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10 Frequency re-use

Introduction Network Planning - Network Planning Method

1 - 2 - 149

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.

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10 Frequency re-use

Terminology 1 - 2 - 150

Network Planning - Network Planning Method

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

The appearance, during the propagation, of a polarization component which is orthogonal to the expected polarization. For one radio wave transmitted on a given polarization, the ratio the reception side of the power received with the expected polarization to the power received with the orthogonal polarization. Note - the cross-polarization discrimination depends both on the characteristics of the antenna and on the propagation medium.

Cross-polarization isolation

Depolarization

For two radio waves transmitted with the same frequency with the same power and orthogonal polarization, the ratio of the copolarized power in a given receiver to the cross-polarized power in that receiver. A phenomenon by virtue of which all or part of the power of a radio wave transmitted with a defined polarization may no longer have a defined polarization after propagation.

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10 Frequency re-use

Exercise

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1 - 2 - 151

What is the difference between XPD and XPI?

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10 Frequency re-use

Concepts

1 - 2 - 152

Network Planning - Network Planning Method

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) - RADIO NETWORK PLANNING

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10 Frequency re-use

Interferences 1 - 2 - 153

Network Planning - Network Planning Method

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 type 2. 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 - RADIO NETWORK PLANNING

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10 Frequency re-use

Interference types 1 - 2 - 154

Network Planning - Network Planning Method

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) z H (V) V (H)

Return (Go)

x 1 1r

2r 2

y 3 3r

4r 4

N Nr

1' 2'r 3' 4'r 1'r 2' 3'r 4'

N' N'r

fo

B

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10 Frequency re-use

Frequency reuse system block diagram 1 - 2 - 155

Network Planning - Network Planning Method

Single antenna, Double polarity

LO H

DATA IN H

MOD

UP CONV

TX

H

H

RX

DOWN CONV

DATA H

IF

V

DEM

& XPIC

OUT

H

LO DATA IN

V

MOD

UP CONV

TX

V

V

RX

DOWN

V

IF

CONV

H

DATA

DEM

& XPIC

OUT

V

V LO

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10 Frequency re-use

Same frequency re-used channel (cross-polar) 1 - 2 - 156

Network Planning - Network Planning Method

EXAMPLE: 1 dB WORSENING DUE TO C/I MODULATION mod 128 cross MODULATION mod 128 cross INTERF. CALC.

C/N E-3 dB 23

C/I dB 30

C/N E-3 dB 23

Rx THRESHOLD dBm -71.0

Rx PW dBm -30.00

XPI dB -35.00

XPIC GAIN dB -16.00

TOTAL dBm -81.00

C/I = 51 dB

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

C I

Degradation(dB) = 10 log 1 + 10 10

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10 Frequency re-use

Exercise

Network Planning - Network Planning Method

1 - 2 - 157

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

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10 Frequency re-use

Adjacent frequency re-used channel (co-polar) 1 - 2 - 158

Network Planning - Network Planning Method

EXAMPLE: 1 dB WORSENING DUE TO C/I MODULATION mod 128 cross

INTERF. CALC.

C/N E-3 dB 23

C/I dB 30

PRX dBm -30.00

NFD dB -27.00

TOTAL dBm -55.00

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

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Prediction of outage due to multipath propagation [cont.] 1 - 2 - 159

Network Planning - Network Planning Method

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)

40

for XPDg > 35

XPD0 =

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.

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Prediction of outage due to multipath propagation [cont.] 1 - 2 - 160

Network Planning - Network Planning Method

Step 2:

Evaluate the multipath activity parameter ( )

Step 3:

Determine

Q = - 10 • log

k xp D P0

0.7

one transmit antenna

kXP = * S 1 - 0.3 exp (- 4x10 -6 t 7 ()

2

' % %&

two transmit antennas

In the case where two orthogonal polarized transmissions are from different antennas: vertical separation is “St“(m) carrier wavelength is “ ” (m)

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10 Frequency re-use

Prediction of outage due to multipath propagation 1 - 2 - 161

Network Planning - Network Planning Method

Step 4:

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

Pxp = P0 • 10

-

M XPD 10

where MXPD is the equivalent XPD margin for a reference BER given by: Co co-channel without XPIC I Co co-channel with XPIC XPIRF : 15 - 20 dB XPD 0 + Q + XPIRF I C adjacent channel XPD 0 + Q + NFD - o I XPD 0 + Q -

MXPD =

where Step 5:

Co I

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

Evaluate the overall outage as the unweighted sum of partial outages related to flat fadding, selective fading and frequency re-use. Ptot = Pf + Ps + Pxp

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10 Frequency re-use

Prediction of outage due to rain effects [cont.] 1 - 2 - 162

Network Planning - Network Planning Method

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 semiempirical formula:

XPD2 = XPD1 20 log(f2/f1 )

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).

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10 Frequency re-use

Prediction of outage due to rain effects [cont.] 1 - 2 - 163

Network Planning - Network Planning Method

Step-by-step procedure for predicting outage due to precipitation effects (Rec. ITU-R P.5307): 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):

Ap =10((U

C0/I + XPIRF)/V)

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.

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10 Frequency re-use

Prediction of outage due to rain effects 1 - 2 - 164

Network Planning - Network Planning Method

Step 3:

Determine the following parameters:

[

]

23.26log Ap / 0.12A0.01

if m < 40

40

if m > 40

m=

and

(

)

n = -12.7+ 161.23- 4m /2 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:

PXPR = 10(n

2)

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1 - 2 - 165

Network Planning - Network Planning Method

11 Interferences

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11 Interferences

Introduction 1 - 2 - 166

Network Planning - Network Planning Method

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 overreach condition

5

Different services sharing the same frequency band (interferences generated by radio links 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)

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11 Interferences

Modem performances 1 - 2 - 167

Network Planning - Network Planning Method

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/N

W/O FEC (dB)

10^-3 mod level QAM 512 256 128 64 32 16

33.00 30.00 27.00 24.00 21.00 18.00

10^-6

C/I causes 1 dB worsening

C/I causes 0.5 dB worsening

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

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

10^-3

36.50 33.00 30.00 27.00 24.00 21.00

39.00 36.00 33.00 30.00 27.00 24.00

10^-6

42.50 39.00 36.00 33.00 30.00 27.00

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10^-3

42.00 39.00 36.00 33.00 30.00 27.00

10^-6

45.50 42.00 39.00 36.00 33.00 30.00

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 167

11 Interferences

Local sources [cont.] 1 - 2 - 168

Network Planning - Network Planning Method

Transmitter to receiver interference INTERFERENCE Type "1" SPECTRUM Type "A" for digital to digital or "B" for analog to digital interference Type "C" ACTIVITY

WEST

EAST INTERFERENCE

TX TO RX

PTx1

PRx2

ANTENNA 1

ANTENNA 2

AF1= ATTEN. FEEDER 1

AF2= ATTEN. FEEDER 2

TX1

RX2

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 168

11 Interferences

Local sources 1 - 2 - 169

Network Planning - Network Planning Method

Transmitter to receiver interference: calculation example INTERFERENCE CALCULATIONS Site of calculations West site East Site

TX on RX Type

MILAN FLORENCE VENICE

INPUT DATA (example) PTX1 Power TX at radio circulator antenna port PRx thr. PRx at threshold 10^-3 AF1 AF2 D A NFD

Attenuation feeder West Attenuation feeder East Angle between antennas Attenuation provided by West + East ant Net filter discrimination (for co-channel)

As example see A, B

OUTPUT DATA dBm dBm dB dB deg. dB dB

30.00 C/I results (at threshold) -72.00 level of C/I West on East 0.00 0.00 80.00 for 2 antennas 130.00 0.00

dBm

-100.00

dB

B

28.00

+ -

Threshold 10^-3 level of TX West signal on East RX

COMPUTED DATA level of TX West signal on East RX

A

+ -

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Power TX at radio circulator antenna port Attenuation feeder West Attenuation provided by West + East ant Attenuation feeder East

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 169

11 Interferences

Signals belonging to the same system at a common location [cont.] 1 - 2 - 170

Network Planning - Network Planning Method

Receiver to receiver interference INTERFERENCE SPECTRUM ACTIVITY

Type "2" Type "A" for digital to digital or "B" for analog to digital interference Type "D" (depending on fading activity) WEST

EAST INTERFERENCES

Rx to Rx

I

PR1*

I W

W

ANTENNA 1 G1= ANTENNA 1 GAIN

PR2* ANTENNA 2

G2= ANTENNA 2 GAIN

AF1= ATTEN. FEEDER 1

AF2= ATTEN. FEEDER 2

PR1= RX1 INPUT SIGNAL

PR2= RX2 INPUT SIGNAL

RX1

RX2

* power field at antenna input - RADIO NETWORK PLANNING

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 170

11 Interferences

Signals belonging to the same system at a common location 1 - 2 - 171

Network Planning - Network Planning Method

Receiver to receiver interference: calculation example Site of calculations

MILAN

West site

FLORENCE VENICE

East Site

INPUT DATA

As example see A, B, C

OUTPUT DATA

PRx thr. PRx at threshold 10^-3 G1 Gain antenna West

Various C/I results (at threshold)

dBm

-72.00

dB dB

40.00 43.00

level of C/I West H on East H level of C/I West H on East V

dB dB

5.00

25.00 28.00

G2

Gain antenna East

AF1 AF2

Attenuation feeder West

level of C/I West V on East V

dB

25.00

Attenuation feeder East

dB

5.00

level of C/I West V on East H

PR1

Rec. Power at Rx West

dBm

-30.00

level of C/I East H on West H

dB dB

28.00 26.00

PR2 D

Rec. Power at Rx East Angle between antennas

dBm deg.

-30.00 94.00

level of C/I East H on West V level of C/I East V on West V

dB dB

30.00 26.00

HH HV

dB dB

65.00 69.00

level of C/I East V on West H

dB

30.00

VV VH ATTEN Attenuation provided by East antenna HH ATTEN Attenuation provided by East antenna HV ATTEN Attenuation provided by East antenna VV ATTEN Attenuation provided by East antenna VH

dB dB

65.00 69.

dB

70.00

dB

73.00

dB dB

70.00 73.00

BRANC RX branching insertion loss West

dB

2.00

dB

ATTEN Attenuation provided by West antenna ATTEN Attenuation provided by West antenna ATTEN Attenuation provided by West antenna ATTEN Attenuation provided by West antenna

C

+ PRX at threshold 10^-3 - level of East H signal on West H ant.

BRANC RX branching insertion loss East dB 2.00 NFD Net filter discrimination (for co-channel) dB 0.00 COMPUTED DATA * power field at antenna input PR1* PR2*

Power Rx at antenna direction West

dBm

-63.00

Power Rx at antenna direction East

dBm

-66.00

level of West H signal on East H ant. level of West H signal on East V ant. level of West V signal on East V ant.

dBm dBm dBm

-97.00 -100.00 -97.00

level of West V signal on East H ant.

dBm

-100.00

level of East H signal on West H ant.

dBm

-98.00

level of East H signal on West V ant. level of East V signal on West V ant.

dBm dBm

-102.00 -98.00

level of East V signal on West H ant.

dBm

-102.00

A

Rec. Power at Rx West

+ Attenuation feeder West - Gain antenna West + RX branching insertion loss West B

Power Rx at antenna direction West

+ -

Attenuation provided by East antenna HH Gain antenna East Attenuation feeder East Net filter discrimination (or filter attenuation) RX branching insertion loss East

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 171

11 Interferences

Signals belonging to the same system from other locations 1 - 2 - 172

Network Planning - Network Planning Method

INTERFERENCE

Type "3"

SPECTRUM

Type "A" for digital to digital or "B" for analog to digital interference

ACTIVITY

Type "D"

I C w B

A

Interfered signal received power PRXCW = PTXAW - BTXAW + GTXAW - FSLAC + GRXCW - BRXC Interfering signal received power PRXCint = PTXAint - BTXAint + GTXAint - DGTXAint - NFD - FSLAC + GRXCW - BRXC

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 172

11 Interferences

Signals belonging to the same system from other locations through an overreach condition 1 - 2 - 173

Network Planning - Network Planning Method

INTERFERENCE SPECTRUM ACTIVITY

Type "4" Type "A" for digital to digital or "B" for analog to digital interference Type "D"

w I

D

A

I

B

C

w E

F

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

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 173

11 Interferences

Exercise

Network Planning - Network Planning Method

1 - 2 - 174

Exercise - Threshold degradation Calculate the threshold degradation due to a -95 dBm co-channel interference signal on the following system. Rx threshold = -72 dBm C = 23 dB N

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Blank Page Network Planning - Network Planning Method

- RADIO NETWORK PLANNING

1 - 2 - 175

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 175

1 - 2 - 176

Network Planning - Network Planning Method

End of Module

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3FL 42104 AAAA WBZZA Edition 2 - July 2005 Section 1 - Module 2 - Page 176