Curso System Planning

7/31/2019 Curso System Planning

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System planning. Slide 2

Wave propagation

k-values

ducting

multipath

Terrain profiles

Fresnel zones

Earth bulge

Reflections

Field Survey

Procedures

Equipment

Survey Report

Agenda - Day 1

Antennas

gain

X-polarisation

passive reflectors

Power budget

Free space loss

Link budget

Precipitation

Characteristics

Unavailability due to rain


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Performance objectives

G.821 & G.826

Performance Predictions Fading margin

Multipath fading

Diversity Space diversity

Frequency diversity

Path diversity

Agenda - Day 2

Interference

Cross polar interference

Adjacent channel

Co-channel

Frequency Planning

Alternated channel plan

CCDP

Equipment configurations

Trunk radio

Access radio


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Wave propagation in theatmosphere

Chapter


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Wave Propagation in the Atmosphere

It is the radiowaves interaction with the molecules in the

atmosphere that bends them.

As for visible light, the radiowaves may be treated withray optics on a large scale.

no atmosphere with atmosphere

straight rays bent rays

d


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Fundamentals of Ray Optics

2

1 1'

Incident ray Reflected ray

n1

n2

Refracted ray

- The angle of incidence equals the angle of reflection1='1

- For a given frequency the angles of incidence, 1,and refraction, 2, are related by

n1.sin1 = n2.sin2 (1)

- The relation (1) is called Snell's law. n1 and n2 areconstants characteristic of the media.These constant are called indices of refraction

Cn= __ (2 )

V

c is the speed of light in vacuum and v is the speed ofthe waves in the given medium.

The rays bend towards the denser medium


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c

n = 1 . 3 3w

n = 1

water surface

The pool experiment

c

Why is ? c c


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The index of refraction for air, for the frequency of interest is very close tothat of vacuum. Due to that, one uses N, radio refractivity, instead of n

N = (n-1) .106

N = . (p+4810 . )77.6

T

e

T

(3)

(4)

Since p, e and T all are functions of height also N is a function of height

T is temperature in Kelvin. Degrees in Celsius + 273.15

p is total air pressure in hPa (=mbar)

e is water vapour pressure in hPa

-

-

-

The index of refractionfor the atmosphere


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Ray bending (refraction) (K=1.33)

Earth curvature

N-units

h [km]

- 40

dN/dh = -40 K=1.33

dense air

less dense air

* For a normal atmosphere (standard, well mixed) the variation ofNwith height is

km

unitsN40=

dh

dN

The rays bend towards the

region of higher refractivity

(densest).


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K - value

K-value is a common used value to indicate ray bending. It includes both:

Ray curvature

Earth radius

6101

1

1

1

cos1

(1

11

1

1+

=+

=

=

dh

dNa

dh

dna

dh

dn

na

ra

K

n nearly one is nearly zero

For a normal atmosphere dN/dh=-40 : 33.1

10)40(63701

16

=

+

= K

h(km)

3

2

1

K= -2/3

0 300

N-UNITS

4/3 1 2/3

EARTH RADIUSa = 6370 km

K

-2/34/3

RT1

2/3

K=, ray is parallel with the earth

R b di ( f i )


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Ray bending (refraction)

N-units

h [km] 0

dN/dh = 0 K=1

Equaldistributeddensity

Same as no atmosphere

km

unitsN0=

dh

dN

(K=1, subrefracted)

Earth curvature

N-units

h [km]

km

unitsN78=

dh

dN

Earth curvature

dense air

less dense

air

78

dN/dh =78 K 0.66(K=0.66, subrefracted)

- humid air

N-units

h [km]

Earth curvature

>- 157

dN/dh < -157 K


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Transmitter situated in a ground-based duct

157+=dh

dN

dh

dMIn duct, close to earth: Uniform dM/dh-157N/km)

N - value

dN/dh=-157

Martin P M Hall


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Atmospherical Multipath Propagation

h

Re flectingAtmospheric

Layer Boundar y

M= M1-M2

M1 M2 M

x

T 4

R13

REGION 1

d

REGION 2

2

z1 12

Multipath propagation occurs when there are more than one ray reaching the receiver.Multipath transmission is the main cause of fading.

Multipath can only happen when dN/dh varies with height.

Ground base duct

The figure shows a ground based duct. The atmosphere has a very dense layer at theground with a thin layer on top of it. There will be nearly total reflection from this layerboundary.

157+=dh

dN

dh

dM


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Elevated duct

157+=dh

dN

dh

dM

Rays propagating from a transmitter situated below an elevated duct.

Martin P M Hall


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Formation of a Duct

Daytime

Convectionmixes theatmosphere

No convection

Temperature-

inversion

dMdh >0

dMdh


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Ducting ProbabilityThe figure shows the percentage of time the dN/dh is less than -100 N units/km in May.

This figure gives a good indication where it is most likely to experience ducting. It is seenfrom the figure that the equatorial regions are most vulnerable to ducts. In temperateclimate the probability of formation of ducts is less.

This difference in duct probability can be explained by the difference in temperature andmost of all by the difference in humidity.


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Terrain profiles

Chapter


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The Bristol channel path


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The Bristol channel pathSite:ILFRACOMBE

Altitude:203.0 m amsl.Antenna:10.00 m.

Site:ST. HILARY

Altitude:126.0 m amsl.Antenna:10.00 m.

Path length:58.65 km.

K:1.33 Fresnel zone:1.00Frequency:7.70 GHz.Grazing angle:3.47 millirad.

0.0 15.0 30.0 45.0Distance in km.

0

50

100

150

200

250


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Drawing path profile

Earth curvature

Earth curvature

Refraction

Refraction

Earth bulge - Refraction

Refraction - Earth bulge


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Earth bulge

In order to draw the line of sight straight in a path profile, the raybending due to variations in k value is added to the terrain heights.

The modification of the terrain heights is give by

M=d1 . d2

12.74 . k

d1 , d2 distanes in km

SITE A SITE B

k= 0.6

k= 1.33

k=8

M

Real ground height from map

d1 d2

k - k value. Includes both earth and ray curvature


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Fresnel zone

TheFresnel zoneis the locusof pointswhere

d3 - (d1 + d2) = /2

TheradiusF1 isapproximately F1 = 17.3

f - frequency in GHz d1, d2 andd=d1 + d2 inkm

d1 . d2f . d

m

d3

d1 d2

F1

BA


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ITU-R clearance criteria

Ref. ITU-R P.530-7

1. Determine the antenna heights required for clearance for the first Fresnel zone (F1)over the highest obstacle calculated with k= 4/3

2. Obtain the value ofke (99.9%) from figure below for the path length. And calculate

the antenna heights required for the value ofke and the following Fresnel zone

clearance radii:

0.5

0.6

0.7

0.8

0.9

1

10 10020 50

path length in km

ke

3. Use the larger of the antenna heights obtained by steps 1. and 2.

Temperate climate Tropical climate

0.0 F1 if there is asingle isolated pathobstruction.

0.3 F1 if the pathobstruction isextended along aportion of the path.

0.6 F1 for pathlengths greaterthan about 30 km.


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0

10

20

30

40

50

60

70

80

90

100

10 15 20 25 30 35 40 45 50 55 60

Path length [km]

Antenn

aheight[m]

2 GHz

4 GHz

6 GHz

8 GHz

11 GHz

15 GHz

Antenna heights for a hop over flat terrain

Clearance criteria according to ITU-R P.530


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Diffraction loss

Diffraction loss for obstructed line-of-sight microwave radio paths

Ref. ITU-R P.530-7


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Ground reflections

Tx

Rx

The more conductive the ground is,the stronger the reflection will be.

(sea mash, etc.)

Received signalis the sum of the

direct andreflected rays.

Typical reflection coefficients


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Typical reflection coefficientsfor different types of terrain

hillswith

trees

hillswithbushes

cultivatedfields

steppe

swithnoveg

etation

water

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0


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Height - Gain Curves

Received signal sum of directand reflected rays

To counteract the effect of groundreflectionsone uses space diversity

One antenna at maximum and one atminimum signal strength

Signalstrength as function of height

weak signalstrongsignal

this curvevaries with k


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Optimum antenna separation

1(2)


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Design methods

1. Analytical

using series expansion

2. Geometricalusing Fresnel zones

Methods for finding reflection point and optimumantenna separation:

D i i f h fl i i


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Determination of the reflection point

21

21

hhhhq

+=

q - parameter to be used in formulas

h1 - height of antenna above reflection point at site A in m

h2 - height of antenna above reflection point at site B in m

2

21

2

)(51

d

hhkQ

+

=

Q - parameter to be used in formulas

k - effective Earth radios factor

d- total path length in km

Q

qV

1

1+

=

V - parameter to be used in formulas

= +

=0

2

)1(ii

i

Q

VVZ

h2

h1

d1 d2

d=d1 +d2

D i i f h fl i i


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Determination of the reflection point

Simplification:

( ) ( )Z V

V

Q

V

Q

V

Q +

++

++

+

1 1

31

121

2 4

2

6

3

( )dd

Z1 21= +

( )dd

Z d d2 121= =

O ti t ti


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LRx

1(2)h

1(2)

Difference in path length:

Optimum antenna separation

=

2

12 74 12 74101

1

2

2

2

2

3

dh

d

kh

d

k. .

Corresponding pitch distance:

1

2

2

2

30 3

2

1

12 74

10=

.

.

d

f

h

d

k

21

1

2

30 3

2

1

12 74

10=

.

.

d

fh

d

k

Optimum antenna separation:

2

11

=h

at site 1

at site 2

2

22

=hat site 1 at site 2


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Field survey

Chapter

What is a s r e ?


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What is a survey ?

A visit in the field in order to plan a microwavesystem.

A visit in the field to already planned microwavesites in order to verify the feasibility of thesystem.

A study of the propagation conditions for aplanned system.

A study of the infrastructure in an area where amicrowave system is planned.

Objectives of a field survey


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Verify exact site location.

Verify line-of-sight

Confirm space in existing stations

Check propagation conditions

Check frequency interference possibilities

Check soil conditions for new towers

Check site access and infrastructure in the area

Objectives of a field survey

Survey procedures


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Survey procedures

PreparationsMap Work. Locating sites on the map.Making of path profiles. Check line-of-sight, antenna heights, organizingtransport and accommodation.

Field workLocation of sites. Check if the terrain at the chosen map locations isconvenient.Verify position and altitude of the sites.Verify line-of-sight between sites. Check altitude of obstacles.Measure up and marking of site area.Soil investigations.Checking of site access. Road construction.

Investigate propagation conditions.Make interference measurements.

Survey reportReport from the findings and calculations of system quality has to be done.

Geodetic Datum


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Geodetic Datum

Hundreds of different datums have been used to frame position descriptions since the first

estimates of the earth's size were made by Aristotle.

Geodetic datums define the size and shape of the earth and the origin and orientation of

the co-ordinate systems used to map the earth.

Different datums might use

same reference ellipsoid.

Datum Differences


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Referencing geodetic co-ordinates to the wrong datum can result inposition errors of hundreds of meters.

Datum Differences

Survey report


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Survey report

System description

Site description and layout

Antenna and tower heights

Path profiles

System performance calculations

Frequency plans

Photographs

Checklist for survey of existing stations


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Checklist for survey of existing stations

Type of building. Concrete, wood, prefabricated shelter

Material used in ceiling, walls, floor

Measurements of rooms. Height of ceiling

Space fore new equipment in the equipment room

How to fix waveguide and cables to walls, ceilings

Waveguide outlets through walls etc.

New air dryer for waveguide necessary?

Available power. AC - DC

Existing battery capacity. New batteries necessary?

Can existing tower be used?

Distance from building to tower

How to lay the waveguide safely outside

Space for new antenna at the right height in the tower

Check of grounding system for the tower, station

Possible interface problems when connecting to existing equipment

Possible interference problems with existing equipment

Difficult areas for microwave links


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Difficult areas for microwave links

Overwater paths

Always difficult due to sea reflections. High reflection coefficient.

High possibility of ducting.

Swamps and rice fields

Can cause strong ground reflections.

High possibilitiy of multipath fading.

May look different at different times of the year. Rainy season, monsoon.

Desert areas

Can cause ground reflections. Sand does not have a high reflection coefficient.

High possibility of multipath fading due to temperature variations.

Hot and humid coastal areas

High degree of ducting probabilityArabian gulf, West africa, parts of the west indies and parts of the mediterranean.

Typical survey equipment


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Typical survey equipment

Maps (1:50 000)

Camera (digital)

Binoculars

Compass

Altimeter

Thermometer

Signalling mirrors

Tape measure

Satellite navigation

equipment (GPS)

Theodolite

Antenna horns

Low Noise Amplifier /Spectrum Analyser

Portable PC

Walkie-talkie or cellularphone (verify coverage)


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Error performance andavailability objectives

Chapter

Outline of ITU objectives


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Outline of ITU objectives

High grade

Medium grade

Class 1Class 2

Class 3

Class 4

Local grade

International portion

Terminating country

Intermediate country

National portion

Long haul section

Short haul section

Access section

G.821 G.826

Objectives conceptions


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Performance Availability / Unavailability

Equipment failure

Human activity (maintenance)

Outage due to rain

SES for for more than 10 consecutive sec.

SAvail = SObservation time - SUnavail

The connection is unavailable when:

As a rule of thumb:

Let 1/3 of total unavailability be occupiedby unavailability due to rain

Error performance should only be evaluatedwhilst the connection is in available state SAvail

SES (Severely Errored Second)

G.821 - bit error

1 sec. period with BER 10-3

G.826 - block error1 sec. period which contains 30% EBor at least one Severely DisturbedPeriod (AIS, LOS, LOF,.)

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

10 = SESRS

TSESR

Avail

SES

Scaling of the end-to-end objectives. G.821


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Localgrade

Mediumgrade

Highgrade

Mediumgrade

Localgrade

LE LET-reference

point

T-referencepoint

27 500km

1250 km 1250 km25 000 km

End-to-end, 27500km, error performance objectives is:

SES 0 2%.BER = 1 10 3

Local grade

* 15% block allowance to each

end of half of the total

allowance

Ex.:

SES

0 1% 15%0 015%..

Medium grade

Ex.:

High grade

* Each 2500km portion may contribute

not more than 0.004%

* Block allowance of 0.05% to a

2500km HRDP of radio relay system

Ex.:

( )SES +

0 004% 0 05%0 054%

. ..

L= 1200 km( )SES +

0 1% 15% 0 05%0 06 5%

. ..

* 15% block allowance to each end

of half of the total allowance

* Block allowance of 0.05% to a2500km HRDP of radio relay system

G.821

High Grade Objectives


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g j

Objectives for radio-relay systems

G.821

SES for no more than : [%]2500

054.0L

where 280km < L


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G.821

Performance for SES ITU-R Rec. F.696

Block allowance for each class

Availability / Unavailability ITU-R Rec. F.696

Block allowance for each class

j

Class 1 Class 2 Class 3 Class 40 < L < 280km 0 < L < 280km 0 < L < 50km 0 < L < 50km

0.006 % 0.0075 % 0.002 % 0.005 %

Class 1 Class 2 Class 3 Class 4

0 < L < 280km 0 < L < 280km 0 < L < 50km 0 < L < 50km

0.0033% 0.05 % 0.05 % 0.1 %

L is the system length

Local Grade Objectives


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j


G.821

SES for no more than: 0.015 % L < 50km

Performance ITU-R Rec. F.697-2

Block allowance.

Availability / Unavailability

Not yet defined by ITU

L is the system length

Performance objectives


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j

G.821G.821 G.826G.826

ITU-T Recommendation

IIR1-

Block-Based error Performance


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G.826

Errored block (EB)one ore more errored bits in a block.

Errored second (ES)

one ore more errored blocks in one second period.

Severely errored second (SES)one second period with >30% errored blocks or at

least one severely disturbed period.SDP:

Loss Of Signal

Loss Of Frame

Alarm Indication Signal

High Order Path AIS

Low Order Path AIS

Loss of AU pointer

Loss of TU pointer

Background block error (BBE)one block with error, not a part of SES.

Error Performance Objective forHypothetical Reference Path (HRP)


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Hypothetical Reference Path (HRP)

End-to end error performance objectives

( ITU-T rec. G.826)

Rate Mbit/s 1.5 to 5 > 5 to 15 > 15 to 55 > 55 to 160 > 160 to 3500

Bits/ block 2000-8000 2000-8000 4000-20 000 6000-20 000 15 000-30 000

ESR 0.04 0.05 0.075 0.16

SESR 0.002 0.002 0.002 0.002 0.002

BBER 2104 *) 2104 2104 2104 104

*) For systems designed prior to 1996: 3x10-4

G.826

Scaling of the end-to-end objectives. G.826

End to end 27500km error performance objectives (R t Mb/ 1 5 t 3500) is:


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End-to-end, 27500km, error performance objectives (Rate Mb/s 1.5 to 3500) is:

SESR 0 2%.

Hypothetical Reference Path27 500 km

PEP = Path end point

International Portion NationalPortion

NationalPortion

TerminatingCountry

TerminatingCountry

Intermediate

Country Inter-Country(e.q. Path

carried over aSubmarine

Cable)PEP PEPIGIGIGIGIG

International Gateway

1%

National portion International portion

* 17.5% fixed block allowance

* Plus a distance based allocation which is

1% per 500km, where the actual system length

is rounded up to the nearest multiple of 500km

Ex.:

L=600km

( )SESR +

0 2% 17 5% 2%0 039%

. ..

* 1% for each terminating country

* 2% per intermediate country

* Plus a distance based allocation which is

1% per 500km, where the actual system lengthis rounded up to the nearest multiple of 500km

Ex.: Norway - Sweden- Denmark

L=1200km

{ } { } { } { }( )SESR Nor Sw e Den dist + + +

0 2% 1% 2% 1% 3%

0 014%

.

.

BER 5 10 5

G.826

International portionDigital radio-relay systems


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Error performance objectives for constant bit rate digital path at or above theprimary rate carried by radio-relay systems which may form part of the

international portion of a 27 500km hypothetical reference path

G.826

Digital radio-relay systems

Rec. ITU-R F.1092-11999

G.826 - all mediums

F.1092-1 - radio-relay system in international portion

International Portion of HRP


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G.826 - > F.1092

Performance

Block allowance:Intermediate country: 2% of total allowance

Terminating country: 1% of total allowance

+ Distance based allowance *: 1% per 500km of total allowance

* actual system distance is rounded

up to next multiple of 500km

Availability / Unavailability Not yet defined by ITU

International Portion of HRP


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Performance

G.826 - > F.1092

SESR: 0.2 (FL + BL) [%] for rate 1.5 to 160Mbit/s

Distance allocation factor: 50001.0R

L

L

F =

Block allocation factor:

Intermediate countries:

>


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Error performance objectives for real digital radio links used in theinternational portion of a 27 500km hypothetical reference path at or above

the primary rate

G.826

Digital radio relay systems

Rec. ITU-R F.13971999

G.826 - all mediums

F.1092-1 - radio-relay system in international portion

F.1397 - scaled down obj. from F.1092-1

International Portion of HRP, scaled down


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Performance

G.826 - > F.1397

SESR: 0.2 (FL + BL) LLink/LR [%] for rate 1.5 to 160Mbit/s

Distance allocation factor: 50001.0R

L

L

F =

LR is the rounded value of L rounded

up to nearest multiple of 500km

Block allocation factor:

Intermediate countries:

>


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Error performance objectives for constant bit rate digital path at or above theprimary rate carried by digital radio-relay systems which may form part or all

of the national portion of a 27 500 km hypothetical reference path

G.826

Digital radio relay systems

Rec. ITU-R F.1189-11999

G.826 - all mediums

F.1189-1 - radio-relay system in national portion

Basic sections of national portion of HRP


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Path

end-point

Local

exchange Note 1

International

gateway

Note 1 In dependence of the country network architecture, this centre may coincide with a primary centre (PC),

a secondary centre (SC) or a tertiary centre (TC) (see ITU-T Recommendation G.801).

G.826 - > F.1189

Access

C

Short haul

B

Long haul

A

PerformanceFixed block allowance 17.5% of total allowance

+ Distance based allowance 1% per 500km of total allowance

(Ex.2500km: 5*1%*0.2%=0.01%)

(Ex.17.5%*0.2%=0.035%)

Availability / Unavailability Not yet defined by ITU

National portion


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Performance

G.826 - > F.1189

Long haul section Z = A A = A1 + (LR/500) A1 = 1 - 2 %

Short haul section Z = B fixed block allocation onl B = 7.5 - 8.5 %

Access section Z = C fixed block allocation onl C = 7.5 - 8.5 %

SESR: 0.2 Z [%] for rate 1.5 to 3500Mbit/s

A1% + B% + C% shall not exceed 17.5% and B% + C% are in the range 15.5% to 16.5%.

LR is the rounded value of L rounded up to the nearest multiple of 500 km; where L is

the actual system length


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Antennas

Chapter

Antenna Gain


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Gain = 17.8 + 20 log ( D . f )

squared GHz

constants decibel m

where D

f

=

=

antenna diameter

frequency

where

=

=

=

aperture efficiency (typical 0.5 - 0.6)

aperture area

wavelength

Gain = 10 log

( . A . 4

)dBi

2

Gain[dBi]

Half Power Beam Width


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The angular width of the

main beam at the -3 dBpoints

3 dB = 35 . degreesD

= wavelengthwhere

D = antenna diameter

-3dB

RPE Comparison at 6 GHzTypical 3.0 m Antennas


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Super High XPerformance

High XPerformance

HighPerformance

StandardPerformance

Different Performance levels according to systemrequirements.

0 5 10 15 30 45 60 75 90 105120135150165180

Azimuth Degrees from Main Lobe

80

70

60

50

40

30

20

10

Antennadirectivity;

dBdownfromMain

Lobe

HIGH X PERFORMANCE

SUPER HIGH X PERFORMANCE

CROSS POLARIZATIONCROSS POLARIZATION

Mechanical stability


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Deflectionangle[deg]

Passive repeaters


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There are two basic types of passive repeaters:

- plane reflectors

- back-to-back antennas

Planereflector

Back-to-backantennas

Passive repeaters


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Link budget with passive repeaters

The free space loss is substituted by:

Planereflector

Back-to-backantennas

A A G AL fsA R fsB= + [dB]

A

A

B B

Path loss variations


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Path loss with 6 m reflector2

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45

1

3

57

9

11

13

15

17

19

21

23

25

27

29

31

33

35

37

39

41

43

45

195-200

190-195

185-190

180-185

175-180

170-175

165-170

160-165

155-160

150-155

145-150

140-145

135-140

130-135

Path loss [dB]

Distanceleg 1 [km]

Distanceleg 2 [km]

Good:

Good:

Poor:

Gain of plane reflector


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[dB])

2

cos5.139log(20 2

= RR AfG

Reflectorgain[dB]

Gain of back-to-back antennas


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The gain of back-to-back antennas are given by:

G G A G R A c A= +1 2

GA1

GA2

Ac

[dB]


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Power budget

Chapter

Rx

Free Space Loss

Sphere


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P is radiated energy in A

Radiated energy through the sphere is P

Free space loss: 92.45 + 20 log (d. f) dB

Constants( etc.)

decibel km

GHzsquared

Radiated energy pr. unit area is P1 ~P

4d 2

1f 2 2Received energy in B P1 ~ d

Received energy in B is P1 ~Pd

2

B

Isotropic radiation

d

A

Maximum radiated energy from a point source ~ (Maxwell)1f2

Atmospheric attenuation


75/202


Specific attenuation due to atmospheric

gases P=1013 hPa T=15C rho=7.5 g/m3

0.001

0.01

0.1

1

15 20 25 30 35 40 45 50

Frequency [GHz]

S

pecificattenuation[dB/km]

dry air

w ater vapour

dry air+w ater

vapour

][ dBdA aa =

Starts to contribute to the total attenuation above approximately 15GHz

Parameters in a:

Frequency

Temperature

Air pressure

Water vapour

Link Budget

AntennaAntenna


76/202


Transmitter

AntennaFeeder

Receiver

Antenna

Feeder Atmosphere

RXTX

Tx output power +30dBm

- Feeder loss -2dB

+ Antenna gain +38dB- Free space loss -144.5dB (6.7GHz, 60km)

- Atmospheric attenuation 0dB

+ Antenna gain +40dB

- Feeder loss -3dB= Rx level -41.5dBm

- Rx threshold -75dBm

= FADING MARGIN 33.5dBm

Why Fading Margin ?


77/202


Atmospherical disturbance

Level

Time

Atmospherical

disturbance

Fadin g margin

Receiver

Threshold

Outage

SIGNAL SPREAD....................................

Multipath Rain (10 GHz )


78/202


Precipitation

Chapter

Characteristics of precipitation


79/202


OROGRAPHIC

Forced uplift of moist air over high ground

Dewpoint

Cloud withlittle watercontentPrevailing

wind direction

BERGENOSLO

Moist airis forced up .....

..........

..........

..........

.....

Convectional


80/202


Builds up in the afternoondue to convection of

hot humid air.

Anvil head

Strongverticalwind

A hotsummersday

May giveintense rain(hail) + thunder

...............

..........

..............

.

Cyclonic


81/202


Large scale vertical motions associated with synopticfeatures such as depressions and fronts.

Weather forecast: Rain, later showers

BERGEN

Stratiformlayer clouds

Connectivepillar clouds

Cold airCold air

Rain

. . . . .. . . . .. . . . .

. . . . .. . . . .

. . . . .. . . . .. . . . .

Rain

..........

..........

.....

..... ..........

Tropical Cyclone Storms(Hurricanes, Typhoons)


82/202


Moving circular storms

with intense convective

rain 50-200 km in diameter

MONSOON RAIN

Intense stratiform rain fall.

Several hours a day and extended over several hundreds

of kilometers.

Severedepression

Rain Measurements

TippingDrop


83/202


Typical raingauges

bucketcounter

Rainfall is measured in mm

Rain intensity is measured in mm/h (= amount/duration)

Integration time= time between readings

(1 min, 5 min, 10 min, hour, day)Example: a shower lasting 7 minutes

mm

30

20

10

1 minute minutes

1 min30, 90, 60, 30, 30, 30, 60 mm/h

5 min48, 18 mm/h

10 min33 mm/h

1 hour5.5 mm/h

Precipitation Intensity versus duration


84/202


20

15

10

5

00 10 20 30 40 50 60 70 80 90 100

0

1

2

3

4

5

6

7

8

Duration of storm (minutes)

Meanrainfall

intensity(cm/h)

Meanrainfallin

tensity(in/h)

The figure shows generalized relationship between precipitationintensity and duration for Washington, DC.

Source: Yarnell 1935

World record of precipitationThe figure shows the world record rainfalls and the envelope of


85/202


expected extremes at any place. The equation of the envelope lineis given, together with the state or country where each record wasestablished.

Rain cell size as a function of rain rate


86/202


Average rain cell size as a function of a rain rate

0

0 10 20 30 40 50 60 70 80 90 100

Rain rate, mm/h

Averageraincellsize,

km

110 120

1

2

3

4

5

Rain drop shape as function of size


87/202


Variation in the shape of water drops in air by size: (a) ao= 0.11 cm, (b) ao= 0.14 cm,(c) ao= 0.18 cm, (d) ao = 0.20 cm, (e) ao= 0.25 cm, (f ) ao= 0.29 cm, (g) ao= 0.30 cm,

(h) ao= 0.35 cm, (i) ao= 0.40 cm (from [Pruppacher and Pitter, 1971]).

Due to theshape of the

falling raindropthe verticalpolarization hasthe least spread(attenuation)

Drop size versus intensity


88/202


Per cent of total volume contributed by drops of various sizes forthree rainfall-rates, as computed for 0.25 mm intervals of diameter

Law, Parsons

Precipitation (Rain, snow, sleet, ice particles, hail)


89/202


The energy is attenuated due to

reradiation (scatter)

absorption (heating)

For wavelengths long compared with drop size:attenuation due to scatter > attenuation due to absorption.

For wavelength short in relation to drop size:attenuation due to absorption > attenuation due to scatter.

For wavelengths long compared with drop size:attenuation due to scatter > attenuation due to absorption.

For wavelength short in relation to drop size:attenuation due to absorption > attenuation due to scatter.

Microwave absorption in water

Under water experiment


90/202


P = P o e-z 1 cm -1 Attenuation log = 4.3dB/cm

1e

Under water experiment

Specific rain attenuation


91/202


= k R

These parameters vary withfrequency and polarization

R is the rain intensity in mm/h for 0.01 % of the time

r

The rain rate R is connected to the drop size distribution and terminal velocity of the raindrops. Knowing R it is possible to calculate the amount of rain drops and the size withinthe Fresnel zone.

Specific attenuation is given by

[dB/km]

Rain intensity for0.01% of the time


92/202


0.01 % 52.56 minutes

(1 minute integration time)

Rainfall contours for 0.01% of the timeAsia and Australia

The k and

1

Frequency(GHz)

0.0000387

kH

0.0000352

kv

0.912

H

0.880

v


93/202


124678

1012

1520253035404550

60708090

100120150200

300400

0.00003870.0001540.0006500.001750.003010.004540.01010.0188

0.03670.07510.1240.1870.2630.3500.4420.536

0.7070.8510.9751.061.121.181.311.45

1.361.32

0.00003520.0001380.0005910.001550.002650.003950.008870.0168

0.03350.06910.1130.1670.2330.3100.3930.479

0.6420.7840.9060.9991.061.131.271.42

1.351.31

0.9120.9631.1211.3081.3321.3271.2761.217

1.1541.0991.0611.0210.9790.9390.9030.873

0.8260.7930.7690.7530.7430.7310.7100.689

0.6880.683

0.8800.9231.0751.2651.3121.3101.2641.200

1.1281.0651.0301.0000.9630.9290.8970.868

0.8240.7930.7690.7540.7440.7320.7110.690

0.6890.684

Vertical polarization least attenuated.This is due to the shape of the falling rain drops.

Rain attenuation as a function offrequency and rain rate


94/202


Sp

ecificattenuation

[dB/km]

Effective path length


95/202


Since rain has a tendency to cluster (especially at high rain rates), onlyparts of a typical radio link path will be affected by rain. The effective pathlength containing rain cells is given by

+

=

Re

d

d

015.0351

where dis the path length in km

Ris the rain intensity in mm/h (integration time 1 minute).

for mm/h100:mm/h100 => RR

Effective path length


96/202


Effectiv

epathlength[km]

Fade depth due to rain

Attenuation due to rain in 0 01% of time may be found from:


97/202


( )( ) [%]10 /12.0log172.029812.0546.0628.11 %01.0 FArainP++=

[dB]%01.0 rA =

[dB]12.0)log043.0546.0(

%01.010 rainP

rainPAF+=

This formula scales to otherpercentages of time than 0.01%

Unavailability due to rain, Prain, for a path with fade margin, F

Attenuation due to rain in 0.01% of time may be found from:

The unavailability may be found by solving the equation above with respect to Prain

To avoid imaginary values, use r/ F = 0.155in case where r/ F < 0.154023.

25

Usable path lengths 155 Mb/s 18 GHz

P th l th

SDH typical path performance


98/202


20 40 60 80 100 120 1400

5

10

15

20

25

Path

length[k

m]

20 40 60 80 100 120 140

Rain rate [mm/h]

1.2m V1.2m H

0.6m V

0.6m H

Antenna , polarizationPath lengthlimited by outagedue to rain

1/3 of totalunavailabilityobjective

Path lengthlimited by outagedue to rain

1/3 of totalunavailabilityobjective

System gain(B - B):96.0 dBBranching loss:3.6 dB

System gain(B - B):96.0 dBBranching loss:3.6 dB

Chapter


99/202


Performance predictions


100/202


Prediction methods forterrestrial line-of-sight systems

ITU-R P.530-7

1997

P.530-7

Planning methods


101/202


ITU-R PN.530-7 gives prediction methods forcalculation of worst month outage probability.

The methods are derived from fading data paths

with lengths 7 - 95 km, frequencies 2 - 37 GHz,path inclinations 0 - 24 mrad and grazing anglesin the range 1 - 12 mrad.

Checked up to 273 km and down to 500 MHz.

ITU-R PN.530-7 gives prediction methods forcalculation of worst month outage probability.

The methods are derived from fading data pathswith lengths 7 - 95 km, frequencies 2 - 37 GHz,path inclinations 0 - 24 mrad and grazing anglesin the range 1 - 12 mrad.

Checked up to 273 km and down to 500 MHz.

P.530-7

Multipath fading

Fading due to layering of the atmosphere is the dominating factor of


102/202


( )

++

++= usedisdiversityifXP

1.330.75

ds

0.75

dns

XPsnstotPPP

PPPP

wherePns - non-selective (flat) outageP

dns

- non-selective outage with diversityPs - selective outagePds - selective outage with diversityPXP - outage due to clear-air cross-polarization for co-channel systems

g y g p gdegradation of radio-relays.

Non-selective or flat fading

Selective fading

Outage due to clear-air cross-polarization for system co-channel

P.530-7

Flat fading

[%]10 10F

PP


103/202


K - Geoclimatic factor

d - Path length (km)

f - Frequency (GHz)

: Path inclination (millirad)

[%]10 100ns PP =

4.189.06.3

0 )1(+= pfdKP

p

d

hhp

21 =

Fading occurrence factor:

P.530-7

Terrain height less than 100mabove mean sea level

Inland

Classification of path types


104/202


Large size of water:

English Channel, theNorth Sea, the larger

reaches of the Baltic andMediterranean Sea,Hudson Strait, and other

bodies of similar size or

larger.

Medium size of water:The Bay of Fundy (east

coast of Canada) and theStrait of Georgia (westcoast of Canada), the

Gulf of Finland, and

other bodies of similar

size.

Terrain height 100m

above mean sea level

Distance > 0 km

Distance > 50 km

Entire path profile

above 100m altitude

Distance > 0 km

Inland

Inland

Distance < 50 km

Terrain height

less than 100mabove mean sea

level

Costal, medium

or large size of

water

P.530-7

Inland paths

( )LL t CCCPK 01.0517 101005


105/202


where

C0

- type of terrain and lower antenna altitude

CLat

- path latitude

CLon

- path longitude

PL

- percentage of time refractivity gradient ( ) 100 N km

( )LonLat CCCLPK = 0

1.05.17 10100.5

P.530-7

Coastal paths

Medium sized water: Large water:


106/202


( )K

r K r K c i c cm= +10 1 log log for K Kcm i

K Ki= for K Kcm i

=

26.0for16921.01

26.0for19746.012034.12

2170.22

nsns

nsnsw

kk

kkr

100

12

nssd

ns

PI

k

=

The square of the non-selective correlation coefficient, kns:

( )

++++=

usedisdiversityifXP1.330.75

ds

0.75

dns

XPsns

totPPP

PPPP

The total outage due to multipath fading is calculated from :

Pns is the outage due to the non-selective component

is the fading activity factor

Distance [km]

80

Space diversity

low land


124/202


65

70

75

0 5 10 15 20 25

Vertical antenna separation [m]

Pat

hlength[km]

low landPL=10 %

7.5 GHz3.0m antennas

low landPL=10 %7.5 GHz3.0m antennas

Frequency diversity

1 1

2 2


125/202


2 2

Combinedchannels

Combinedchannels

Frequency diversity

{ }51080 10

= fdF

fd Iff

dfI


126/202


f - frequency spacing between rf-channels in GHz

f - carrier frequency in GHzd - distance in kmF - fading margin in dB

1.7 GHz < f < 13 GHz20 km < d < 75 km

f/f < 0.05

P.530-7

Frequency diversity

G Calculate non-selective outages :

[%]fd

nsdns

I

PP = Pns is the outage due to the non-selective component


127/202


P.530-7

fd

G Calculate selective outages :

( )22

1100 s

sds

k

PP

=

Ps is the non-protected selective outage

wherethe selective correlation coefficient, ks, is calculated from:

( )

( )

>


128/202


P.530-7

( )( )

>

=

26.0for16921.01

26.0for19746.012034.12

nsns

nsnsw

kk

kkr

The square of the non-selective correlation coefficient, kns:



( )

++++=

usedisdiversityifXP1.330.75

ds

0.75

dns

XPsns

totPPP

PPPP

The total outage due to multipath fading is calculated from :

100

1

2

nsfd

ns

PI

k

=

Frequency diversity improvement

64

66

68

Branching loss included

Branching loss included


129/202


50

52

54

56

58

60

62

64

1+1 2+1 3+1 4+1 5+1 6+1 7+1

Pa

thdistance[km]

g

Combined diversity, 4 receivers

Using frequency and space diversity at the same time


130/202


fdsd

nsdns

II

P

P +=



fdsd

s

ds II

PP

+=


Ps is the non-protected selective outage

NOTE: This method differs from the method describedin ITU-R rec. 530-7

P.530-7

Hybrid diversity, 2 receivers

An arrangement where a 1+1 system has two antennas at one of the radio sites only

1


131/202




2

1

2

1

2

1

2

P.530-7

sd

ns

dns I

P

P =

Hybrid diversity, 2 receivers


( )22

1100 s

sds

k

PP

=




132/202


wherethe selective correlation coefficient, ks, is calculated from:

( )

( )

>

=

26.0for16921.01

26.0for19746.012034.12

2170.22

nsns

nsnsw

kk

kkr

where the correlation coefficient, rw, of the relative amplitudes is given by:

The non-selective correlation coefficient, kns:

fnssnsns kkk ,, =P.530-7

System configuration 1+0


133/202


A B

C

C

BA



134/202




135/202


Hot standby configuration


136/202


Hot standby configuration


137/202


Chapter


138/202


Cross-polar interference

Double transmission capacity bycrosspolar co-channel operation

Vertical

1.24 Gbit/s - 8 x STM-1 Alternated Polarization


139/202


Horisontal

1 2 3 4 5 6 7 8 1' 2' 3' 4' 5' 6' 7' 8'

Vertical

Horisontal

1 2 3 4 5 6 7 8 1' 2' 3' 4' 5' 6' 7' 8'

2.48 Gbit/s - 16 x STM-1 Co-Channel Operation

28MHz

N+1 protection switching

2x(N+1) protection switching

Co-Channel Transmission

MODSTM-1 TX f I(v)Vertical

Polarisation

RX ATDE + DET STM-1


140/202


Realised with 4D-128TCM

XPIC improvement factor > 25 dB

MODSTM-1 TX f I(H)

Polarisation

HorizontalPolarisation

RX

XPIC

XPIC

ATDE + DET STM-1

LO

Depolarization mechanisms


141/202


U a reflected component of the co-polarised signal due to scattering or reflection from landor water surfaces

U a reflected component of the co-polarised signal due to reflection from an atmospheric layer

U a direct component of the signal due to refractive bending in the atmosphere

U the direct co-polarised signal by tropospherical turbulence.

Depolarization of :

Reduced interference with ATPC


142/202



143/202

Outage due to reduction of XPD

Prediction of outage due to clear-air effects

( ) ++

= 1 33XPsns PPP

P


144/202


Prediction of outage due to precipitation effects

( )

++

=usedisdiversityifXP

1.330.75

ds

0.75

dns

totPPP

P

=

XPDrainXPR

XPDrainrain

totRainPPP

PPPP

if

if,

The total outage probability due to rain is calculated from taking thelargest value of Prainand PXPR.

P.530-7

Prediction of outagedue to clear-air effects

1 4XPDXPD XPD

XPD

g g

g0

5 35

40 35=

+

>

for

for C XPD Q= +0


145/202


2

3

5( ) = 1 0 20

0 75

e P..

Qk

P

xp=

10

0

log

where

k sxp t=

0 7

1 0 3 4 10 62

.

. exp

one transmit antenna

two transmit antennas

P Pxp

MXPD

= 0 1010

M

CC

I

CC

IXPIF

XPD =

+

0

0

without XP IC

with XP IC

where

Prediction of outagedue to precipitation effects

1 4 ( )( )ApU C I XPIF V = +10 0/ / SetXPIF=0

if no XPIC is usedU U f= +0 30log

U a ve r a g e0 1 5( ) d B


146/202


2

3

( )( )m A A mp=

23 26 0 12 40

40

0 01. log . . if

otherwise

( )

PXPRn

=

10

2Determine the path attenuation

exceeded for 0.01% of the time

( )n m= + 12 7 161 23 4 2. .

g0 ( )

U m in i m u m0

9( ) d B

C-pol

6.77

1529

40.3

2.3

0

67

132.5

Quarter

Head

X-pol

6.77

1529

40.3

2.3

30

37

132.5

Down ->

C-pol

6.77

1229

40.3

2.5

0

66.8

130.6

Head

X-pol

6.77

1229

40.3

2.5

30

36.8

130.6

Power ->

C-pol

6.77

3829

43.6

3

0

69.6

140.6

Head

X-pol

6.77

3829

43.6

3

30

39.6

140.6

Train ->

C-pol

6.77

4229

43.6

3

55

14.6

141.5

High

X-pol

6.77

4229

43.6

3

62

7.6

141.5


184/202


( )( ) ( )( )( ) dBm9.94101log101475101log10 10/757410/ =++=++< TeTeI LLRTeI CLLWith 1 dB threshold degradation mustL

Ibe less than -94.9dBm :

Rx input level (nom)

Antenna Gain Rx

Losses Rx

Dir. discr. Rx(pol)

Interference levelS/I (no fading)

Threshold 1E-3

Threshold 1E-6

S/I BER 1E-3

S/I BER 1E-6

dBm

dB

dB

dB

dBmdB

dBm

dBm

dB

dB

-32.9

43.6

3.1

46

-71.038.1

-73

-69

-2.0

2.0

-32.9

43.6

3.1

53

-78.045.1

-73

-69

5.0

9.0

-32.9

43.6

3.1

46

-69.336.4

-73

-69

-3.7

0.3

-32.9

43.6

3.1

53

-76.343.4

-73

-69

3.3

7.3

-32.9

43.6

3.1

55

-85.552.6

-73

-69

12.5

16.5

-32.9

43.6

3.1

62

-92.559.6

-73

-69

19.5

23.5

-32.9

43.6

3.1

0

-86.453.5

-73

-69

13.4

17.4

-32.9

43.6

3.1

30

-93.460.5

-73

-69

20.4

24.4

Countermeasures

New radio-channels:

Hill Headquarter - DowntownTraining centre - Mt. High

Reduced output power:HeadquarterDowntown

Hill

Power station

1,3 H

2,4 H

2,4V


185/202


Hill Headquarter - Downtown

HP antennas in nodal point:

Headquarter

Changed polarization:

Power station - HeadquarterHill Headquarter - Downtown

Downtown

Training centre

Mt. High

A-station

B-station

1,3H

2,4H

The Frequency Plan

Power

station

Training

centre

Training

centre

1,3H

1', 3'

1,3V

1', 3'

2,4V

2', 4'


186/202


Head-

quarter

Hill Down-town

2,4V

2',4'

2,4H

2',4'

Reduced interference with ATPC

A B


187/202


without ATPC on B

with ATPC on B

without ATPC on A

with ATPC on A

Increased capacity with ATPC

155Mb/s 7.5GHz

Co-channel operation

ATPC dynamic = 15dB

3.0m SHXP antennas

Required S/N with ATPC = 50dB

Example


188/202


qRequired S/N without ATPC = 65dB

Same polarization Opposite polarization

15

67

59

With ATPCWithout ATPC

With ATPC

Without ATPC

Antenna radiation patterns

-20

-10

0 dB

GAIN * : 39.8 dB 0.23 dB BEAMW IDTH: 0.85VSWR 1.08

* At center frequency

HORIZONTAL POLVERTICAL POL

CROSS POL

RADIATION PATTERN ENVELOPE

ANTENNA TYPE: HIGH PERF ORMANCEFREQUENCY : 6.425 - 7.125 GHzDIAMETER : 2.0 m

-20

-10

0 dB

GAIN * : 43.0 dB 0.23 dB BEAMWIDTH: 0.55VSWR 1.08

* At center frequency

RADIATION PATTERN ENVELOPE

ANTENNA TYPE: HIGH PERFORMANCEFREQUENCY : 6.425 - 7.125 GHz

DIAMETER : 3.0 m

HOR. OR VER. POL

CROSS POL


189/202


15 30 45 60 75 90 105120 135 150 165180

-80

-70

-60

-50

-40

-30

0 5 10

CROSS POL

15 30 45 60 75 90 105 120 135 150 165180

-80

-70

-60

-50

-40

-30

0 5 10

Antenna radiation patterns


190/202


Threshold-to-Interference versusFrequency

T/I versus Frequency separation NL29x - 155MB/s - 128TCM

10

20

30

40

ence[dB

]

< 1 dB threshold degradation


BER=1E-3

T/I versus Frequency separation NL29x - 155MB/s - 64TCM

5

15

25

35

ence[dB

]



BER=1E-3


191/202


-40

-30

-20

-10

0

-55 -45 -35 -25 -15 -5 5 15 25 35 45 55

Frequency offset [MHz]

Threshold-to-Interfere

Band width of interferes source

is the same as the band width

of the radio 28MHz.

-45

-35

-25

-15

-5

-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Frequency offset [MHz]

Threshold-to-Interfere

Band width of interferes source

is the same as the band widthof the radio 40MHz.

Chapter


192/202


Reliability

Reliability Failure Probability

Initialfailure

s

Probability

offailure

The probability that electronic equipment fails in service is not constant with time.


193/202


Useful lifetime timeWear-outperiod

Burn-inperiod

Random failuresWea

r-out

failu

res

During the time called the useful lifetime, the failure rate are random and theequipment reliability can be predicted using analytical methods.

Equipment Failure Rate

After the burn-in period, the equipment failure rate is constantuntil the wear-out period starts.

If the failure rate per unit time equals , the average timebetween failures is given by

11 == tt


194/202


tis called MTBF(Mean Time Between Failures).

MTBF is more convenient to use than when calculatingunavailability.

1

[hour]MTBF=

Definition of Availability andUnavailability

The MTBFof a system can be predicted from reliability analysis. The mean time to restore,

MTTR, must be assessed taking maintenance policy and accessibility into account

Availability

Unavailability

MTTRMTBF

MTBFA

+=


195/202


y

MTTRMTBF

MTTRN

+=

The relation between A and Nis as follows

AN = 1

MTBF

MTTRN

For telecommunication systems MTBF >> MTTR, and unavailability can be approximated to

Calculation of Unavailability

Unavailability of one equipment module

N

MTTRMTBF

MTTR

N +=


196/202


Transmitter group 140 Mb/s - 64 QAM

MTBF = 125000 hours

MTTR= 10 hours

Example

5108000125

10

10000125

10 =+

=N

N1 N2 N3 Nn

Ns

Availability of the total system

The system will be available only if all the modules are available simultaneously.

Unavailability of cascaded modules


197/202


( )==

==n

i

i

n

i

is NAA

11

1

( ) = ==

=

==

n

i

n

i

i

n

i

iiss NNNAN1 11

11111

The unavailability of a cascaded module is the sum of unavailabilityof its individual modules

Unavailability of parallel modules

N1

N2

Ni


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Ns

The system will be unavailable onlyif all the modules are unavailable.

=

=n

i

is NN

1

Unavailability of a n+1 Redundant System

A protected channel is unavailable if two (more than two channelsunavailable is assumed very little) of the unprotected channels areunavailable

The unavailability ofthe unprotectedchannels are all N.

N2

N3

Nn

N1

nprotectedchannels

n+1 unprotected channels


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unavailable.

The unavailability of one protected channel in a n+1 system is given by

( )( )( )

( )( ) 2121 1!21!2

!11 ++

++= nn NN

nn

nN

Twofailing

All othersnot failing

Unavailability ofone channel only

2

12

1N

nNn

++

22

13 22

13NNN =

++

Example

Summary of Unavailability calculationsIf MTTR(Mean Time To Restore) is common for all modules is itconvenient to use failure rate

1 2 3 n

Ns

Cascadedmodules

( )nSS MTTRMTTRN ++== 321


200/202


( )nSS MTTRMTTRN == 21

NS

1

Parallelmodules

2

n

Cableequalizer

Modulator XMTR

XMTR

RCVR

RCVR

Demod

Demod RCVRDistr.

Relayunit

XMTRswitch

Modulator

Example: NL190 64QAM 140 Mb/s


201/202


Module MTBF Failure rate,Cable equalizer 830 000 hours 1.210

-6

Modulator 375 000 hours 2.710-6

Transmitter 290 000 hours 3.510-6

Receiver 200 000 hours 5.010-6

Demodulator 315 000 hours 3.210-6

Relay unit 3 300 000 hours 0.310-6

Transmitter switch 555 000 hours 1.810-6

Receiver distribution unit 830 000 hours 1.210-6

Simplified block diagram of NL190

( ) 661 104.14102.30.55.37.2 =+++=r

( ) 662 104.17102.12.30.55.37.28.1 =+++++=r

( ) 66 105.1103.02.1 =+=c

Example: Equipment UnavailabilityThe failure rates for the two redundant paths are

The failure rate for common units:

Mean time to repair MTTR=3 hours for all units.

Unavailabilityr1


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5

11 1032.4= rr MTTRN

5

22 1022.5= rr MTTRN

( ) ( )( ) 62121 1050226.4=+=+= rrcrrce MTTRNNNN

min /year)4.5(or10926== ep NN

y

6105.4 = cc MTTRN

The equipment unavailability is thus

The path unavailability and availability are

99.9991%)(or999991.01 == pp NA

Cableequalizer

Modulator XMTR

XMTR

RCVR

RCVR

Demod

DemodRCVRDistr.

Relayunit

XMTRswitch

Modulator

r2

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