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ERA/LN-97:1957 1997-10-10 Rev PA1
ERA/LN-97:1957 1997-10-10 Rev PA1
ITU RecommendationsITU Recommendations
ITU Recommendation on the Intranet:
http://krus.lme.ericsson.se/itu/itupage.htm
ERA/LN-97:1957 1997-10-10 Rev PA1
General ConfigurationGeneral Configuration
Radio
Radio
Radio
Radio
Wave guideloss
Branchingloss
Antennagain
Outputpower
Free space loss+ Additional losses
ERA/LN-97:1957 1997-10-10 Rev PA1
Link BudgetLink Budget
Feederloss
Antennagain
Free space loss +Additional losses
Branchingloss
Outputpower
Antennagain
Branchingloss
Feederloss
Receivedpower
Receiverthreshold
Fadingmargin
Additional losses:- Gas absorption- Obstacle loss
P.341
ERA/LN-97:1957 1997-10-10 Rev PA1
Fading MarginFading Margin
Receivedpower
Receiverthreshold
Fadingmargin
Fading margin:“Safety” margin. Should belarge enough to guaranteethat quality and availabilityobjectives are met duringfading conditions.Typical value ~ 40 dB
ERA/LN-97:1957 1997-10-10 Rev PA1
FadingFading
Fading
Flatfading
Frequencyselective fading
Multipath fading Rain fading
ERA/LN-97:1957 1997-10-10 Rev PA1
Free space lossGas absorption
Hop CalculationsHop CalculationsPredictable Statistically Predictable
Obstacle loss
Always presentand predictable
Predictableif present
Not always presentbut statisticallypredictable
Rain fadingMultipath fading
Link Budget Fading Prediction
Q&A Objectives
ERA/LN-97:1957 1997-10-10 Rev PA1
Free Space LossFree Space Loss
Afs = 92.4 + 20 log d + 20 log f
d: distance [km]f: frequency [GHz]
P.525
ERA/LN-97:1957 1997-10-10 Rev PA1
Link Budget, ExerciseLink Budget, Exercise
1) Calculate the fading margin for a 7 km MINI-LINK 15-E hop with 4x2 Mbit/s capacity, standard output power and 0.6 m antenna.
2) Calculate the fading margin for a 7 km MINI-LINK 15-E hop with 4x2 Mbit/s capacity, high output power and 1.2 m antenna.
3) Calculate the fading margin for a 5 km MINI-LINK 23-E hop with 2x8 Mbit/s capacity and 0.3 m antenna.
Assume a feeder loss of 0.5 dB and no branching loss.
ERA/LN-97:1957 1997-10-10 Rev PA1
Link Budget, ExerciseLink Budget, Exercise
threshrx
fsfeederanttxrx
LLM
AAGLL
22
ERA/LN-97:1957 1997-10-10 Rev PA1
Link Budget, ExerciseLink Budget, Exercise
1) Standard output power = Ltx = 18 dBm Rec. threshold 10-3 = Lthresh = -87 dBm Rec. threshold 10-6 = Lthresh = -83 dBm Antenna gain = Gant = 36 dBi
8.43)7log2015log204.92(
5.0236218
Lrx
dBm
2.43)87(8.43310 threshrx LLM dB
2.39)83(8.43610 threshrx LLM dB
ERA/LN-97:1957 1997-10-10 Rev PA1
Link Budget, ExerciseLink Budget, Exercise
2) High output power = Ltx = 25 dBm Rec. threshold 10-3 = Lthresh = -87 dBm Rec. threshold 10-6 = Lthresh = -83 dBm Antenna gain = Gant = 42 dBi
2.62)87(8.24310 M
2.58)83(8.24610 M
dB
dB
ERA/LN-97:1957 1997-10-10 Rev PA1
Link Budget, ExerciseLink Budget, Exercise
1) Standard output power = Ltx = 20 dBm Rec. threshold 10-3 = Lthresh = -83 dBm Rec. threshold 10-6 = Lthresh = -79 dBm Antenna gain = Gant = 35 dBi
4.38)83(6.44310 M
4.34)79(6.44610 M
dB
dB
ERA/LN-97:1957 1997-10-10 Rev PA1
Gas AbsorptionGas Absorption
Gas Absorption
Oxygen Water vapour
Should be considered for f > 10 GHz.
: Specific attenuation for dry air [dB/km]
: Specific attenuation for water vapour [dB/km]
where
dgasgasA
wairgas
air
P.530
P.676
P.836
ERA/LN-97:1957 1997-10-10 Rev PA1
Gas Absorption, contd.Gas Absorption, contd.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20 25 30 35 40 45 50
Frequency, GHz
Sp
ecif
ic g
as a
tten
uat
ion
, d
B/k
m
Oxygen Water Vapour Total
T = 15° C, Water vapour density = 20 g/m3
ERA/LN-97:1957 1997-10-10 Rev PA1
Refractive IndexRefractive Index
n1
n2
nicvi
n n1 1 2 2 sin sin
ERA/LN-97:1957 1997-10-10 Rev PA1
RefractivityRefractivity
Refractivity: N n ( )1 106
Empirical formula:
NT
pe
T
77 64810
.
T: Temperature [Kelvin]p: Total air pressure in [hPa]e: Water vapour pressure [hPa]
P.453
ERA/LN-97:1957 1997-10-10 Rev PA1
Refractivity GradientRefractivity Gradient
Since p, e and T are functions ofheight N is also a function of height.
For normal atmosphere:
dN
dh 40
N units
km
P.453
P.310
ERA/LN-97:1957 1997-10-10 Rev PA1
Ray bendingRay bending
The radio beam is bent in the atmosphere,normally slightly downwards.
The k factor is a function of the refrectivitygradient.
For design purposes, the bending effect iscompensated by introducing a correction factor k.
P.834
ERA/LN-97:1957 1997-10-10 Rev PA1
Ray Bending, contd.Ray Bending, contd.
k=-2/34/312/3
Tra
nsm
itter
Rec
eive
r
ERA/LN-97:1957 1997-10-10 Rev PA1
The k-factorThe k-factor
kdN
dh
157
157
For normal atmosphere:
dN
dh 40 k
4
3
ERA/LN-97:1957 1997-10-10 Rev PA1
The k-factor, contd.The k-factor, contd.
True ray beamOptical line-of-sight
True earth
r
ERA/LN-97:1957 1997-10-10 Rev PA1
The k-factor, contd.The k-factor, contd.
Effective ray beam
Optical line-of-sight
Effective earth
rkre
ERA/LN-97:1957 1997-10-10 Rev PA1
Earth BulgeEarth Bulge
h
d1 d2
h
kdd
h
74.12
21 h [m]d [km]
ERA/LN-97:1957 1997-10-10 Rev PA1
The Fresnel ZoneThe Fresnel Zone
The radiated power is distributed in azone surrounding the direct line-of-sight.
ERA/LN-97:1957 1997-10-10 Rev PA1
The Fresnel Zone, contd.The Fresnel Zone, contd.
d d d3 4 2 /
d
d1 d2
d3 d4
rf
rd d
f df
17 3 1 2.
d [km], rf [m], f [GHz]
Def:
P.526
ERA/LN-97:1957 1997-10-10 Rev PA1
Design objective:Full clearance of the Fresnel zone.
Ok!
The Fresnel Zone, contd.The Fresnel Zone, contd.
ERA/LN-97:1957 1997-10-10 Rev PA1
The Fresnel Zone, ExerciseThe Fresnel Zone, Exercise
f = 15 GHzk = 4/3d = 20 km
1) Calculate the Fresnel zone radius at mid path.
2) Calculate the earth bulge at mid path.
f = 15 GHzk = 4/3d = 10 km
ERA/LN-97:1957 1997-10-10 Rev PA1
The Fresnel Zone, ExerciseThe Fresnel Zone, Exercise
20 km:r m
17 310 10
15 2010.
h m
10 10 3
12 74 46
.
10 km: r m
17 35 5
15 107.
h m
5 5 3
12 74 415
..
ERA/LN-97:1957 1997-10-10 Rev PA1
Calculation of Antenna HeightsCalculation of Antenna Heights
Bh
d
GAh
Ahdd
k
ddd
obsthrd
GBh
1
))(1
(74.12
)1
(1
hGA, hGB Height above ground for antenna [m]hA, hB Height above sea level [m]hobst Height above sea level for highest
obstacle [m]d Distance A to B [m]d1 Distance A to obstacle [km]k Effective earth radius factor
ERA/LN-97:1957 1997-10-10 Rev PA1
Calculation of Antenna Heights. contd.Calculation of Antenna Heights. contd.
r Required clearence above obstacle [m]where:
r Radius of the Fresnel zoner Required clearence above obstace [%]
100rr
r
r r
ERA/LN-97:1957 1997-10-10 Rev PA1
Obstacle LossObstacle Loss
Obstacle loss
Knife edgeobstacle loss
Smooth sphericalearth obstacle loss
ERA/LN-97:1957 1997-10-10 Rev PA1
Knife Edge ObstaclesKnife Edge Obstacles
ERA/LN-97:1957 1997-10-10 Rev PA1
Smooth Spherical Earth ObstaclesSmooth Spherical Earth Obstacles
ERA/LN-97:1957 1997-10-10 Rev PA1
Knife Edge LossKnife Edge Loss
From curve or approximate formula:
rh
v
vvA
los
obst
)212log(204.6 2
hlos
r
V > 0
V < 0
P.838
ERA/LN-97:1957 1997-10-10 Rev PA1
Knife Edge Loss, contd.Knife Edge Loss, contd.
0 0 6 12 20 dB
Typical losses:
ERA/LN-97:1957 1997-10-10 Rev PA1
Smooth Spherical Earth LossSmooth Spherical Earth Loss
d
dA dBdr hB
hA
AA hRkd 3102
R: True radius of the earth (=6370 km)
If k = 4/3 AA hd 1.4
P.838
ERA/LN-97:1957 1997-10-10 Rev PA1
Smooth Spherical Earth Loss, contd.Smooth Spherical Earth Loss, contd.
robst
BAr
dkfA
dddd
3/23112.020
)(
f [MHz]
ERA/LN-97:1957 1997-10-10 Rev PA1
Smooth Spherical Earth Loss, contd.Smooth Spherical Earth Loss, contd.
40
20
10
dB
Typical losses:
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain AttenuationRain Attenuation
Two types of attenuating mechanisms:absorption and scattering caused by the rain drops.
Falling raindrop
Not round dueto air resistance
Horizontally polarized waves are attenuatedmore than vertically polarized waves.
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Attenuation, contd.Rain Attenuation, contd.
Rain intensity [mm/h].
For the calculations the cumulative distributionof rain intensity, i.e. the percentage of timeduring which a given rain intensity is exceeded,is interesting.
The reference level is the rain intensity that isexceeded 0.01% of all time (R0.01).
ITU-R presents the cumulative distribution ofrain intensity for 15 different rain zones on earth.
P.837
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Attenuation, contd.Rain Attenuation, contd.
effdRRA
:R Specific rain attenuation [dB/km]
:effd Effective path length, km
P.530
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Attenuation, contd.Rain Attenuation, contd.
fRfkR
:, ffk Coefficients reflecting assumptionsconcerning the distribution of raindropsize, form, temperature and polarization.
P.838
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Attenuation, contd.Rain Attenuation, contd.
fkVVkHHkVVkHHk
f
VKHkVkHkfk
2
2cos2cos)(
2
2cos2cos)(
:,,, VVkHHk Frequency dependent coeff.,from table
::
The path elevation angle
The polarization tilt anglerelative to the horizontal plane
P.838
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Attenuation, contd.Rain Attenuation, contd.
01.0015.00
0
35
1
1
R
eff
ed
dd
r
rdd
d: Actual path lengthr: Reduction factor
The reduction factor transforms actual path lengthto equivalent path length along which the rain canbe regarded as having a uniform distribution.
P.530
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Attenuation, contd.Rain Attenuation, contd.
0
5
10
15
20
25
0 20 40 60 80 100
120
140
Rain intensity (R0.01), mm/h
Sp
ecif
ic r
ain
att
enu
atio
n,
dB
/km
23 GHz, H
23 GHz, V
15 GHz, H
15 GHz, V
7 GHz, H
7 GHz, V
H/V: Horizontal/Vertical polarisation
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain FadingRain Fading
The probability that a given fade marginis exceeded, on an annual basis:
M
A
rain
R
P
01.012.0log172.029812.0546.0628.11
10
:
:01.0
M
AR The rain attenuation exceeded 0.01 %of the time
Fade margin
P.530
ERA/LN-97:1957 1997-10-10 Rev PA1
Rain Fading, contd.Rain Fading, contd.
15.1
87.0
30.0
85.2
monthyear
yearmonth
PP
PP
Conversion between yearly values andworst month values:
Formulas based on climatic constants.
P.841
ERA/LN-97:1957 1997-10-10 Rev PA1
Multipath FadingMultipath Fading
Flatfading
Frequencyselective fading
Multipath fading
ERA/LN-97:1957 1997-10-10 Rev PA1
Multipath Fading, contd.Multipath Fading, contd.
Atmospheric layer
ERA/LN-97:1957 1997-10-10 Rev PA1
Multipath Fading, contd.Multipath Fading, contd.
A
fB
A
fB
Flat fading Frequencyselective fading
ERA/LN-97:1957 1997-10-10 Rev PA1
Flat FadingFlat Fading P.530
The probability that a given fade marginis exceeded, on a worst month basis:
104.189.06.3 10)1(M
flat fdKP
D: Path length [km]f: Frequency [GHz]: Path slope [mrad]M: Fade margin [dB]K: Geoclimatic factor
ERA/LN-97:1957 1997-10-10 Rev PA1
Flat Fading, contd.Flat Fading, contd.
d
hh BA
Path slope:
hA, hB: Antenna height + ground elevation [m]
ERA/LN-97:1957 1997-10-10 Rev PA1
Flat Fading, contd.Flat Fading, contd.
The geoclimatic factor K is a function of thePL factor. The PL factor is the percentage oftime that the average refractivity gradient at theearth surface is lower than -100 N-units/km.
PL factor estimates in the form of contour mapsavailable in ITU-R Rec. P.453.
P.453
ERA/LN-97:1957 1997-10-10 Rev PA1
Flat Fading, contd.Flat Fading, contd.
5.1)1.7(10 LCC PK LonLat
5.1)9.5(10 LCC PK LonLat
5.1)5.5(10 LCC PK LonLat
Overland with antennasless than 700 m abovemean sea level
5.1)5.6(10 LCC PK LonLat
Overland with antennasmore than 700 m abovemean sea level
Over medium-sizedbodies of water
Over large bodiesof water
ERA/LN-97:1957 1997-10-10 Rev PA1
Frequency Selective FadingFrequency Selective Fading F.1093
The prediction of frequency selective fadingis very difficult and there exists many differentprediction models.
r
m
B
WPsel
220103.4
ERA/LN-97:1957 1997-10-10 Rev PA1
Frequency Selective Fading, contd.Frequency Selective Fading, contd.
Probability of the occurrence of mp fading
4
3
02.01
Pe
P0 from the formula for flat fading
W Signature width [GHz]Equipment dependent
B Signature depth [dB]Equipment dependent
ERA/LN-97:1957 1997-10-10 Rev PA1
Frequency Selective Fading, contd.Frequency Selective Fading, contd.
m Mean value of the echo delay
5.1
0 50
d
mm
m0 is the mean relative delay for astandard path of 50 km [ns].Normally 0.7 ns.
d is the path length [km]
ERA/LN-97:1957 1997-10-10 Rev PA1
Frequency Selective Fading, contd.Frequency Selective Fading, contd.
r The time delay used during measurementsof the signature curves (reference delay)[ns]. Normally 6.3 ns.
ERA/LN-97:1957 1997-10-10 Rev PA1
DiversityDiversity
Primarely used to reduce the effects ofmultipath fading.
Diversity
SpaceDiversity
FrequencyDiversity
Requiresmorebandwidth
ERA/LN-97:1957 1997-10-10 Rev PA1
Space DiversitySpace Diversity
Tx Rx
Rx
s
Height
Field strength
Optimum antennaseparation
ERA/LN-97:1957 1997-10-10 Rev PA1
Space Diversity ImprovementSpace Diversity Improvement
I
PP
I
PP selflatmp
mpdiv
101001034.3
101
04.1048.012.087.04 GMP
dfs
eI
s Vertical separation between antennas [m]f Frequency [GHz]d Path length [km]M Fade margin [dB]G The difference in antenna gain between the
two antennas [dB]
P0 from theformula forflat fading
P.453
ERA/LN-97:1957 1997-10-10 Rev PA1
Space Diversity Improvement, contd.Space Diversity Improvement, contd.
2 GHz f 11 GHz
43 km d 240 km
3 m s 23 m
In cases where any of these boundaries havebeen exceeded (within reasonable limits) theparameters may be set equal to the boundaryvalue (E.g. for 15 GHz, use f = 11 GHz).
ERA/LN-97:1957 1997-10-10 Rev PA1
Hardware UnavailabilityHardware Unavailability
MTBFMTTR
MTTRMTBFMTTR
N
1
N1
Unavailability of one equipment module
ERA/LN-97:1957 1997-10-10 Rev PA1
Hardware Unavailability, contd.Hardware Unavailability, contd.
n
iis NN
1
N1
Unavailability of cascaded modules
N2 Ni
ERA/LN-97:1957 1997-10-10 Rev PA1
Hardware Unavailability, contd.Hardware Unavailability, contd.
Unavailability of parallel modules
N1
N2
Nn
n
iis NN
1
ERA/LN-97:1957 1997-10-10 Rev PA1
Hardware Unavailability, contd.Hardware Unavailability, contd.
SMU
MMU
MMU
RAU
RAU
SMU
MMU
MMU
RAU
RAU
22 RAUMMUSMUs NNNN
MINI-LINK 1+1 system:
ERA/LN-97:1957 1997-10-10 Rev PA1
Quality and Availability ObjectivesQuality and Availability Objectives
Unavailable time (UAT)A period of unavailable time begins when one or both ofthe following conditions occur for 10 consecutive seconds:1. The digital signal is interrupted,2. The bit error ratio in each second of the 10 consecutive seconds are worse than 110-3. These 10 seconds are considered to be unavailable time.
Available Time (AT)A period of available time begins with the first second ofa period of 10 consecutive seconds of which each secondhas a bit error ratio (BER) better than 110-3.
G.821
ERA/LN-97:1957 1997-10-10 Rev PA1
Q & A Objectives, contd.Q & A Objectives, contd. G.821
Errored Second (ES)Any second containing one or more errors.
Severely Errored Second (SES)An errored second with a bit error ratio (BER) worsethan 110-3.
Degraded Minutes (DM)Obtained by substracting severely errored seconds fromthe available time and collecting the remaining secondsinto groups of 60 seconds. Any group with a bit errorratio worse than 110-6 is considered a degraded minute.
ERA/LN-97:1957 1997-10-10 Rev PA1
Q & A Objectives, contd.Q & A Objectives, contd.
Time > 10 sTime< 10 s
DMES
SESES
DMES
DMES
DMES
AT UAT AT
PRx
BER 10-3
BER 10-6
ERA/LN-97:1957 1997-10-10 Rev PA1
25000 km 1250 km1250 km G. 821
SES 0.1 % +0.1 % forHRDP
DM 10 %
ES 8 %
0.015 0.015 0.04 0.015 0.015
Hypothetical Reference Connection - HRX 27500 km
1.5 1.5 4 1.5 1.5
1.2 1.2 3.2 1.2 1.2
0.05 0.052500 km0.004+0.05
2500 km0.4
2500 km0.32 INT LE
Local Medium High Medium Local
Q & A Objectives, contd.Q & A Objectives, contd. G.821
ERA/LN-97:1957 1997-10-10 Rev PA1
50 km280 km
SES 0.1 % +0.1 % for HRDPin Class 1 & 2(0.05 % per end)
DM 10 %
ES 8 %
0.006 = 0.0075 0.002 0.005
Hypothetical Reference Digital Section - HRDS 280 & 50 km
0.045 0.2 0.2 0.5
0.036 0.16 0.16 0.4
High Medium Medium Medium
Class 1 Class 2 Class 3 Class 4
0.45 % 2 % 2 % 5 % ITU-R Rec. 696
0.10.1% x % x 0.450.45 + + 0.050.05 x 280 / 2500 x 280 / 2500
Q & A Objectives, contd.Q & A Objectives, contd. F.696
0.033 0.05 0.05 0.1 UAT
ERA/LN-97:1957 1997-10-10 Rev PA1
Q & A Objectives, contd.Q & A Objectives, contd.
UAT: Rain Fading +Hardware Unavailability
DM: Rain Fading + Multipath Fading
ES: Rain Fading + Multipath Fading
SES: Multipath Fading
The relationships are not described by ITU!
ERA/LN-97:1957 1997-10-10 Rev PA1
Q & A Objectives, contd.Q & A Objectives, contd.
hwrain PPUAT 310
310310610610
mprainmprain PPPPDM
310 mpPSES
UATPPES mprain 610610