Rain Fading - Kizer - Rev B

7/30/2019 Rain Fading - Kizer - Rev B

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Update on MW Radio

Rain Fading EstimationGeorge Kizer


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Copyright 2010 Alcatel-Lucent. All rights reserved.

Major Topics

MW Path Design

Point Rain Attenuation

Point to Path Conversion Factor

Rain Fading Variability


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Rain Fading


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Microwave Path Design Parameters

North America Europe (ITU-R)

Quality (one way) Not Calculated Multipath(worst month) (tested) Short Term Interference

Availability (two way) Multipath Rain(annual) Rain Long Term Interference

Interference Hardware

Calculations are typical (median) estimates, not worst case.


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Microwave Path Rain Design

North America Europe (ITU-R)

Rice and Holmberg (ITS, 1973)*

Lin (Bell Labs, 1977)**

Crane (1980)* ITU-R P.530-1 (1978)*

Crane (1996)*Crane (2003)** ITU-R P.530-10 (2001)**

* Rain Zones

** Specific Locations

Crane is de facto standard in North AmericaITU-R is standard in Europe


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How Are Crane 2003 and ITU-R P.530 Different

Crane 2003 ITU-R P.530

Based upon 5 minute integration Based upon 1 minute integration

(commonly available) (less available)

Works for all probabilities Only works for 0.001% to 1%

(two 9s to five 9s,not possible to extend range)

Curves based upon actual rain data Rain curves are predetermined

(based upon 5 parameters derived (one for > 300 latitude,

from actual site data) one for < 300 latitude,

uses 0.01% unavail. value based

upon 3 interpolated parameters)

Point to Path conversion factors are quite different


7/39Copyright 2010 Alcatel-Lucent. All rights reserved.

Crane Model Based Upon Two Components

San Francisco Miami

Low Density Rain (debris ) Contribut ion = exponential distr ibution (two parameters)

Intense Rain Cell ( cell ) Contribution = lognormal distribution (three parameters)


8/39Copyright 2010 Alcatel-Lucent. All rights reserved.

ITU-R P.530 Based Upon Shapes and Offsets

Zone D3

Rain Distribution Shape 1 for latitude 300Rain Distribution Shape 2 for latitude < 300

Shape shifted up or down from 0.01% rain rate

Rain rate for 0.01% determined by

three geographically based parameters

Only applicable for probability between 0.001% and 1%

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Major Topics

MW Path Design





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Copyright 2010 Alcatel-Lucent. All rights reserved.10

M = R deff

M = path flat fade margin (dB)

R = single location (point) rain attenuation (dB/km)

deff= effective path length (km) = d Fpp

d = actual path distance

Fpp = point to path conversion factor



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R = point rain attenuation

= KR (db/km)

K and frequency dependant

R = site or zone rain rate (mm/hr)

for specific outage probability (e.g., 0.01%)



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Need for Current Point Rain Attenuation

More than 100 years of NOAA rain data


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Typical Rain City Data

typical measurement limit

(99.9999%) (99.99%)(99.999%)


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Why create curves for parameter model

(rather than actual measurements) ?

North American 11 GHz calculations for high availability require rainavailabilities as high as 99.99995% (0.00005% unavailability)

For 5 minute integrated data, that is one measurement in 20 years

Actual data does not have reliable values for high availabilities(those rain events are too rare)

Only the model can give reliable high availability estimates(it is based upon the underlying physical mechanisms)


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Rain City Data

Crane 2003 data has been augmented with Segal (CRC) and Kizer (NOAA) data

Data represents 282 cities in Canada and the United StatesCurves derived from curve fits of actual data to Crane 5 parameter rain model


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Why Migrate to Site Specific Rain Data?

Crane 1996

All zones are averages of a wide range of specific site data

Some zones misrepresent some locations


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Crane 1996 Rain Regions


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Zone C Zone F

Site Data Different than Zone Average


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Zone Average Misrepresents Site Rain Rates

Zone D2 Zone C


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Differences in Crane and ITU-R Site Data

Crane 2003 ITU-R P.530

Crane Zone B1

ITU rain curves are simpl ified to eliminate frequency dependency

This introduces about 10% error for frequencies between 11 and 23 GHz


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Differences in Crane and ITU-R Site Point Data

Crane 2003Crane Zone C

ITU-R P.530




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Crane 2003

Crane Zone D1

ITU-R P.530




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Crane 2003Crane Zone D2

ITU-R P.530




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Crane 2003

Crane Zone D3

ITU-R P.530




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Crane 2003

Crane Zone E

ITU-R P.530




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Crane 2003

Crane Zone F

ITU-R P.530




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Major Topics

MW Path Design





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M = R deff

M = path flat fade margin (dB)

R = single location (point) rain attenuation (dB/km)

deff= effective path length (km) = d Fpp

d = actual path distance

Fpp = point to path conversion factor



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Differences in Point to Path Factor


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Differences Due to Point to Path Factor

Crane Zone C Average Rain Rates

(low rain rate region)

ITU-R methods not valid for 99.9999% path availabil it ies


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Crane Zone D2 Average Rain Rates

(typical rain rate region)




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Crane Zone E Average Rain Rates

(high rain rate region)




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Major Topics

MW Path Design





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Philidelphia Example (2008-2009)


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Major Topics

MW Path Design





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Rain Fading - Kizer - Rev B

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