CSNDSP 2006 Iran Telecommunication Research Center 1

Flat Fading Modeling in Fixed MicrowaveRadio Links Based on ITU-R P.530-11

Iran Telecommunication Research Center (ITRC)

Mehrbod Mohajer, Ramin Khosravi, Mehrnoosh Khabiri

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Outlines

Introduction Outage Calculation Fading Prediction in ITU-R P.530-11 Simulations Conclusion

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Propagation Scenarios in LOS Point-to-Point Links

0452-01

Tropospheric scatter

Diffraction

Line-of-sight

0452-02

Hydrometeor scatter

Elevated layer reflection/refraction

Ducting

Line-of-sight with multipath enhancements

Link Design

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What is the Problem? In multi path situation,

several rays with different delays and amplitudes are constructively or destructively added to the ray of direct or line-of-sight (LOS) path which introduce signal fluctuations.

If the signal falls below a certain point the link can be considered to be non functioning.

Outage

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What can we do about it? We cannot possibly know all the details of the environment

through which the signal propagates.

We need to take a statistical view of the behaviour of the received field strength.

It is necessary to model the fading effects in such a way that a reasonable fade margin is obtained to achieve acceptable outage time.

Regarding to PTP links are used ashigh-availability links in the backboneof networks, the model should have thedetailed shape of low probability section of distribution.

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Which Model? Traditionally, the well-known lognormal

distribution is widely used in the fixed wireless system design procedure.

In order to evaluate the performance of high-availability links, a distribution fading model is required which can precisely present the deep fade depths probability distribution.

Conventional distributions can not provide the detailed shape of deep fade depths probability.

The ITU-R P.530-11 model derived from empirical measurements can perform this task excellently.

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All Important Propagation Standards

ITU-R P.530-11 (2005)

TIA-845: Radiowave

Propagation

ETSI: BRAN HIPERACCESS

IEEE 211-1997

IEC 60050-705

Why ITU-R P.530-11?

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Propagation Effects in ITU-R P.530

Fading

Multi-Hop Links

Rain Attenuation

XPD

Diffraction

Distortion

Variation in Angle of

Arrival/Launch

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Outlines

Introduction Outage Calculation Fading Prediction in ITU-R P.530-11 Simulations Conclusion

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Fade Margin Concept

Transmitter 1

Receiver 1

Splitter Splitter

Transmitter 2

Receiver 2

OutputPower (Tx)

Branching Losses

waveguide

Pro

paga

tion

Los

ses

Ant

enna

G

ain

Ant

enna

G

ain

Branching Losses

Receiver threshold Value

Fade Margin

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Outage Time

t

RSL

Noise power threshold

Fade Margin

The real RSL value which

varies in time due to fading

processes.

The RSL value for a path subject

to Free-space and atmospheric

attenuation only.

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Improving Outage Time

t

RSL

Free-space and atmospheric

losses.

Noise power threshold

Fade Margin

By increasing the fade margin, we can improve the outage time.

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Outlines

Introduction Outage Calculation Fading Prediction in ITU-R P.530-11 Simulations Conclusion

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Fading Prediction in ITU-R P.530-11

Flat Fading Prediction For Small Percentage of Time

(Deep Fade Depths) For All Percentage of Time

(Shallow and Deep Fade Depths)

Selective Frequency Fading Prediction

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Flat Fading (Deep Fade Depth)

kmdkm 1855.7 GHzfMHz 37450 mradp 37

%101 1000085.0032.097.02.3

Ahf

pwL

Kdp

42.0003.09.3 110 adN sK

%101 10001.0033.02.10.3

Ahf

pwL

Kdp

10029.02.410 dNK dhh erp

mhm L 230017 kmNunitdNKmNunit /150/860 1 8506 as

Detailed Link Design Applications Quick Planning Applications

These relations were derived from multiple regressions on fading data for 251 links in various geo-climatic regions of the world with

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Flat Fading (Shallow and Deep Fade Depths)

%10

1)0(

00085.0032.0

97.02.30

Lhf

pw KdApp

%10

1)0(

001.0033.0

2.10.30

Lhf

pw KdApp

dBpAt 0log2.125

%10 10/0

Aw pp %10 10/

0tA

t pp

%10exp1100 20/Aqw

ap

Detailed Link Design Applications Quick Planning Applications

)),,(),,(( AAqqApqfq tatttaa

AAt AAt Deep Fade Depths Shallow Fade Depths

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Outlines

Introduction Outage Calculation Fading Prediction in ITU-R P.530-11 Simulations Conclusion

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Simulations

Fade probability for ITU-R P.530-11

and Lognormal models

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PDF of the ITU-R P.530-11 model

Deep fade depths probability Shallow fade depths probability

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Simulations

BER of QPSK modulation with various channel

models

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Conclusion The outage calculation and fade margin concept are

reviewed. The prediction methods of multi-path fading are

introduced based on ITU-R P.530-11 standard. The ITU-R P.530-11 model is more accurate in

comparison to the conventional models like Lognormal model.

It is shown that using the theoretical lognormal model instead of empirical ITU-R model will cause to overestimation or underestimation in link design calculations.Therefore, p

lease use ITU-R

P.530

model in your li

nk design

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Any Question?

Thanks For Being Such a Good Audience