Path-Specific Propagation Models for Subgroup 3K-1 Propagation Models for Subgroup 3K-1 ... specific...

Path-Specific Propagation Models for Subgroup 3K-1

Paul McKenna, NTIA/ITS.E1

Alakananda Paul, NTIA/OSM2

National Telecommunications and Information Administration1Mr. McKenna is with the Institute for Telecommunication Sciences,

Boulder, CO2Dr. Alakananda Paul is with the Office of Spectrum Management,

Washington, D.C.

Introduction and Background

•

Six Path-Specific Models were proposed for study–

Each has a somewhat different rationale but a “common”

goal

–

Each is intended to optimize the radio propagation prediction on most paths

–

The optimal model will choose the “best”

parts of each model

Rec. ITU-R P.452

•

Clear Air Propagation Mechanisms– line-of-sight (including signal enhancements due to

multipath and focusing effects);– diffraction (embracing smooth-earth, irregular terrain

and sub-path cases);– tropospheric scatter;– anomalous propagation (ducting and layer

reflection/refraction);– height-gain variation in clutter (where relevant).

Rec. ITU-R P.452

Rec. ITU-R P.452•

Line-of-SightLb0

(p)

=

92.5

+

20 log(fd )+

Es (

p) + Ag dBwhere:Es (p)

: correction for multipath and focusing effects:Es (p) = 2.6 (1 –

e–

d / 10)log(p/50)

dBAg : total gaseous absorption (dB):

Ag

=[γo

+γw

(ρ)]dwhere:γo , γw (ρ)

: specific attenuation due to dry air and water vapor, respectively, and are found from the equations in Recommendation

ITU-R

P.676ρ

: water vapor density:ρ=7.5+2.5ω

g/m3

ω

:

fraction of the total path over

water.

Rec. ITU-R P.452

•

Diffraction

)50

log()1(6.2)(

)()()log(205.92)(100

100)(

%)]50()()[(%)50()(

10/)(

0

0

pepE

ApEpLdfpL

I

pIpF

LLpFLpL

lrlt ddsd

gsddbd

i

ddidd

+−−=

+++⋅+=

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛

=

−+=

β

β

Rec. ITU-R P.452•

Obstacle Height Above the Straight Line Between the Ends of the Path

Rec. ITU-R P.452•

Cascaded Knife Edge Diffraction (Deygout Construction)

( )

( )

( ) )78.0( 1.011.0log209.6)( where

04.010)()(1)(

,...,),max( and ,...,1),max(

find also then 78.0 if2

where2

path) los 0( ,...,1 ),max(

2

6)(

−>⎟⎠⎞⎜

⎝⎛ −++−+=

+++⋅⎟⎟⎠

⎞⎜⎜⎝

⎛−+=

====

−>

+−+==

⇒<==

−

νννν

ννν

νννν

νλ

ννν

ν

J

dJJeJL

npflpjpi

ddhdh

addhh

dddhv

npfln

rt

J

pd

jrit

p

ab

anbnba

e

nbann

nban

abn

pnp

p

Rec. ITU-R P.452

•

Tropospheric Scatter

rte

GGc

f

gcfbs

ad

eL

ffL

pALNdLpL

rt

θθθ

θ

++=

⋅=

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛−=

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛−++−+++=

+

3

)(055.0

2

7.0

0

10051.0

2log5.2log25

50log1.1015.0573.0log20190)(

Rec. ITU-R P.452

•

Anomalous Propagation (Ducting & Layer Reflection/Refraction)

),)(log()correction roughnessterrain ()correctiongeometry path (

)(12)log()107.32.1(12)(

)1.0,min()1.0,min(10

)(105)(

))(log(2045.102

)()(

0

3

3

3/15

d

ppdpA

dda

d

pAfapA

AAAAddfA

ApAApL

lrrltte

ed

crctsrstlrltf

gdfba

βββ

ββ

θθθ

θ

Γ=Γ⋅⋅=

+⋅++−=

++=′

+′⋅=

++++++=

++=

Γ−

−

Rec. ITU-R P.452

•

Anomalous Propagation (Ducting & Layer Reflection/Refraction)

[ ]

scorrection ducting surface sea-over are 0

01.0

264.0361.01log20

,

,

,,'',

31

'',,

'',,

crct

srst

lrltrtrt

rtlrltrtsrst

AAotherwise

dif

fdfA

=

>−=

+⋅+=

θθ

θθ

Rec. ITU-R P.452•

Height Gain Variation in Clutter

dk : distance (km) from nominal clutter point to the antenna h :

antenna height (m) above local ground levelha : nominal clutter height (m) above local ground level.

33.0625.06tanh125.10 −⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛⎥⎦

⎤⎢⎣

⎡−−= −

a

dh h

heA k

Rec. ITU-R P.452TABLE 6

Nominal clutter heights and distances

Clutter (ground-cover) category Nominal height, ha (m)

Nominal distance, dk(km)

High crop fields Park land Irregularly spaced sparse trees Orchard (regularly spaced) Sparse houses

4

0.1

Village centre 5 0.07 Deciduous trees (irregularly spaced) Deciduous trees (regularly spaced) Mixed tree forest

15

0.05

Coniferous trees (irregularly spaced) Coniferous trees (regularly spaced)

20 0.05

Tropical rain forest 20 0.03

Suburban 9 0.025

Dense suburban 12 0.02

Urban 20 0.02

Dense urban 25 0.02

Industrial zone 20 0.05

Rec. ITU-R P.452-12

•

The Overall Prediction–

Line-of-Sight

–

Line-of-Sight with sub- path diffraction

hrhtbb AApLpL ++= )()( 0

hrhtdsbb AApLpLpL +++= )()()( 0

Rec. ITU-R P.452-12

•

The Overall Prediction–

Trans-horizon

( )

( ) ( )

( )[ ]

( ) hrhtpLpLpL

b

jibibd

jkbdk

pLpL

bam

jk

AApL

FpFLpFL

FdFpLdFeepL

FddF

bdbambs

bba

++++⋅−=

⋅⋅+−⋅+

−⋅⎥⎥⎦

⎤

⎢⎢⎣

⎡⋅+−⋅⎟⎟

⎠

⎞⎜⎜⎝

⎛+=

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛ −

+⋅−=⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛ −

+⋅−=

−−− )(2.0)(2.0)(2.0

00

5.2)(

5.2)(

101010log0.5)(

)()()()(1%)50(

)(1)()()(1ln5.2)(

3.0)3.0(4.2tanh15.01)(,

20205.1tanh15.01)(

0

θβ

θ

θθ

CHINESE METHOD(1)•

Median field strength based on ITU-R Recs. P.452, 526 and time/location variability based on ITU-R Rec. P.1546

•

Median basic transmission loss is sum of free-space basic transmission loss and median attenuation relative to free space

•

Three path types: LOS with first Fresnel zone clearance, LOS with sub-path diffraction, transhorizon path (diffraction and troposcatter)

•

Clutter loss includes those for transmitting and receiving stations

CHINESE METHOD(2)

Field strength for

T% time

and

L% locationE(T,L) = E(50,50) + ΔEt (T) + ΔEl (L)

ΔEt (T), ΔEl (L): variations for time, location

Median field strength E(50,50)E(50,50) = ERP - Lb (50,50) + 20 log

f +109.4Lb (50,50): median basic transmission loss

ERP: effective radiated power (dBW)f: frequency (MHz)

Median basic transmission loss

Lb (50,50) Lb (50,50) = Lbf + A(50,50)

A(50,50): median attenuation (dB) relative to free spaceLbf; : free space basic transmission loss (dB)

CHINESE METHOD(3)LOS path with first Fresnel zone clearance

Lb (50,50) = Lbf + Acldt + Acldr

Acldt , Acldr : additional clutter losses due to diffraction

LOS path with sub-path diffractionLb (50,50) = Lbf + Acldt + Acldr + Ad (50,50)

Ad (50,50): median sub-path diffraction loss (P.526)

Trans-horizon pathLb (50,50) = -10 log {10-0.1L

bd(50,50)

+ 10-0.1Lbs

(50,50)}Lbd : median basic transmission loss due to trans-horizon diffraction

Lbs : median basic transmission loss due to troposcatter

CHINESE METHOD(4)Median basic transmission loss due to trans-horizon diffraction

Lbd (50,50) = Lbf + Acldt + Acldr + Adt (50,50)Adt for spherical earth, 3.1.1.2 in ITU-R P.526-8

for irregular earth, 4.4.2 in ITU-R P.526-8

Median basic transmission loss due to troposcatterLbs (50,50) = Lbso (50,50) + Acls

Lbso (50,50): median basic transmission loss due to troposcatter without clutter based from Eq.15 in ITU-R P.452-12

Acls : clutter loss due to scatter

CHINESE METHOD(5)Location Variability

ΔEl (L) = Qi (L/100) σL (f)Qi (x): the inverse complementary cumulative normal distribution

σL : the standard deviation

Time variabilityΔEt (T) = E(T)

– E(50)E(T): field strength for T% time

Based on ITU-R P.1546 tabulated field strengths and relevant ITU-R P.453 climatic data files

Corrections for receiving antenna heights and clearance angle not done

PSPROGCN-1•

FUNCTION E50 (F,ERP,NPL,HTG,HRG,N,HI,DI,NGC,HGC,ALON1,ALAT1, ALON2,ALAT2) for calculation of the median field strength

•

FUNCTION DETT (F,T,HTG,N,HI,DI,GNC,ALON1,ALAT1,ALON2,ALAT2)for calculation of the variation with time

•

FUNCTION ETQ (F,ERP,NPL,HTG,HRG,N,HI,DI,NGC,HGC,ALON1,ALAT1, ALON2,ALAT2,T,Q)for calculating of field strength for any time and location percentages

PSPROGCN-1

•

FILES DNZ.TXT,NO.TXT,IDN.TXT AND FST.TXT filesfor basic climatic and field strength data

•

MAIN PROGRAMfor opening the basic climatic and field strength data files and the measurement data files, reading and processing the data, calculating field strength and comparing it with measured field strength, and putting the results into the output data file

PSPROGCN-1Input Parameters•

frequency

•

effective radiated power•

polarization

•

antenna heights above ground level•

distance from transmitting/base station, terrain height amsl, ground cover type and its height at the ith

terrain point on the

path profile•

latitude and longitude of transmitting/base station

•

latitude and longitude of receiving/mobile station•

percentage of time

EBU METHOD(1) Propagation Mechanisms

•

Free space•

Diffraction loss (irregular terrain and sub-path

•

Tropospheric scatter•

Anomalous propagation (ducting)

•

Height variation in ground cover•

Building penetration

EBU METHOD(2) Basic Input Data

Parameter Description

f Frequency (MHz)

p Required time percentage(s) for which the basic transmission loss is not exceeded

φt

φr Latitude of transmitter and receiver (degrees)

ψt

ψr Longitude of transmitter and receiver (degrees)

htg

hrg Transmitter and receiver antenna center height above ground level (m)

hts

hrs Transmitter and receiver antenna center height above mean sea level (m)

Gt

Gr Transmitter and receiver antenna gain in the direction of horizon along great circle path

EBU METHOD(3) Radiometeorological data

•

ΔN (N-units/km), average radio-refractive index lapse rate through the lowest 1 km of the atmosphere (world map of average annual ΔN in Rec. p.452)

•

β0

(%),time percentage for which refractive index lapse-rates exceeding 100 N-units/km expected in the first 100 m

•

N0

(N-units), the sea-level surface refractivity (world map of annual N0 in Rec. p.452)

EBU METHOD(4) Parameters derived from path profile analysis

Path type Parameter Description

Transhorizon d Great-circle path distance in km

Transhorizon dlt

dlr Distance from transmit and receive antennas to their respective horizons in km

Transhorizon θt

θr Transmit and receive horizon elevation angles

Transhorizon θ Path angular distance

All hts

hrs Antenna center height above mean sea level

EBU METHOD(5) Path classifications and propagation models

LOS with first Fresnel zone clearance•

Free space basic transmission loss

•

Relative ground cover and receiving antenna height loss

•

Building penetration loss (where appropriate)


LOS with sub-path diffraction•


•

Diffraction•


•



Trans-horizon•


•

Diffraction•

Troposcatter

•

Ducting•


•


EBU METHOD(7.1)

Electric field strength for 1 kW e.r.p Eb = 139

– Lb + 20 log

f dBμV/m

Lb is basic transmission loss in dBFree space basic transmission lossLbf = 32.4 +20 log f + 20 log d dB

Diffraction lossBased on ITU-R P.452 and P.526

Assumes a horizontal exclusion zone of the principal obstacle to avoid over-estimating loss

EBU METHOD (8)

Line-of-sightField Strength Eb

= 106.9 -20 log d –

(Ahr

+ Abl

) dB Ahr : additional ground cover and receiving antenna

height lossAbl : additional losses due to building penetrationLine-of-sight with sub-path diffractionField Strength Eb

= 106.9 –

20 log d -

(Ld

+ Ahr

+ Abl

) dB

Ld : sub-path diffraction loss for p% of time

L

EBU METHOD (9)

Trans-horizonEb

= 10 log(10Ed/10

+10Es/10

+ 10Ea/10) –

(Ahr

+ Abl

) Ed

= 106.9 –

20 log d –

LdLd

: diffraction loss for p% of timeEs

= 106.9 –

20 log d –

LsLs : troposcatter loss for p% of timeEa

: field strength resulting from ducting

SWISS STUDY•

Comparison of predicted results with measured data in Alpine region

•

Three diffraction modeling techniques: Bullington, Epstein-Peterson and Deygout methods and Longley-

Rice model used•

Terrain profile from DBSG5 and Shuttle Radar Topography Mission (SRTM) data

•

Bullington method gives consistently optimistic results with relatively small errors, other methods overestimate path loss with larger errors

Irregular Terrain Model (ITM)

•

Computed Reference Attenuation (Attenuation Relative to Free Space)

xlsref

xses

xlsded

lsls

kkelref

dddAdddmA

ddddmA

ddddadaaA

,at continuous is for for

for )ln,0max( 21

=>+=

≤<+=

≤⎟⎟⎠

⎞⎜⎜⎝

⎛++=

Irregular Terrain Model (ITM)•

Time, Location and Situation Variabilities; Attenuation not exceeded for pT (percentage Time), pL

(percentage Locations) and pS

(percentage Situations), A(pT

,pL

,pS

):

( ) ( )

( ) ( )

( ) ( )

( )

0 if 1029

29

0 if ,,

deviation standard theis andmean theis where usingthen 21 and )( where

100,

100,

100)(),(),(,,

''

''

''

'00

1 2

<⋅−

−=

≥=

−−−−=

⋅+=

===

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛=≡

∫∞

−−

AA

AA

AAzzzA

YYYVAA

XqzXqX

dtezQqqQqz

pzpzpzAqzqzqzAzzzA

SLT

SLTmedref

z

t

SLTSLTSLT

σσπ


•

Coefficients for the Diffraction Range

( )

3334

34

44

33

34

3

31

31

2

,

)(

)(7574.2

3787.1,max2

2

dmAAddAAm

dAA

dAAXdd

Xdddda

aa

X

dedd

diff

diff

ae

aelrltls

ee

eae

−=−−

=

=

=+=

++=

⎟⎟⎠

⎞⎜⎜⎝

⎛=⎟⎟

⎠

⎞⎜⎜⎝

⎛=

−

πλ

λπ


•

The function Adiff

(s)

( )forkdiff

lshgrgtfo

sh

e

lrltrte

s

eelrlt

grgt

eret

AAwAwsA

dhkhAeshsm

addhesh

sadd

hhhhshQ

Qw

+⋅+⋅−=

+=⋅Δ⋅=×=

⎟⎟⎠

⎞⎜⎜⎝

⎛ +−+=Δ⋅⎟

⎟⎠

⎞⎜⎜⎝

⎛−=Δ

⋅+++⎟

⎟⎠

⎞⎜⎜⎝

⎛

++

⋅⎟⎠⎞

⎜⎝⎛ Δ=

+=

⎟⎠⎞

⎜⎝⎛ Δ−

−−

×−

)1()(

))(1log(5,15min)(78.0)( ,1077.4

,max ,8.01)(

101010,)(min

1.011factor weighting

41

4

16)(

24

105

21

3

σασα

θθθ

θλ


•

The function Adiff

(s), continued

( )( )

( ) ( )

( ) ( )( ) ( ) ( ) ( )010

000,,,,,

,,0,,0

31

2,,0

,,02,

,,0

2

21

,

,,

,,03.151 ,03.151

1 , ,2

,

21log20)( where,

22

, ,

2

KCKxFKxFxGAxxKBxdKBx

ZiKk

dh

ds

duei

FnFnFnA

ddsdsd

dddas

rrttr

rtlrltrtrtrtrt

grtrt

rtrt

lrlt

eretrt

l

ui

rtk

lrltl

llrltrtlrltl

ee

−−−=

++⋅=⋅=

=⎟⎟⎠

⎞⎜⎜⎝

⎛==

−=

=+=

⎟⎟⎠

⎞⎜⎜⎝

⎛

+−−⋅

⋅=+=+=

∫∞

θαγα

αγαγθγ

ννν

λθνθθ

ν

π


•

Coefficients for the Line-of-Sight Range, Ael

, ak1

, ak2

:

( ) ( ) ( ) ( )

( ) ( )

( )

( )

elseamaelse

aaaaif

dd

AAa

elseaaaaaif

ddddaAA

a

dddd

dddd

AAddAAdda

dAAdAAdddhkhdd

thenAifdmAAdd

kdk

kkkk

k

kkkkk

k

k

k

loslosl

eretl

ed

dedls

0 , ,00

ln

,0

ln

lnln,0max

)( ),(,4

3 ,908.1,2

min

)0( ,

21

"221

"2

0

2

02"2

'22

'11

'1

02

0

2'202

'1

0

201

0

102

02010102'2

11000

10

222

====≥

⎟⎟⎠

⎞⎜⎜⎝

⎛−

=

==≥

−

⎟⎟⎠

⎞⎜⎜⎝

⎛−−

=

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛

⎟⎟⎠

⎞⎜⎜⎝

⎛⋅−−⎟⎟

⎠

⎞⎜⎜⎝

⎛⋅−

−⋅−−−⋅−=

==+

=⎟⎠⎞

⎜⎝⎛=

≥+==


•

Coefficients of the Line-of-Sight Range, continued:

212

21

2"11

12

12"111

'201

'1

'2

'2110010

10

0 ,

0 , , ),()0 (

above described as proceed and )0(

),( ),() (

4,max ,908.1

daAAendif

endifamaelse

aaaddAAadAAaorddelseif

aevaluateaif

aevaluatedAAdAAddif

dmAdhkhd

kel

kdk

kkkklosk

kk

kloslos

l

d

ederet

−=

==

==−−

===<

>

==<

⎟⎟⎠

⎞⎜⎜⎝

⎛ −==


•

The function Alos

(s)

( )

δietdedd

tdlos

ls

eRAsmAA

wAAwAd

hkw

+−=+=

+−=

Δ×+

=

1log20 ,

)1(,10max

1077.41

1factor weighting

4

1


•

The function Alos

(s), continued

( )

( )( )

'

2''

'

'

'''

0'

'

'

g

'

22

sin)('e

4 ,

2

2

sin ,sin,5.0max

onpolarizati alfor vertic 1

Z

onpolarizati horizontalfor 1

sin ,sinsin

R

δππδδδπδ

δ

ψψ

σεε

εε

ε

ψψψ ψσ

−==⎟⎠⎞

⎜⎝⎛ ≤

=

⋅==≥

+=

−=

−=

++

+=⋅

+−

= −

elseif

shkh

RRRelseRRRif

kZi

Z

hhs

hheZZ

eret

e

eeeee

rr

r

r

rg

eret

eretsk

g

g h


•

Coefficients of the (Tropo)Scatter Range

( )

( ) ⎟⎟⎠

⎞⎜⎜⎝

⎛−−−

×⋅+=

−+=×−

=

==×+=×+=

sd

sedaellsx

xsdedes

s

scatscat

l

mmdmAAkXddd

dmmAA

AAm

dAAdAAdddd

551

556

6655

556

55

,1077.4log,max

where,102

)( ),(102 ,102


•

The function Ascat

(s)

( ) ( )

9.2)Section V1,-(TN101Function Gain Frequency theis 9.1)Section V1,-(TN101Function n Attenuatio the torelated is ),(

where,1077.4log10)()2.0&(

2 , ,

0

041

,'

,'

HNsF

HNsFksArrif

hkras

as

s

sscatrt

eretrte

rte

e

θ

θθ

θθθθθθ

++×=≥

=++=+=


•

The Attenuation Function, F(θs, Ns

)

( )

( )

)ln(171.21057.18.71)301,()107(

)ln(086.11012.26.104)301,()10710(

ln343.41032.34.133)301,()10(

3011.0)301,(),(

4

4

4

44

4

4

104 4

sssFsif

sssFsif

sssFsif

eNsFNsFs

ss

θθθ

θ

θθθ

θ

θθθ

θ

θθθ

+×+=

<×

−×+=

×≤<

−×+=

≤

⋅−⋅−=

−

−

−

×−


•

The Frequency Gain Function, Ho

:

( )( ) ( )

( )( ) ( )( )

( )

( ) ( ) ( )( ) ( ) ( ) ( )

( ) ( )

9.2)Section V1,-TN101 (see nsrestrictio some subject to loglog)log6.0(6 where

2

11or 5for 0 , ,51 ,intlet and 5,...,1for 1log10

108 and 10756.1 with 1067.51032.2101.31

41 ,

2

2 ,

0

000

0

,1,0,,0,0

4,

2,,,0

31

30

6232

0

0

'

2

'

0

6

1

0

⎟⎟⎠

⎞⎜⎜⎝

⎛−=Δ

Δ++

=

⋅+⋅−=

<>≡−=≤≤==⋅+⋅+=

×=×=⎥⎥

⎦

⎤

⎢⎢

⎣

⎡×+×−×+=

−+−−=

+=

−−−+

=+

+=−−=

+

−−

⎟⎟⎠

⎞⎜⎜⎝

⎛−

−−−

ts

rss

rt

rtirtirt

ssssrtirtirti

Zz

sss

lrltlrlt

s

s

lrlt

lrlt

slr

slt

slrlts

rSrSH

HrHrHH

rHQrHQrHQiQiiirArBrH

ZZeNNZz

sddsdds

SsSz

ddsdds

dd

ddSddsd

η

ηηηη

η

θθ

ηη

ηηη


Time, Location and Situation Variabilities; Attenuation not exceeded for pT (percentage Time), pL

(percentage Locations) and pS

(percentage Situations), A(pT

,pL

,pS

):

( ) ( )

( ) ( )

( ) ( )

( )

0 if 1029

29

0 if ,,

deviation standard theis andmean theis where usingthen 21 and )( where

100,

100,

100)(),(),(,,

''

''

''

'00

1 2

<⋅−

−=

≥=

−−−−=

⋅+=

===

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛

⎟⎠⎞

⎜⎝⎛=≡

∫∞

−−

AA

AA

AAzzzA

YYYVAA

XqzXqX

dtezQqqQqz

pzpzpzAqzqzqzAzzzA

SLT

SLTmedref

z

t

SLTSLTSLT

σσπ


•

The Effective Distance for Variabilities, de

:

( )

exex

exex

e

eretex

dddd

ddddd

DakDahahad

>−+×=

≤×=

×=×=⋅++= −

for 103.1

for 103.1

10266.1 ,109 ,22

5

5

61

613

1

1111


•

Time Variability, Vmed

(de

,clim):


•

Time Variability, the deviation YT

:

( )( ) ( ) ( )

+±±

+

+

−

===

≤−+=

≤≤=

≤=

TDDDeTT

TDTDDTTD

DTTT

TTTT

Czzd

zzzzz

zzz

zzY

σσσσ

σσ

σ

σ

clim ,clim ,clim,

for

0for

0for

TD


Location and Situation Variability, the deviations YL and YS

:

51021

2

2

2

22

L

35 ,248.7

13)()(10 ,

ed

SS

L

S

TSSS

LLL

ez

Yz

YzY

dhkdhkzY

−+=⎟⎟

⎠

⎞⎜⎜⎝

⎛+

++

+=

+ΔΔ

==

σσ

σσ

SSMD or the NTIA Model•

SSMD (or the NTIA Model) is a Hybrid Combination of Site-Specific and Site-General Approaches with “Similarities”

to the ITM Approach

–

Sea Curves of Rec. ITU-R P.1546 (50% Time) for Propagation over a Smooth Spherical Earth

–

Irregular Terrain Diffraction Using the Deygout Three- Edge Construction of Rec. ITU-R P.526 (Minus the

Smooth Sphere Contribution): re @ 50% Time•

Combine These Using ITM’s “Diffraction Range”-like Weights–

Troposcatter Using Rec. ITU-R P.452 When This Yields Less Attenuation Than the Above

–

Use the Rec. ITU-R P.1546 Land Curve Differences to obtain Time Percentages between 50% and 1%

SSMD or the NTIA Model

•

Sea Curves from Rec. ITU-R P.1546–

Interpolate for Required Value of Distance, then Interpolate/Extrapolate for Required Values of h1 and f

–

h1 Computed Using Terrain Heights from 2 –

15 km Distances from This Designated Terminal (but Always Greater Than or Equal to 1 m), however use the UK’s method of extrapolation for 0 ≤

h1 ≤

10 m.

–

Include the h2 Correction When This Terminal’s Height Above Ground Is Not Equal to 10 m

SSMD or the NTIA Model/Sea Curves

Rec. ITU-R P.1546-2 100 MHz Sea Curves (50% Time)

-80-60-40-20

020406080

100120

1 10 100 1000

Distance (km)

Fiel

d St

reng

th R

elat

ive

to 1

kW

ERP

(dB

mic

rovo

lt/m

) 102037.5751503006001200fs



-80-60-40-20

020406080

100120

1 10 100 1000

Distance (km)

Fiel

d St

reng

th R

elat

ive

to 1

kWER

P (d

B m

icro

volt/

m) 10

2037.5751503006001200fs



-80-60-40-20

020406080

100120

1 10 100 1000

Distance (km)

Fiel

d St

reng

th R

elat

ive

to 1

kW

ERP

(dB

mic

rovo

lt/m

) 102037.5751503006001200fs


The Smooth Sphere Contribution, Ar

’–

Under line-of-sight conditions this should yield a direct ray-reflected ray model for a “smooth”

earth–

Under line-of-sight without first Fresnel zone clearance this should yield sub-

path diffraction

–

This latter method should blend smoothly into smooth sphere diffraction

( ) ( ))log(209.106)(

%50,,, 1,1546.'

ddE

fhdEdEA

fs

sPfsr

−=

−=

SSMD or the NTIA Model/Diffraction

Geometry for Deygout Construction

SSMD or the NTIA Model/Diffraction

•

Cascaded Knife Edge Diffraction (Deygout Construction)

( )

( )

( )

0

0

'

2

6)(

return

result to set the and ,...,1 ,0 with procedure srepeat thi

)78.0( 1.011.0log209.6)( where

04.010)()(1)(

,...,),max( and ,...,1),max(

find also then 78.0 if2

where2

path) los 0( ,...,1 ),max(

ddk

dn

rt

J

pd

jrit

p

ab

anbnba

e

nbann

nban

abn

pnp

LLA

Lnpflnh

J

dJJeJL

npflpjpi

ddhdh

addhh

dddhv

npfln

p

−=

==

−>⎟⎠⎞⎜

⎝⎛ −++−+=

+++⋅⎟⎟⎠

⎞⎜⎜⎝

⎛−+=

====

−>

+−+==

⇒<==

−

νννν

ννν

νννν

νλ

ννν

ν


The Weighted Combination of Smooth Sphere and Cascaded Knife Edge Diffraction, Comparison to Troposcatter and the Final Prediction

( ) ( ) ( )( )( ) ( )( )%50,,,,,,

,min

)2()(

,max ,8.01)(

101010,)(min

039.011factor weighting

1,1546.1,1546.50

50,'

50

'''

50

21

3

fhdEpfhdEAA

dEdEdAA

AwAwdA

addhedh

dadd

hhhhdhQ

Qw

lPlPp

tropofsdiff

rkdiff

e

lrltrte

d

eelrlt

grgt

eret

−+=

−=

⋅+⋅−=

⎟⎟⎠

⎞⎜⎜⎝

⎛ +−+=Δ⋅⎟⎟

⎠

⎞⎜⎜⎝

⎛−=Δ

⋅+++⎟

⎟⎠

⎞⎜⎜⎝

⎛

++

⋅⎟⎠⎞

⎜⎝⎛ Δ=

+=

−θθθ

θλ

Comparisons of the Path-Specific Models’

Features

•

Terrain (possibly Irregular Terrain) Diffraction Mechanisms

•

Line-of-Sight Mechanisms•

Troposcatter Mechanisms

•

Anomalous Propagation Mechanisms•

Land Use–Land Clutter/Site-Shielding Mechanisms

•

Building Entry Loss Mechanisms•

Radiometeorological Parameters and Time, Location (and Situation) Variabilities

•

Blending the Mechanisms (i.e., predicting enhancements at low time percentages)

Comparison of the Models’

Features•

Terrain Diffraction Mechanisms–

the Rec. ITU-R P.452, the Chinese and EBU Models each use the Deygout 3 knife-edge construction as found in Rec. ITU-R P.526

•

the EBU Model restricts the location of the subsidiary edges•

the Chinese Model uses smooth sphere diffraction for “flat”

paths•

Some differences in how the time variability is treated, Chinese

Model uses P.1546, while the others blend to reach the desired time percentage

–

the SSMD/NTIA Model uses the Deygout 3 knife-edge construction with the “smooth earth”

contribution removed plus smooth sphere diffraction from the P.1546 Sea Curves

•

median only until the Rec. ITU-R P.1546 land curves are factored in–

the Swiss Model advocates the Bullington Method•

median only–

the ITS’

ITM uses “double knife-edge”

plus smooth sphere diffraction attenuation plus an additional clutter correction, Afo , to account for obstructions between the radio horizons

•

median only, until the time, location and situation variabilities are factored in


Features (cont’d)

•

Line-of-Sight Mechanisms–

the ranges at which these mechanisms take place differ between the models

•

ITM appears to be much different from the Rec. ITU-R P.452 based models in this regard

–

All models use free space loss as the “dominant” mechanism with first Fresnel zone clearance

•

Rec. ITU-R P.452 includes multipath enhancements for time percentages less than 50%

–

Most models account for loss of first Fresnel zone clearance via sub-path diffraction

–

ITM includes the ground reflection contribution•

the other models do not explicitly do so, other than a nominal contribution in SSMD/NTIA


Features (cont’d)

•

Troposcatter Mechanisms–

These give rise to signal enhancements at (generally) small time percentages

–

The ITU-R P.452/Chinese/EBU Model is designed to blend smoothly with the other signal enhancement mechanisms

–

The ITM mechanism is designed to match with empirical and physical models of the expected phenomena.

–

The SSMD/NTIA uses the absolute prediction of the ITU- R P.452 Model to predict troposcatter losses


Features (cont’d)

•

Anomalous Propagation Mechanisms–

Explicitly treated through Rec. ITU-R P.452 (not including the Chinese Model) based models

–

Treated through the variabilities in ITM and P.1546 variability based models

•

Land-Use/Land-Clutter/Site-Shielding Losses–

each model’s formulation is different

–

Chinese and EBU’s Models for LU-LC losses have frequency dependence

•

Building Entry Loss–

A feature of the EBU Model only, but this could be adopted by the other models


Features (cont’d)

•

Radiometeorological Parameters and Time, Location and Situation Variabilities–

P.452, the Chinese and EBU models take global maps of radiometeorological parameters into account to assess effects of

time variability into account

–

ITM uses the radio climate to assess time variability, but requires user specification of the radio climate

–

all of the models take time variability into account•

each assumes that the time variability is normally distributed–

some models (P.452, Chinese and EBU) take the time percentage, p%, explicitly into account in the computation of all propagation mechanisms while others combine the variabilities after computation of an overall mean/median

•

Location and Situation Variabilities are an open question: only ITM considers situation variability


Features (cont’d)

•

Blending the Different Mechanisms–

ITM method: forces continuity at the “break points”, requires a continuously increasing attenuation with path distance

–

Rec. ITU-R P.452 method:•

blend via antilog-log combining process plus other mechanisms

( )⎟⎠⎞

⎜⎝⎛ ++

⋅= bA

bA naa

abA)(ln...ln 1

i.e.,

Path-Specific Propagation Models for Subgroup 3K-1 Propagation Models for Subgroup 3K-1 ... specific...

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