Propagation model tools using Rec. ITU-R P.1812 and P
Transcript of Propagation model tools using Rec. ITU-R P.1812 and P
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Propagation model tools using Rec. ITU-R P.1812 and P.1546
By Andrea ManaraBroadcasting Service Division
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➢Short presentation➢ Rec. ITU-R P.1812 and P.1546 propagation
models➢ eTools calculations (new P.1812 fs contours!)➢Use cases
➢Demonstration of propagation calculations in eTools
Agenda
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Comparison Rec. ITU-R P.1812 vs P.1546
Deterministic modelmodel all the physical phenomena which plays a role in VHF-UHF band
Path specificUses terrain profile (elevation above mean sea level).
➢ 30 MHz - 3 GHz➢ 0.25 km - 3000 km➢ 1% < time < 50%➢ 1% < locations < 99%➢ Rx and Tx hgt agl <= 3km
Empirical model based on extensive field measurements and statistical analysisPath generalThe effect of terrain only via:• Effective antenna height• Clearance Angle correction• Tropospheric scattering correction
➢ 30 MHz - 4 GHz➢ 1 km - 1000 km➢ 1% < time < 50%➢ 1% < locations < 99%➢ Rx and Tx hgt agl <= 3km
Interference/coverage analyses!
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Field-strength curves as functions of distance, antenna height, frequency and percentage time
• Land, warm sea, cold sea• 100, 600, 2000 MHz• time percentage: 1,10,50
Method • interpolation/extrapolation• mixed-path
Rec. ITU-R P. 1546
Important correction for refractivity index!!
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Rec. ITU-R P. 1812
Refraction
Adapted from LS Telecom Propagation training material
Propagation mechanisms in the VHF/UHF band
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eTools: Input parameters
Point to Point
Point to Area
ITU-R P.1812
Point to AreaITU-R P.1546
Environment Type
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ATSC
50% locations
90% time
Coverage Analyses (wanted signal) (Report BT.2383-1)
DVB-T , DVB-T2, DTMB
95% locations
50% time
ISDB-T
95% locations
90% time
Analogue TV
50% locations
50% time
Rec. SM-851-1
Interference Analyses (un wanted signal)
50% locations
1% time
Report ITU-R BT.2383-1 (Note 19 on page 26)
Provides formula for applicability of Rec.
P.1546 for 90% of time.
WP 3K Liaison Statement to the Director BR (March
2017). The 90% formula is not generally applicable.
It errs on the conservative/safe side for the desired
signal in interference/compatibility analyses which
compare desired-to-undesired signal ratios
eTools: Input parameters
Percentage of time and location
FM
50% locations
50% time
GE84 Agreement
Clutter Type Reception Type Polarization
ITU-R P.1812
FM (tropo)
50% location
1% time
FM (steady)
50% location.
50% time
Accord GE84
N.B. If clutter heights are not given, the software uses the representative heights from Table 2
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1 degree resolution 10 degree resolution
eTools: rec. ITU-R P.1812 calculations
Point to AreaBeta Release! coverage analyses
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Point to Point
eTools: rec. ITU-R P.1812 calculations
Study FS variation on the path from TX to a RX point in the contours farthest from the TX in the P2A coverage analyses
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GIS Analysesfield strength contours
Beta Release!
1) P.1812 vector data (location and fs)
2) Convert to raster 3) Interpolate to fill voids
4) Extract fs_wanted contour5) Simplify geometry
dB(μV/m)
OSGeo: GDAL/OGR open source libraries
6) Convert to KMZ
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eTools: rec. ITU-R P.1546 calculationsPoint to Area
Very good agreement with P.1812 results in this case.
But results can change significantly!
P.1812 P.1546
Coverage analyses
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eTools: rec. ITU-R P.1546 calculations
Very different results from P.1812!
Interference analyses
P.1812
P.1546
Point to Area
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Use case: planning in Central America and Caribbean
eTools: CA_compat implements P.1546:• coverage analyses (wanted service area)• interference analyses
Terrain information considered only via effective antenna height
CA_Display: visualize compatibility analyses results and run detailed calculations
SLV
HND CNFS = 55.7 dB(μV/m)
FS = 21.9 dB(μV/m)
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eTools: Rec. ITU-R P.1812 Point to Pointfield strength calculation (terrain data).
Use case: planning in Central America and Caribbean
FS = 21.9 dB(μV/m) P.1546 no terrain
FS = 13.7 dB(μV/m) P.1812 terrainThis value would bring the margin to an acceptable level!!!
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Use case: GE84 planning activitieseTools: GE84Opt implements GE84 propagation curves for interference analyses.
Terrain information considered only via effective antenna height
FS(1%time,50%loc)GE84 curves = 66.19 – 37= 29.19 dB(mV/m)
87.7 MHzNon assignableAcceptable NFS54 (dB (μV/m))
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eTools: Rec. ITU-R P.1812 Point to Point field strength calculation (terrain data).
Use case: GE84 planning activities
Reduction of the interfering field due to terrain → ~13dB
87.7 MHz AAZANEN VS SIDI MEDJAHED
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Use case: GE84 planning activities
FS(1%temps,50%loc)GE84 curves = 66.19 – 37= 29.19 dB(mV/m)
Reduction of the interfering field due to terrain → ~13dBThis reduction would make the NFS acceptable for this interference situation! NFS with terrain profile = ~ 16 + 37 =~ 66 - 13 = 53 dB(mV/m).
eTools: GE84Opt implements GE84 propagation curves for interference analyses.
Terrain information considered only via effective antenna height
87.7 MHzNon assignableAcceptable NFS54 (dB (μV/m))
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Use case: FM coverage analyses
AZAANEN: P1812P2A Wanted FS = 54 dB(mV/m)
Field Strength dB(mV/m)
P.1812 P.1546