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Introduction
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The ITU propagation
model P.1546
model is used for point-to-area radio propagation predictions for
terrestrial services in the frequency range of 30 MHz to 3000 MHz.
It is intended for use
- on tropospheric radio
circuits over land paths, sea paths and/or mixed land-sea paths
- between 1 km and 1000 km
length
- for effective transmitting
antenna heights less than 3000 m.
The method is based on
interpolation/extrapolation from empirically derived field strength
curves as functions of distance, antenna height, frequency and
percentage of time. The calculation procedure also includes corrections
of the results obtained from this interpolation/extrapolation to
account for terrain clearance and terminal clutter obstructions.
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Field strength curves for
different transmitter heights
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The propagation curves represent field strength values
for 1 kW effective radiated power (ERP) at nominal frequencies of 100,
600 and 2000 MHz, respectively, as a function of various parameters;
some curves refer to land paths, others refer to sea paths.
The curves are based on measurement
data mainly relating to mean
climatic conditions in temperate regions containing warm seas, e.g. the
Mediterranean Sea. The land-path curves were prepared from data
obtained mainly from temperate climates as encountered in Europe and
North America. The sea-path curves were prepared from data obtained
mainly from the Mediterranean Sea regions.
The model takes account of the
effective height of the transmitting/base antenna, which is the height
of the antenna above terrain height averaged between distances of 3 km
to 15 km in the direction of the receiving/mobile antenna.
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Parameters
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The two parameters to be defined
by the user with their
range:
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In this ITU recommendation, and
generally, location variability refers to the spatial statistics of
local ground cover variations. Thus for a land receiving/mobile antenna
location the field strength E which will be exceeded for q% of
locations is given by:
where:
Qi (x): inverse complementary cumulative normal
distribution as a function of probability
σL:
standard deviation of the Gaussian distribution of the local means in
the study area
Values of standard deviation
are dependent on frequency and environment, and empirical studies have
shown a considerable spread.
The propagation curves
represent the field strength values exceeded for 1%, 10% and 50% of
time. Other values will be interpolated. This model is not valid for
field strengths exceeded for percentage times outside the range from 1%
to 50%.
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Example
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The example show two predictions of the received
power with the ITU P.1546 model. The prediction area covers the
soutwest of Germany (south of Stuttgart).
Two DAB transmitters, mounted on very tall towers (see figures on the
left), are
located in the area.
The predictions are shown below and can be enlarged by clicking on the
figures.
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Clutter/Morpho database
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Rx power of DAB transmitter (Stuttgart)
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Rx power of DAB transmitter (Raichberg)
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Brochure with all rural prediction models.
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Comparison between different rural prediction
models.
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Overview all rural prediction models.
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TV tower in Stuttgart
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Broadcasting Tower on the Raichberg
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