Recommendation ITU-R P.618¶

This Recommendation provides methods to predict the various propagation parameters needed in planning Earth-space systems operating in either the Earth-to-space or space-to-Earth direction.

Title	PDF	Latest approved in
Recommendation ITU-R P.618	[PDF]	2017-12
Propagation data and prediction methods required for the design of Earth-space telecommunication systems
Current recommendation version (In force)		Date
Recommendation ITU-R P.618-13	[PDF]	12/2017
Recommendations implemented in ITU-Rpy		Date
Recommendation ITU-R P.618-13	[PDF]	12/2017
Recommendation ITU-R P.618-12	[PDF]	07/2015
Recommendations not implemented in ITU-Rpy		Date
Recommendation ITU-R P.618-11	[PDF]	09/2013
Recommendation ITU-R P.618-10	[PDF]	10/2009
Recommendation ITU-R P.618-9	[PDF]	08/2007
Recommendation ITU-R P.618-8	[PDF]	04/2003
Recommendation ITU-R P.618-7	[PDF]	02/2001
Recommendation ITU-R P.618-6	[PDF]	10/1999
Recommendation ITU-R P.618-5	[PDF]	05/1997
Recommendation ITU-R P.618-4	[PDF]	10/1995
Recommendation ITU-R P.618-3	[PDF]	08/1994

Introduction¶

The propagation loss on an Earth-space path, relative to the free-space loss, is the sum of different contributions as follows:

attenuation by atmospheric gases;

attenuation by rain, other precipitation and clouds;

focusing and defocusing;

decrease in antenna gain due to wave-front incoherence;

scintillation and multipath effects;

attenuation by sand and dust storms.

Each of these contributions has its own characteristics as a function of frequency, geographic location and elevation angle. As a rule, at elevation angles above 10 degrees, only gaseous attenuation, rain and cloud attenuation and possibly scintillation will be significant, depending on propagation conditions.

Module description¶

itur.models.itu618.change_version(new_version)[source]¶

Change the version of the ITU-R P.618 recommendation currently being used.

This function changes the model used for the ITU-R P.618 recommendation to a different version.

Parameters:

new_version (int) –

Number of the version to use. Valid values are:

13: Activates recommendation ITU-R P.618-13 (12/17) (Current version)

12: Activates recommendation ITU-R P.618-12 (07/15) (Superseded)

itur.models.itu618.get_version()[source]¶

The version of the current model for the ITU-R P.618 recommendation.

Obtain the version of the ITU-R P.618 recommendation currently being used.

Returns:	version – The version of the ITU-R P.618 recommendation being used.
Return type:	int

itur.models.itu618.rain_attenuation(lat, lon, f, el, hs=None, p=0.01, R001=None, tau=45, Ls=None)[source]¶

Calculation of long-term rain attenuation statistics from point rainfall rate. The following procedure provides estimates of the long-term statistics of the slant-path rain attenuation at a given location for frequencies up to 55 GHz.

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points lon (number, sequence, or numpy.ndarray) – Longitudes of the receiver points f (number) – Frequency (GHz) el (sequence, or number) – Elevation angle (degrees) hs (number, sequence, or numpy.ndarray, optional) – Heigh above mean sea level of the earth station (km). If local data for the earth station height above mean sea level is not available, an estimate is obtained from the maps of topographic altitude given in Recommendation ITU-R P.1511. p (number, optional) – Percentage of the time the rain attenuation value is exceeded. R001 (number, optional) – Point rainfall rate for the location for 0.01% of an average year (mm/h). If not provided, an estimate is obtained from Recommendation Recommendation ITU-R P.837. Some useful values: 0.25 mm/h : Drizzle 2.5 mm/h : Light rain 12.5 mm/h : Medium rain 25.0 mm/h : Heavy rain 50.0 mm/h : Downpour 100 mm/h : Tropical 150 mm/h : Monsoon tau (number, optional) – Polarization tilt angle relative to the horizontal (degrees) (tau = 45 deg for circular polarization). Default value is 45 Ls (number, optional) – Slant path length (km). If not provided, it will be computed using the rain height and the elevation angle. The ITU model does not require this parameter as an input.
Returns:	attenuation – Attenuation due to rain (dB)
Return type:	Quantity

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf

itur.models.itu618.rain_attenuation_probability(lat, lon, el, hs=None, Ls=None, P0=None)[source]¶

The following procedure computes the probability of non-zero rain attenuation on a given slant path Pr(Ar > 0).

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points lon (number, sequence, or numpy.ndarray) – Longitudes of the receiver points el (sequence, or number) – Elevation angle (degrees) hs (number, sequence, or numpy.ndarray, optional) – Heigh above mean sea level of the earth station (km). If local data for the earth station height above mean sea level is not available, an estimate is obtained from the maps of topographic altitude given in Recommendation ITU-R P.1511. Ls (number, sequence, or numpy.ndarray, optional) – Slant path length from the earth station to the rain height (km). If data about the rain height is not available, this value is estimated automatically using Recommendation ITU-R P.838 P0 (number, sequence, or numpy.ndarray, optional) – Probability of rain at the earth station, (0 ≤ P0 ≤ 1)
Returns:	p – Probability of rain attenuation on the slant path (%)
Return type:	Quantity

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf

itur.models.itu618.site_diversity_rain_outage_probability(lat1, lon1, a1, el1, lat2, lon2, a2, el2, f, tau=45, hs1=None, hs2=None)[source]¶

Calculate the link outage probability in a diversity based scenario (two ground stations) due to rain attenuation. This method is valid for frequencies below 20 GHz, as at higher frequencies other impairments might affect affect site diversity performance.

This method predicts Pr(A1 > a1, A2 > a2), the joint probability (%) that the attenuation on the path to the first site is greater than a1 and the attenuation on the path to the second site is greater than a2.

Parameters:	lat1 (number or Quantity) – Latitude of the first ground station (deg) lon1 (number or Quantity) – Longitude of the first ground station (deg) a1 (number or Quantity) – Maximum admissible attenuation of the first ground station (dB) el1 (number or Quantity) – Elevation angle to the first ground station (deg) lat2 (number or Quantity) – Latitude of the second ground station (deg) lon2 (number or Quantity) – Longitude of the second ground station (deg) a2 (number or Quantity) – Maximum admissible attenuation of the second ground station (dB) el2 (number or Quantity) – Elevation angle to the second ground station (deg) f (number or Quantity) – Frequency (GHz) tau (number, optional) – Polarization tilt angle relative to the horizontal (degrees) (tau = 45 deg for circular polarization). Default value is 45 hs1 (number or Quantity, optional) – Altitude over the sea level of the first ground station (km). If not provided, uses Recommendation ITU-R P.1511 to compute the toporgraphic altitude hs2 (number or Quantity, optional) – Altitude over the sea level of the first ground station (km). If not provided, uses Recommendation ITU-R P.1511 to compute the toporgraphic altitude
Returns:	probability – Joint probability (%) that the attenuation on the path to the first site is greater than a1 and the attenuation on the path to the second site is greater than a2
Return type:	Quantity

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf

itur.models.itu618.scintillation_attenuation(lat, lon, f, el, p, D, eta=0.5, T=None, H=None, P=None, hL=1000)[source]¶

Calculation of monthly and long-term statistics of amplitude scintillations at elevation angles greater than 5° and frequencies up to 20 GHz.

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points lon (number, sequence, or numpy.ndarray) – Longitudes of the receiver points f (number or Quantity) – Frequency (GHz) el (sequence, or number) – Elevation angle (degrees) p (number) – Percentage of the time the scintillation attenuation value is exceeded. D (number) – Physical diameter of the earth-station antenna (m) eta (number, optional) – Antenna efficiency. Default value 0.5 (conservative estimate) T (number, sequence, or numpy.ndarray, optional) – Average surface ambient temperature (°C) at the site. If None, uses the ITU-R P.453 to estimate the wet term of the radio refractivity. H (number, sequence, or numpy.ndarray, optional) – Average surface relative humidity (%) at the site. If None, uses the ITU-R P.453 to estimate the wet term of the radio refractivity. P (number, sequence, or numpy.ndarray, optional) – Average surface pressure (hPa) at the site. If None, uses the ITU-R P.453 to estimate the wet term of the radio refractivity. hL (number, optional) – Height of the turbulent layer (m). Default value 1000 m
Returns:	attenuation – Attenuation due to scintillation (dB)
Return type:	Quantity

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf

itur.models.itu618.scintillation_attenuation_sigma(lat, lon, f, el, p, D, eta=0.5, T=None, H=None, P=None, hL=1000)[source]¶

Calculation of the standard deviation of the amplitude of the scintillations attenuation at elevation angles greater than 5° and frequencies up to 20 GHz.

Parameters:	lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points lon (number, sequence, or numpy.ndarray) – Longitudes of the receiver points f (number or Quantity) – Frequency (GHz) el (sequence, or number) – Elevation angle (degrees) p (number) – Percentage of the time the scintillation attenuation value is exceeded. D (number) – Physical diameter of the earth-station antenna (m) eta (number, optional) – Antenna efficiency. Default value 0.5 (conservative estimate) T (number, sequence, or numpy.ndarray, optional) – Average surface ambient temperature (°C) at the site. If None, uses the ITU-R P.453 to estimate the wet term of the radio refractivity. H (number, sequence, or numpy.ndarray, optional) – Average surface relative humidity (%) at the site. If None, uses the ITU-R P.453 to estimate the wet term of the radio refractivity. P (number, sequence, or numpy.ndarray, optional) – Average surface pressure (hPa) at the site. If None, uses the ITU-R P.453 to estimate the wet term of the radio refractivity. hL (number, optional) – Height of the turbulent layer (m). Default value 1000 m
Returns:	attenuation – Attenuation due to scintillation (dB)
Return type:	Quantity

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf

itur.models.itu618.rain_cross_polarization_discrimination(Ap, f, el, p, tau=45)[source]¶

Calculation of the cross-polarization discrimination (XPD) statistics from rain attenuation statistics. The following procedure provides estimates of the long-term statistics of the cross-polarization discrimination (XPD) statistics for frequencies up to 55 GHz and elevation angles lower than 60 deg.

Parameters:	Ap (number, sequence, or numpy.ndarray) – Rain attenuation (dB) exceeded for the required percentage of time, p, for the path in question, commonly called co-polar attenuation (CPA) f (number) – Frequency el (number, sequence, or numpy.ndarray) – Elevation angle (degrees) p (number) – Percentage of the time the XPD is exceeded. tau (number, optional) – Polarization tilt angle relative to the horizontal (degrees) (tau = 45 deg for circular polarization). Default value is 45
Returns:	attenuation – Cross-polarization discrimination (dB)
Return type:	Quantity

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf

itur.models.itu618.fit_rain_attenuation_to_lognormal(lat, lon, f, el, hs, P_k, tau)[source]¶

Compute the log-normal fit of rain attenuation vs. probability of occurrence.

Parameters:

lat (number, sequence, or numpy.ndarray) – Latitudes of the receiver points
lon (number, sequence, or numpy.ndarray) – Longitudes of the receiver points
f (number or Quantity) – Frequency (GHz)
el (sequence, or number) – Elevation angle (degrees)
hs (number, sequence, or numpy.ndarray, optional) – Heigh above mean sea level of the earth station (km). If local data for the earth station height above mean sea level is not available, an estimate is obtained from the maps of topographic altitude given in Recommendation ITU-R P.1511.
P_k (number) – Rain probability
tau (number, optional) – Polarization tilt angle relative to the horizontal (degrees) (tau = 45 deg for circular polarization). Default value is 45

Returns:

sigma_lna – Standar deviation of the lognormal distribution
m_lna – Mean of the lognormal distribution

References

[1] Propagation data and prediction methods required for the design of Earth-space telecommunication systems: https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.618-12-201507-I!!PDF-E.pdf