Recommendation ITU-R P.528-5 - U.S. Reference Implementation

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This code repository contains the U.S. Reference Software Implementation of Recommendation ITU-R P.528. This Recommendation contains a method for predicting basic transmission loss in the frequency range 100-30 000 MHz for aeronautical services. The software implements Annex 2 of Rec P.528, the Step-by-Step method to computing propagation loss for air-to-ground paths.

Companion software (p528-gui) provides a Graphical User Interface (GUI) that can be used with this software implementation.

Inputs

Variable	Type	Units	Limits	Description
d__km	double	km	0 <= d__km	Great circle path distance between terminals
h_1__meter	double	meter	1.5 <= h_1__meter <= 20 000	Height of the low terminal
h_2__meter	double	meter	1.5 <= h_2__meter <= 20 000	Height of the high terminal
f__mhz	double	MHz	100 <= f__mhz <= 30 000	Frequency
T_pol	int			Polarization 0 = Horizontal 1 = Vertical
time	double		1 <= time <= 99	Time percentage

Outputs

Outputs to P.528 are contained within a defined Results structure.

Variable	Type	Units	Description
d__km	double	km	Great circle path distance. Could be slightly different than specified in input variable if within LOS region
A__db	double	dB	Basic transmission loss
A_fs__db	double	dB	Free space basic transmission loss
A_a__db	double	dB	Median atmospheric absorption loss
theta_h1__rad	double	rad	Elevation angle of the ray at the low terminal
propagation_mode	int		Mode of propagation 1 = Line of Sight 2 = Diffraction 3 = Troposcatter
warnings	int		Warning flags

Error Codes and Warning Flags

P.528 supports a defined list of error codes and warning flags. A complete list can be found here.

Example Values

The below table includes a select set of example inputs and outputs for testing purposes. The P.528 CSV data files contain an extensive set of validation example values.

d__km	h_1__meter	h_2__meter	f__mhz	T_pol	time	A__db
15	10	1 000	500	0	50	110.0
100	100	15 000	3 600	0	90	151.6
1 500	15	10 000	5 700	0	10	293.4
30	8	20 000	22 000	1	50	151.1

Notes on Code Style

• In general, variables follow the naming convention in which a single underscore denotes a subscript (pseudo-LaTeX format), where a double underscore is followed by the units, i.e. h_1__meter.
• Variables are named to match their corresponding mathematical variables in the underlying Recommendation text.
• Wherever possible, equation numbers are provided. It is assumed that a user reviewing this source code would have a copy of the Recommendation's text available as a primary reference.

Configure and Build

C++ Software

The software is designed to be built into a DLL (or corresponding library for non-Windows systems). The source code can be built for any OS that supports the standard C++ libraries. A Visual Studio 2019 project file is provided for Windows users to support the build process and configuration.

C#/.NET Wrapper Software

The .NET support of P.528 consists of a simple pass-through wrapper around the native DLL. It is compiled to target .NET Framework 4.8. Distribution and updates are provided through the published NuGet package.

References

• Recommendation ITU-R P.528
• Rec ITU-R P.528 GUI

Contact

For questions, contact Billy Kozma, (303) 497-6082, wkozma@ntia.gov