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 125-15 500 MHz for aeronautical and satellite 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.
| Variable | Type | Units | Limits | Description |
|---|---|---|---|---|
d__km |
double | km | 0 <= d__km |
Path distance between terminals |
h_1__meter |
double | meter | 1.5 <= h_1__meter |
Height of the low terminal |
h_2__meter |
double | meter | 1.5 <= h_2__meter |
Height of the high terminal |
f__mhz |
double | MHz | 125 <= f__mhz <= 15 500 |
Frequency |
time_percentage |
double | 0.01 <= time_percentage <= 0.99 |
Time percentage |
Outputs to P.528 are contained within a defined Results structure.
| Variable | Type | Units | Description |
|---|---|---|---|
d__km |
double | km | Path distance. Could be slightly different than specified in input variable if within LOS region |
A__db |
double | dB | Total path loss |
A_fs__db |
double | dB | Free space path loss |
propagation_mode |
int | Mode of propagation.
|
Possible return codes, including the corresponding defined constant name as defined in p528.h:
| Value | Const Name | Description |
|---|---|---|
| 0 | SUCCESS |
Successful execution |
| 1 | ERROR_VALIDATION__D_KM |
Path distance must be >= 0 km |
| 2 | ERROR_VALIDATION__H_1 |
Low terminal height must be >= 1.5 meters |
| 3 | ERROR_VALIDATION__H_2 |
High terminal height must be >= 1.5 meters |
| 4 | ERROR_VALIDATION__TERM_GEO |
Low terminal must be <= high terminal height |
| 5 | ERROR_VALIDATION__F_MHZ_LOW |
Frequency must be >= 125 MHz |
| 6 | ERROR_VALIDATION__F_MHZ_HIGH |
Frequency must be <= 15 500 MHz |
| 7 | ERROR_VALIDATION__PERCENT_LOW |
Time percentage must be >= 0.01 |
| 8 | ERROR_VALIDATION__PERCENT_HIGH |
Time percentage must be <= 0.99 |
| 10 | ERROR_HEIGHT_AND_DISTANCE |
Terminals are occupying the same point in space (they are the same height and 0 km apart) |
| 0xFF1 | WARNING__DFRAC_TROPO_REGION |
Warning that the diffraction and troposcatter model may not be physically consistent with each other. Caution should be taken when using the result |
| 0xFF2 | WARNING__LOW_FREQUENCY |
Warning that the entered frequency is less than the lower limit specified in P.528. Caution should be taken when using the result |
Note: Return codes over 0xFF0 signify warnings occured in the calculation. Use bitwise OR operations to diagnosis, as more than one warning could be possible.
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 |
time_percentage |
A__db |
|---|---|---|---|---|---|
| 15 | 10 | 1 000 | 500 | 0.5 | -110.0 |
| 100 | 100 | 15 000 | 3 600 | 0.9 | -151.2 |
| 1 500 | 15 | 10 000 | 5 700 | 0.1 | -299.5 |
- 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.
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 2017 project file is provided for Windows users to support the build process and configuration.
The .NET support of P.528 consists of a simple pass-through wrapper around the native DLL. It is compiled to target .NET Framework 4.7.2. Distribution and updates are provided through the published NuGet package.
For questions, contact Billy Kozma, (303) 497-6082, wkozma@ntia.gov