Annex 1
1 Introduction
2 Interference propagation
mechanisms
3
Clear-air interference prediction
3.1
General comments
3.2
Deriving a prediction
3.2.1 Outline of the procedure
Step 1: Input data
Step 2: Selecting average year or worst-month prediction
Step 3: Radiometeorological data
Large bodies of inland water
Large inland lake or wet-land areas
Effective Earth radius
Step 4: Path profile analysis
Step 5: Calculation of propagation predictions
4
Clear-air propagation models
4.1
General
4.2
Line-of-sight propagation (including short-term effects)
4.3
Diffraction
4.4
Tropospheric scatter (Notes 1 and 2)
4.5
Ducting/layer reflection
4.6
Additional clutter losses
4.6.1 General
4.6.2 Clutter categories
4.6.3 The height-gain model
4.6.4 Method of application
4.7
The overall prediction
4.7.1 Trans-horizon paths
4.8
Calculation of transmission loss
5
Hydrometeor-scatter interference prediction
5.1
Introduction
5.2
Input parameters
5.3
The step-by-step procedure
Step 1: Determination of meteorological parameters
Step 2: Conversion of geometrical parameters to plane-Earth representation
Step 3: Determination of link geometry
Step 4: Determination of geometry for antenna gains
Step 6: Attenuation outside the rain cell
Step 7: Numerical integration of the scatter transfer function
Numerical integration: There are
many methods available for numerical integration, and numerous mathematical
software packages include intrinsic integration functions which can be
exploited effectively. Where the user wishes to develop a dedicated package in
other programming languages, methods based on iterative bisection techniques
have proved effective. One such technique is the Romberg method, which is a
higher-order variant of the basic trapezoidal (i.e. Simpson’s) rule for
integration by successive bisections of the integration intervals.
The extended trapezoidal rule
Step 8: Determination of other loss factors
Step 9: Determination of the cumulative distribution of transmission loss
Appendix 1 to Annex 1
Radio-meteorological data required for the clear-air prediction
procedure
1
Introduction
2
Maps of vertical variation of radio
refractivity data
3
Map of surface refractivity, N0
4
Implementation of maps in computer database form
Appendix 2 to Annex 1 Path profile
analysis
1
Introduction
2
Construction of path profile
3
Path length
4
Path classification
4.1
Classification Step 1: Test for a trans-horizon path
4.2
Step 2: Test for line-of-sight with sub-path
diffraction (i.e. without full first Fresnel zone clearance)
5
Derivation of parameters from the path profile
5.1
Trans-horizon paths
5.1.1 Interfering antenna horizon
elevation angle, θt
5.1.2 Interfering antenna horizon
distance, dlt
5.1.3 Interfered-with antenna horizon
elevation angle, θr
5.1.4 Interfered-with antenna horizon
distance, dlr
5.1.5 Angular distance θ (mrad)
5.1.6 “Smooth-Earth” model and effective
antenna heights
Appendix 3 to Annex 1 An
approximation to the inverse cumulative normal distribution function for x £ 0.5