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
�