In: Resources 29 Aug 2014 Tags: , , , , , , ,

Definitions:

Mechanical Tilt
. The downtilt angle varies over the horizontal beamwidth. Patterns
measured ±90° from the center of the beam have decreasing
tilt angle until there is no tilt 90° from the main beam.
. The horizontal half-power beam width increases with greater
downtilt angle.
. The resulting gain reduction depends on azimuth direction.

TiltM

Electrical Tilt
. There is uniform downtilt over the whole azimuth range.
. The horizontal half-power beamwidth is independent of the
downtilt angle.
. There is identical gain reduction in all azimuth directions.

TiltE

 

TiltEM

In: Products, Resources 16 Jun 2014 Tags: , , , ,

To create the Standard-RM propagation model that is faithful to Fresnel’s theory (for frequencies > 30 MHz), it took more than 20 years of research and development and more than 50 iterations of implementation in our software, which has been verified with hundreds of thousands of measurements.

Standard-RM includes the Fresnel complex integral, diffraction (2D and 3D), Ducting, Troposcattering, Climate, Reflections, Refraction, Scattering…

 

Since 1988, we there have been many different methods for calculating diffraction that we have implemented in our software (Epstein Peterson, Bullington and Deygout). All these methods have one thing in common: they do not take into account the effects of multiple paths that sum together at a given point at a given frequency.  This aspect can be accounted for in various ways as in the following models:

  • Propagation curves CCIR/ITU (370, 1546) with the notion of effective height
  • Okumura-Hata with the notion of effective height
  • Wojnar or Deygout (94) with FPL (fourth-power law)
  • Durkin (with the slope factor corrections altering the fundamental model)
  • Two-ray plane earth models
  • Longley Rice (ITM)
  • Delta-Bullington
  • Etc.

 

Recommendation ITU-R P.526-13 offers a method of calculating diffraction “sub-path”, inspired by our different models. In this model, the Fresnel integral treated approximately so it is incomplete, however, it demonstrates that when calculating propagation deterministically, that the Fresnel model is important.

 

2014 ATDI integrates its model RM-Standard in its software ICS and HTZ.

The version released yet incorporates so far FPL + Deygout diffraction, and we only use this to determine the minimum attenuation. Once we have finished checking the new model with measurements, it will become redundant.

 

This model is entirely dependent on the input data: model quality and accuracy of emission and reception parameters. We noticed that unlike most models which are more “permissive”, an approximate antenna pattern greatly reduces the correlation. In addition, its sensitivity to the accuracy of terrain data requires new cartographic data, including the need to calculate attenuation due to vegetation with an absorption model.

 

In conclusion, this model does not give “better” results than another, if it is used with data of moderate quality. It is faithful to the physics of waves. Used with qualified data, we have observed a standard deviation of error <2.5 dB instead of 3.2 / 3.4 dB with previous implementations.

 

Advantages:

  • End of approximations!
  • A pure model faithful to the geometry of the terrain
  • Allow the true validation of the parameters of a plan

 

Disadvantages:

  • Very long computation time
  • Requires an accurate and reliable terrain model
  • Requires the actual station parameters

 

Applications:

  • Propagation prediction above 30 MHz
  • A reference model for comparison

 

Base model:

Fresnel Integrals
Diffraction (GTD, 2D, 3D)
Subpath switching (for compatibility with all the diffraction methods)

Support:

Troposcattering
Ducting (multi-layers)
Mixed path
Gaz attenuation
Rain attenuation
Slant path
Scattering
Absorption
Reflection (2D, 3D)
Gradient
Fog
Snow
Clutters and buildings (flat attenuations, dB/km attenuations, mixed diffraction/absorption…)

Outdoor, Outdoor/Indoor, Indoor, 2D 1/2 and 3D terrain models
Coverage calculation, Point to Point and Point to Multi-Points, Path budget
Clutter tuning

Avalaible in ICS telecom, ICS designer, ICS LT and HTZ

 

 

The Standard-RM model will soon be released (both formulas and method). Check for further announcements on our website

header_icstelecom_9

In: Resources 24 Feb 2014 Tags: ,

Every month, ATDI compares different propagation models for a given service based on very accurate measurements.

 

This month, WIMAX

Last Episode: FM

 

Propagation model versus Artistic vision

Rule #1:  a propagation model must be reversible (A->B = B->A)

 

Test LOS:

ProfileReverse

Parameters:

. Tx/Rx antenna height (A): 10 m (AGL) 863 m (ASL)

. Rx/Tx antenna height (B): 10 m (AGL)  228 m (ASL)

. Tx power 10 W (EIRP)

. Distance: 22.678 km

. Type of path: LOS (line of sight) – Subpath free – Clutter class: Open

. Frequency: 900 MHz

 

Model-Episode2