The Empirical Formulation Of Radio Wave Propomentation Models

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General definition:
• They are empirical mathematical formulation for the characterization of radio wave propagation as a function of frequency, distance and other conditions.
• These models predict the path loss (i.e. the reduction in power density of an electromagnetic wave as it propagates through space or underground) of a transmitter and also the effective coverage area of transmitter.
We know that when a signal travels from a wireless channel, it undergoes various types of Propagation Effects like – Reflection, Diffraction and Scattering because of the presence of obstructions like buildings, mountains, hills etc.
Reflection is when the EM waves encroach on objects that are greater than the wavelength
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-It is very practical and is used in Japan in Modern Land Mobile Radio Systems.
• Demerits of this model:
-It has a slow response for rapid changes in terrain. Thus, it is fairly good in urban and sub urban areas but it is not so good in rural areas.
3. Hata model:
• This model is an Empirical Formulation of graphical path loss data that is given by Okumura.
• Its frequency range is 150 MHz – 1500 MHz.
• Its formulation is limited to only certain ranges of input parameters.
• Its formulations are applicable only for quasi smooth terrain.
• The mathematical expression is as follows : L (db) = 69.55 + 26.16fc - 13.82loghte - a (hre) + (44.96.55loghte) log10d
Carrier frequency: 150MHz≤ fc ≤1500MHz
Base station antenna height (hte): 30m ≤ hb ≤ 200m
Mobile unit antenna height (hre): 1m ≤ hm ≤ 10m
Transmission distance (d):1km≤ d ≤ 20 km
• The formulas have enhanced the practical value of Okumura Method but they do not include any path specific corrections.
• This model approximates the Okumura model for distances d > 1 Km. Thus; it is a good model for first generation cellular systems.
4. Cost 231

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