Theory behind model

The model is simply a variation of the log-distance path-loss model so as to account for loss compensation due to diffraction and also for losses due to the orientation of the antenna. The log-distance path-loss model was chosen as a foundation because of its prevalent application in outdoor terrain modeling. The partition based model was not considered for cell sites because of assumption 4 and also because of the complexity involved in estimating the number of obstacles in the path of a wave from the Antenna to the point being considered. The equation of the model used is given in equation 1. A brief description of how it was derived is given thereafter.

 

 

 

 

                            Equation 1. Propagation model

 

Where,

1. ‘Pr’ is the received power

2. ‘EIRP’ is the effective isotropic radiated power. (Pt.Gt)

3. ‘Gr’ is the receiver gain.

4. ‘λ’ is the wavelength.

5. ‘d’ is the distance of the point under consideration from the       antenna.

6. ‘K’ is the diffraction ‘index’ for the given cell site based on terrain. DO NOT CONFUSE THIS WITH THE COEFFICIENT OF DIFFRACTION

7. ‘w’ is the approximate number of diffractions experienced from antenna to a given point.

8. ‘N’ is the path loss exponent which is to be determined

 

Alternatively, equation 1 may be expressed as equation 2 (making sure all powers are in mW and all lengths are in meters)

 

 

 

                Equation 2. Propagation model (alternative form)

 

To account for antenna orientations, the same equation is used with a different path loss coefficient for regions experiencing higher antenna gain (for convenience these are two regions conical in shape back to back with their pointed ends at the antenna location, the axis of the cones lying at the azimuth).