Talk:Prediction models

Untitled
Tried to improve the appearance of the later equations. Removed the original poster's warning, "NOT FINALIZED, I HAVE PROBLEMS FORMATTING THE EQUATIONS", but somebody with more knowledge than I should check the equations for errors or more conventional formatting. Kevinz 19:26, 5 March 2007 (UTC)

Free Space
The free space path loss model is usually the reference point from which all propagation models are employed and is used for determining free-space path loss. It is based on a $$1/R^2$$ or 20-dB/decade path loss. The following equation shows the free-space or Friis equation: $$\frac{P_R}{P_T}=G_TG_R\left(\frac{\lambda}{4\pi d}\right)^2$$    Equation  1.1


 * where
 * $$P_R$$ = power available at the receiving antenna
 * $$P_T$$ = power supplied from the transmitting antenna
 * $$G_R$$ = receiving antenna gain
 * $$G_T$$ = transmitting antenna gain
 * $$d$$ = distance between two antennas in free space.
 * $$\lambda$$ = wavelength

Since loss is generally expressed in dB, Equation 1.1 can be written as:

$$L_f= 32.4 + 20\log(d) + 20\log(f_c)\,$$ Equation 1.2


 * where
 * $$L_f$$ = free space path loss, in dB
 * $$d$$ = distance, in km
 * $$f_c$$ = carrier frequency, in MHz

For 900 MHz and 1800 MHz equation 1.2 can be reduced to the form: $$L_f = A + B\log(d)$$, where A is the path loss at 1km and B is the slope:

$$L_{f_{900}} = 91.5+20\log(d)\,$$

$$L_{f_{1800}} = 97.5+20\log(d)\,$$