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A17.2 A17.2

This model describes the theoretical minimum propagation path loss achievable in free space conditions. This model is appropriate to use on paths were unobstructed direct-Line-of-Sight propagation could be expected (e.g. point-to-point fixed service links, links over short distances in open areas, etc). 

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F470 F470

Figure 470: SEAMCAT Interface to the free space propagation model

For free space {XE "Propagation model:Free space" } space  model the path loss is defined by:

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body $L=32.4+10{{\log }_{10}}\left( {{\left( \frac{\left( {{h}_{tx}}-{{h}_{rx}} \right)}{1000} \right)}^{2}}+d_{{}}^{2} \right)+20{{\log }_{10}}f$

  (Eq. 189)

comment: 

the equation has been modified

- According to Rec. ITU-R P.525 32.44 -> 32.4

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The variations correspond to the standard deviation variations.

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Figure 471 illustrates when the variation is disabled (i.e. no std).

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F471 F471

Figure 471: Example of the vector events of the Free Space when Variation is disabled
(i.e. equivalent to σ = 0 dB) active (i.e. mean = 91.52 dB)

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Figure 472 presents the Free Space when Variation is activated (std = σ = 2.5 dB). The value presented in Figure 471 and Figure 472 are extracted with the following parameters: f = 900 MHz, d =  1 km, h_tx = h_rx = 10 m.

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F472 F472

  Example of Free Space results when the Variation (i.e. σ = 2.5 dB) is active 

(i.e. mean = 91.52 dB)