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).
Figure 465: SEAMCAT Interface to the free space propagation model
For free space model the path loss is defined by:
(Eq. 180)
The variations correspond to the standard deviation variations.
Note: The Free space model allows the possibility to include some variations in the similar manner as it is done for all other built-in models. If user wants to use just the median theoretical value, the variations option should be disabled.
Figure 466 illustrates when the variation is disabled (i.e. no std).
Figure 466: 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)
Figure 467 presents the Free Space when Variation is activated (std = σ = 2.5 dB). The value presented in Figure 466 and Figure 467 are extracted with the following parameters: f = 900 MHz, d = 1 km, htx = hrx = 10 m.