L = 32.4 log10() + 20 log10(d) (2.22) where f is the frequency in megahertz and d is the distance in kilometres. In reality the radio wave propagation path is normally a non-line-of-sight situation with surrounding obstacles like buildings and trees. Therefore the applicability of the free space propagation loss is limited. The received signal actually consists of several components, which have been travelling through different paths facing reflection, diffraction and scattering. This effect is called multipath and one component represents one propagation path. The different components, signal vectors, are summarised as one signal considering the vector phases and amplitudes. The attenuation of the radio wave signal power depends on the frequency band and terrain types between the transmitting and receiving antenna. When estimating the total path loss of the radio signal, Radio Wave Propagation the travelled path can be split into sections according to terrain types. As the propagation varies according to the area type, this has to be taken into account in the propagation model. The difference can be explained using the measured correction factor for each terrain type. One more phenomenon of the mobile environment is the different fading types. Slow fading happens when the radio wave signal is diffracted due to buildings or other big obstacles in the signal path. The receiver, the mobile phone, is in a way in the shadow of these obstacles. Slow fading is log-normal fading and therefore modelled with a Gaussian distribution. The previously mentioned multipath propagation causes short term fades, which can be relatively deep, in the received signal due to the summarised signal vectors, which are having different phases and amplitudes. This fading is known as fast fading or Rayleigh fading. As the second name implies, fast fading can be modelled using the Rayleigh distribution. The third fading type is a combination of the previous two and is called Rician fading. When speaking about fast fading only the scattered c