The spatial correlation of shadow fading in macrocellular mobile radio systems

It is conventional to refer to three distance scales of channel variation in mobile radio systems, namely multipath or fast fading, shadowing or slow fading, and range variation. Of these, the least studied has been the shadowing, which is the variation of the local mean signal strength (averaged over the fast fading) at a fixed range. The shadowing variation is statistically characterised by its distribution (approximately lognormal) and its standard deviation (5-10 dB depending on the environment and frequency). Some studies have shown that shadowing is a deterministic effect, caused by variation in the physical environment, yet very little is known about its spatial distribution or correlations. These parameters would be extremely useful for system simulation and design, leading to a better understanding of the propagation channel and to system designs of higher integrity.