The depth of the resulting fading of the signal is very
dependent on whether a strong line-of-sight path exists between transmitter and
receiver, in which case the fading signal envelope usually conforms to a Ricean statistical distribution, whereas the line-of-sight
path is obscured, and energy arrives at the receiver by a large number of reflections,
then a Rayleigh distribution of the envelope level is more
likely to occur. The characteristics of the fading signal envelope make a significant
impact on the bit error rate performance for a digital communications link. An excellent
book on multipath fading is Jakes (1993), and a very thorough text on the performance of
data modems in fading is given in Proakis (1989).
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