Wireless Challenges
Everybody involved in the field of "Wireless"
is aware of this sometimes stubborn transmission media "Radio Channel."
But more than this. The resource "Radio Spectrum" is rare and became very expensive recently. European mobile communication network operators have spent more than 100 Billion Euro solely for licensing some tens of Megahertz of radio spectrum for their new mobile systems known as UMTS. The design of every new system is a large investment which should consider the radio conditions realistically right from the beginning.
Many things get into motion by the advent of new principles in wireless communications engineering: "The bad channel is the good channel" is a citation by J. Bach Andersen, a pioneer of European mobile communications research, illustrating the new views on multipath propagation feasible by modern array and signal processing technologies.