  The fundamental phenomenon widely known as multipath is unavoidable in
wireless communication, and affects almost every element of modern wireless
communication systems. The impact of multipath on the received signal depends
on whether the delay spread (i.e., spread of time delays associated with
different multipath components) is large or small relative to the signalling
period of the wireless communication system. In narrowband systems, the delay
spread is about one tenth (or less) of the signalling period. The delay spread
and the signalling period of broadband systems are in the same order of
magnitude. In between these two extremes, there appears to exist an important,
yet overlooked, class of systems whose delay spread is neither small nor large
enough for them to fall into these two basic classes. In this paper, the effect
of multipath on this class of systems denoted henceforth as mediumband is
studied, and its channel is characterized in compact form in order to enable
future research into this class of wireless communication systems.
