Coded Orthogonal Frequency Division Multiplexing - (COFDM) - This type of modulation can transmit many streams of data simultaneously, each one occupying only a small portion of the total available bandwidth.  It can work well in areas where obstacles would otherwise distort digital transmission.  COFDM is more prevalent as an European MMDS and terrestrial transmission. (2002 definition.)  Also see http://en.wikipedia.org/wiki/COFDM.