Method and apparatus for maintaining independent, parallel data streams over separate modulation channels of a multi-dimensional modulator

A method and apparatus are provided for supporting the transmission of communications data in a satellite communications network 10 between user terminals 15-18 and a ground station 14 via a satellite 12 . At least one carrier signal is generated in a beam spot and conveys communications data over at least one downlink 22-25 to the user terminals 15-18 . The carrier signal is modulated simultaneously with independent communications data streams EDP 15 and EDP 18 over modulation channels 802 and 804 , respectively, of a multi-dimensional modulator 400 . By passing independent data streams over each dimension of an n-dimension modulation technique, different encoding schemes may be assigned to user terminals 15-18 based upon the strength of the signal received by the user terminal 15-18.