APPLICABILITY OF 4-DIMENSIONAL MODULATIONS TO DIGITAL SATELLITES - A SIMULATION STUDY

We examine multidimensional modulation schemes in view of their applic ation to digital satellite communications systems. In particular, we f ocus our attention on four-dimensional signals and describe the applic ability of several coded constellations based on Q(2)PSK with optimum selection of baseband signals. Equal-energy signal sets, signals carve d from lattices, convolutionally-encoded and trellis-encoded schemes a re compared by evaluating their performance by computer simulation in a channel model that includes the effects of linear filters, nonlinear amplifiers, and carrier and timing recovery circuits. Among the schem es considered here, trellis-coded modulation seems to offer the best t radeoff between performance and complexity.