Multi-Dimensional Constellations for Coded Transmission in Fading Channels

In high data rate OFDM systems, channel diversity can be a major concern. We revisit multi-dimensional constellation design, or short block spreading, and propose several improvements: a fine tuned Chernoff bound, a full optimization using Givens rotations, and a reduced complexity algorithm that exploits symmetry without loss of optimality. In fact, the problem´s complexity increases exponentially with number of dimensions, and previously proposed algorithms are either sub-optimal or incomplete. We also present a new interleaver scheme that continuously, and possibly adaptively, shuffles the sub-carrier grouping. Some of the ideas can be extended to the design of Space Time Codes.