Construction of Structured LaST Codes

Abstract

The objective of this paper is to present constructions of space-time (ST) codes that are endowed with energy efficient constellations, resulting in good performance at finite values of signal-to-noise ratios (SNR). This problem is especially relevant since codes that achieve the diversity-multiplexing gain (D-MG) tradeoff, a metric of performance at high values of SNR, have been recently proposed for arbitrary number of transmit and receive antennas. We provide a technique for constructing structured lattice space-time codes derived from dense lattice packings, where constellation shaping is achieved through a nested lattice (Voronoi) construction and sphere encoding. Applying this technique to ST codes derived from cyclic division algebras, we construct codes that achieve the D-MG tradeoff over every fading channel (i.e., are approximately universal) and have excellent performance at finite SNRs. A host of simulation results using a low complexity MMSE-GDFE lattice decoder are presented