Space-Time Codes from Structured Lattices

TL;DR

This paper introduces lattice-based space-time codes optimized for short and large block lengths, achieving optimal diversity-multiplexing tradeoff and practical decoding efficiency for MIMO channels.

Contribution

It presents novel lattice and trellis-based space-time code constructions with optimal tradeoffs and reduced decoding complexity, applicable to various block lengths.

Findings

Codes achieve optimal diversity-multiplexing tradeoff.

Perform well at moderate SNR levels.

Comparable performance to state-of-the-art codes with similar complexity.

Abstract

We present constructions of Space-Time (ST) codes based on lattice coset coding. First, we focus on ST code constructions for the short block-length case, i.e., when the block-length is equal to or slightly larger than the number of transmit antennas. We present constructions based on dense lattice packings and nested lattice (Voronoi) shaping. Our codes achieve the optimal diversity-multiplexing tradeoff of quasi-static MIMO fading channels for any fading statistics, and perform very well also at practical, moderate values of signal to noise ratios (SNR). Then, we extend the construction to the case of large block lengths, by using trellis coset coding. We provide constructions of trellis coded modulation (TCM) schemes that are endowed with good packing and shaping properties. Both short-block and trellis constructions allow for a reduced complexity decoding algorithm based on minimum mean squared error generalized decision feedback equalizer (MMSE-GDFE) lattice decoding and a combination of this with a Viterbi TCM decoder for the TCM case. Beyond the interesting algebraic structure, we exhibit codes whose performance is among the state-of-the art considering codes with similar encoding/decoding complexity.