Sparse Superimposed Coding Based on Index Redefinition
Xuewan Zhang, Dalong Zhang
Abstract
Sparse superimposed coding (SSC) is a promising coding technique to achieve high reliability and low latency for short packet communications. To further improve its performance, an index redefinition-based SSC (IR-SSC) is proposed, in which the sparse vector can represent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> index bit streams and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> modulation bit streams. The index redefinition is introduced to avoid index collisions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> index bit streams. Meanwhile, constellation rotation-based constellations are adopted as modulation constellations for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> modulation bit streams and as identification tags of these <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> index bit streams. Correspondingly, a constellation matching-based multipath matching pursuit decoder is designed to recover the order of these <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> index bit streams and to decode all transmitted bits. Simulation results show that the proposed IR-SSC scheme can improve both the reliability and latency performance, compared with conventional SSC schemes.