A view on full-diversity modulus-preserving rate-one linear space–time block codes

Abstract

In this paper, we consider the class of linear space time block codes (STBCs) that possess the following properties: (i) enabling full antenna diversity, (ii) preserving the modulus of information symbols, and (iii) achieving the maximum rate of one symbol per channel use under (i) and (ii). We first provide an alternative construction for full-diversity rate-one STBCs that are based on linear constellation precoding (LCP). In sharp contrast to existing LCP-based designs, the proposed construction is modulus-preserving, thanks to an explicit unitary diagonal precoding on symbol blocks combined with an implicit fast-Fourier-transform (FFT) precoding via circularly shifted transmissions over multiple antennas. Our proposed construction also allows flexible choices on the precoder size, a feature not available in the original design. We then demonstrate that quasi-orthogonal (QO) STBCs can be constructed by embedding modulus-preserving LCP designs into orthogonal structures. Interestingly, QO-STBCs can be interpreted as space–time–frequency (STF) block codes, that were originally developed for multi-antenna multi-carrier systems, up to FFT transformations.