Diversity embedded space-time code from quasi-orthogonal designs

This paper proposes a class of space-time (ST) codes for supporting applications that demand unequal error protection. Traditionally, an ST code is designed to support a single information stream aiming to achieve a point on the fundamental rate versus diversity trade-off curve. The construction in this paper is based on the diversity-embedded codes recently proposed by Diggavi et.al., where-in ST codes need to encode multiple information streams, with each stream demanding a different level of reliability. In this paper, we propose to use an existing class of ST codes with low maximum-likelihood decoding complexity, as diversity embedded codes. For this class of codes, we are able to characterize the different diversity levels achievable for every message symbol.