New Diversity-Embedding STBC Constructions

Abstract

Diversity-embedding space-time codes, introduced in S.N. Diggavi et al. (2003), embed a high-diversity code within a high-rate code making opportunistic use of the channel fading conditions. They encode the information symbols into layers each at a prescribed rate-diversity operating point; thus providing an unequal error protection capability. Previous diversity-embedding space-time block codes in S.N. Diggavi et al. (2003) were presented only for 4 transmit antennas. In this paper, we present three new constructions for 2, 3, and 4 transmit antennas by varying the relative transmit power levels between the layers without violating the total transmit power constraint. The relative power scaling factor is optimized (off-line as a function of the constellation size) to achieve a desirable tradeoff between the available coding gains of the transmission layers while controlling the peak to minimum transmit power ratio