On Fast-Decodable Space-Time Block Codes

In this paper, we focus on full-rate, fast-decodable space-time block codes (STBCs) for 2 x 2 and 4 x 2 multiple-input multiple-output (MIMO) transmission. We first derive conditions for reduced-complexity maximum-likelihood decoding, and apply them to a unified analysis of two families of 2 x 2 STBCs that were recently proposed. In particular, we describe a reduced- complexity sphere decoding algorithm suitable for QAM signal constellations. Next, we derive a novel reduced-complexity 4 x 2 STBC, and show that it outperforms all previously known codes with certain constellations.