Abstract
Recently, novel full-diversity full-rate quasi-orthogonal space-time block codes (QSTBCs) with power scaling and double-symbol maximum likelihood (ML) decoding was proposed. Specifically, the codes can achieve full-diversity through linearly combining two adequately power scaled orthogonal space-time block codes (OSTBCs). In this letter, we derive expressions for mutual information and post-processing signal-to-noise ratio (SNR) for a system with four transmit antennas. By exploiting these formulas, we propose three transmit antenna grouping (TAG) methods for a closed-loop system with low-rate feedback information. The TAG methods make it possible to provide an excellent error-rate performance even with a low-complexity zero-forcing (ZF) detection, especially in spatially correlated fading channels.
