Low Complexity Adaptive Design for Full-Diversity Full-Rate Space-Time Codes

Full-diversity full-rate (FDFR) space-time codes for open-loop multiple antenna systems achieve both high data rate and good performance but come with very high decoding complexity. In this paper, we propose a low-complexity adaptive FDFR design for closed-loop multiple-input multiple-output systems. With only partial channel subspace knowledge at the transmitter, we adapt the open-loop FDFR code to the channel to maintain the special layer structure of the code at the receiver. That special layer structure enables us to decouple the joint detection over dimension C^Nt2 into N_t individual decoders of dimension C^Nt, where N_t is the number of transmit antennas. This can also be seen as combining the channel diagonalization with signal diversity rotation. The performance of the proposed scheme is analyzed, and it is shown that the full diversity property is maintained in the adaptive design. Adaptive power loading is also incorporated to further exploit channel state information in term of the knowledge of the singular values of the channel. The optimal loading schemes are derived for systems with linear receivers