Improved layered space time architecture over quasi-static fading channels with unequal power allocation and multistage decoding

The Bell labs layered space-time (BLAST) architecture pioneered by Foschini was found to achieve high spectral efficiency with moderate complexity. However, the redundancy in error correcting codes in BLAST receiver is not used in detection improvement, as detection and decoding are carried out separately. In this paper, we investigate a new approach for improved performance of BLAST based on multi-stage decoding (MSD) and unequal transmit power allocation among layers, for transmission over flat quasi-static Rayleigh fading channels. The use of MSD exploits the inherent redundancy in the employed channel codes to improve detection in BLAST without the need for complex iterative decoding approaches. In addition, we investigate unequal transmit power allocation among layers for transmission over flat quasi-static Rayleigh fading channels. We first derive a theorem for power allocation that maximizes outage capacity. We then find the unequal power allocation required to guarantee equal outage capacities among layers in BLAST combined with MSD detection. The proposed power allocation simplifies implementation and improves error performance. Simulation results show that the proposed architecture significantly outperforms existing BLAST schemes in terms of error performance for transmission over flat quasi-static Rayleigh fading channels.