A V-BLAST System Using Modulation Set Selection for Reduced-Complexity Tree Searching in the QRD-M Algorithm

This letter presents a new vertical Bell Labs layered spacetime (V-BLAST) transmission scheme for developing low-complexity tree searching in the QRD-M algorithm. In the new V-BLAST system, we assign modulation scheme in ascending order from top to bottom tree branches. The modulation set to be assigned is decided by two criteria: minimum performance loss and maximum complexity reduction. We also propose an open-loop power allocation algorithm to surmount the performance loss. Numerical results show that the proposed V-BLAST transmission approach can significantly reduce the computational loads of the QRD-M algorithm with a slight performance degradation. key words: vertical Bell Labs layered space-time (V-BLAST), sphere decoding (SD) algorithm, QRD-M algorithm