Optimal Detection Ordering for V-BLAST

In this paper, we propose an optimal metric for detection ordering in terms of symbol error rate (SER) in vertical Bell-lab Layered Space-Time (V-BLAST) systems. Motivated by the log-likelihood ratio based ordering scheme introduced in [1], a new ordering method is presented which can further enhance the V-BLAST performance. The proposed ordering based on the new metric minimizes the SER by exploiting the instantaneous noise and considering its correlation at the linear filter output. A simpler suboptimal ordering metric is also proposed which requires much less computational complexity than that of the optimal ordering metric. We further show that there exists a simplified version of the suboptimal ordering metric for BPSK and 4QAM which achieves a significant performance gain over the conventional ordering scheme with no additional complexity. Simulation results show that the optimal ordering scheme achieves a performance gain of 13 dB at a SER of 10 over conventional signal-to-noise ratio (SNR) ordering schemes with four transmit and four receive antennas. The performance of the suboptimal ordering scheme is shown to be less than 2 dB away from that of the optimal ordering.