Log-likelihood detection ordering for MMSE-SIC in V-BLAST systems

In the conventional successive interference canceling (SIC) detection algorithm of V-BLAST, the detection ordering does not exploit the instantaneous effect of the noise. In some previous studies, based on zero-forcing SIC (ZF-SIC) scheme, it has been presented that the detection ordering by the magnitude of log-likelihood ratio (LLR) significantly outperforms the conventional detection ordering by signal to noise ratio (SNR) for V-BLAST. In this paper, an extension of LLR-based ordering to the minimum mean square error (MMSE) detector is proposed. We have derived an accurate formula for LLR with respect to MMSE detector. We also propose an approximate formula for LLR, which can decrease the computational complexity in a large extent. The high improvement of system performance is demonstrated via simulation results. Besides, some extensions to M-ary signaling have also been proposed.

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