Soft-Output MIMO MMSE V-BLAST Detector Under ML Channel Estimation and Channel Correlation

In practical wireless Multiple-Input Multiple-Output (MIMO) communications system, the channel estimation must be imperfect. Unfortunately, the channel estimation errors have not been taken into account by existing soft-output MIMO Minimum Mean Square Error (MMSE) Vertical Bell Lab Space Time (VBLAST) detectors when calculating the Log-Likelihood Ratio (LLR) of each coded bit, i.e., the soft information. As a result, the system performance can be significantly degraded. In this paper, the authors propose a novel soft-output MIMO MMSE V-BLAST detector based on random vector theorem, which takes the estimation error of Maximum Likelihood (ML) MIMO channel estimation and receiver spatially channel correlation into account in the computation of the MMSE filter and LLR of each coded bit.