Optimal detection considering AGC effects in multiple antenna systems

Most detection methods for multiple input multiple output (MIMO) systems are derived with an assumption that the noise from multiple receive paths is white. However, This assumption cannot be valid according to automatic gain control (AGC) schemes. If the independent AGC scheme which has difference gain for each receive path to minimize the quantization noise is employed, the AGC output noise is not white any more. Therefore, the colored noise effects due to AGC should be considered for the optimal detection. In detail, such colored noise effects should be included in the maximum likelihood (ML) detection criterion and the log likelihood ratio (LLR) calculation.