The estimation problem of downlink frequency-selective fading multiple-input multiple-output (MIMO) wireless channels is investigated for the combination of the multicarrier (MC) technique with the vertical Bell Labs layered space-time (V-BLAST) architecture,i.e.,the MC V-BLAST system.One novel shift-invariance coding scheme is firstly proposed for the MC V-BLAST system.By exploiting the induced shift-invariance property,one blind estimation method of downlink frequency-selective fading MIMO wireless channels is further derived.Simulations demonstrate the validity of the shift-invariance coding scheme and the channels blind estimation method.