1. A method comprising: quantizing based on a cost function, a change in channel state information in a multiple input multiple output (MIMO) pre-coding system onto at least a first codebook and a second codebook, wherein: each of said first codebook and said second codebook comprises one or more unitary matrices; a dimension of said quantized change in said channel state information is reduced with respect to a dimension of said channel state information; and generating said at least said first code book and said second codebook based on at least said channel state information.