1. A method of determining indices for matrix codewords in a matrix codeword codebook, the matrix codewords adapted for communicating information between a transmitter and a receiver, the method comprising: retrieving from temporary storage an eigenmode representation for a communications channel, wherein the representation of the eigenmode is based upon on a received signal precoded by a first matrix codeword; performing a test on multiple vector codewords to identify a first vector codeword among the multiple vector codewords, wherein the test includes determining a relationship between the first vector codeword and the eigenmode representation, the first vector codeword is associated with a first vector codeword index that identifies the first vector codeword; and generating a matrix codeword index associated with a second matrix codeword in the matrix codeword codebook, wherein the matrix codeword index is based upon the first vector codeword index, and the order of the first vector codeword is different from the order of the second matrix codeword.