1. A method implemented in a multi-rank beamforming wireless communications system, comprising: precoding a signal in accordance with a codebook comprising a plurality of codebook entries per rank; and transmitting the precoded signal, wherein the codebook restricts elements of codebook entries to be within a predetermined finite set of complex numbers, and each entry in the codebook has both equal column norm and equal row norm, and wherein the wireless communications system has at least 4 transmission antennas.