Patent ID: 8913683

Claim:
A method of providing channel state information, CSI, for a first communication device communicating with a second communication device over a multiple input multiple output, MIMO, wireless channel using precoding codewords of a precoding codebook, wherein the first and/or second communication devices support communications over the MIMO wireless channel using a plurality of transmission layers, and wherein the precoding codewords of the precoding codebook are divided into transmission layer groups with each transmission layer group of precoding codewords being provided for a respective one of the transmission layers, the method comprising: defining at least a first and a second plurality of precoding codewords of the precoding codebook wherein each of the at least first and second plurality of precoding codewords includes precoding codewords from each of the transmission layer groups; during a first transmission time interval, determining respective performance metrics for the first plurality of precoding codewords of the precoding codebook for the MIMO wireless channel based on transmissions received at the first communications device from the second communication device; and during a second transmission time interval after the first transmission time interval, determining respective performance metrics for the second plurality of precoding codewords of the precoding codebook for the MIMO wireless channel based on transmissions received at the first communication device from the second communication device, wherein the first and second pluralities of precoding codewords are different.