System and method for employing six-bit rank 1 and 2 codebooks for four transmit antennas

A method for operating a base station, the method comprising:

• taking a channel measurement;
• and
• quantizing the channel measurement using a codebook to produce a selected codeword, the codebook comprising a hierarchical structure consisting of sixteen codeword clusters each of which comprising four codewords, wherein quantizing the channel estimate using a codebook comprises identifying M first level codewords out of the plurality of first level codewords, where M is a non-zero integer value greater than or equal to two, and
• wherein a first codeword in each of the sixteen codeword clusters is a Layer-1 codeword and the remaining three codewords in each of the sixteen codeword clusters are Layer-2 codewords, the Layer-2 codewords not being Layer-1 codewords.

A communications device comprising:

• a processor;
• and
• a computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
• estimate a communications channel between the communications device and a controller serving the communications device to produce a channel estimate;
• and
• quantize the channel estimate using a codebook to produce a selected codeword, wherein the codebook has a hierarchical structure and comprises a plurality of first level codewords and a plurality of sets of subsidiary codewords, wherein the sets of subsidiary codewords do not comprise any first level codewords, and wherein each of the first level codewords is associated with a unique one of the sets of subsidiary codewords, and wherein the instructions to quantize the channel estimate using a codebook include instructions to identify M first level codewords out of the plurality of first level codewords, where M is a non-zero integer value greater than or equal to two.