Reporting of channel state information

An apparatus in a mobile station, comprising:

• a storage medium including executable instructions;
• and
• a processor;
• wherein the mobile station communicates with a base station in a multi-carrier cellular communication system having a plurality of sub-carriers, wherein a precoding matrix indicator (PMI) of the plurality of sub-carriers represents a matrix;
• wherein the executable instructions, when executed by the processor, cause the apparatus to
• determine the matrix for the plurality of sub-carriers;
• determine a first sub-index from a plurality of the first sub-indices and a second sub-index for the matrix from a plurality of the second sub-indices;
• and
• report the first sub-index and the second sub-index on a periodic physical uplink control channel (PUCCH);
• wherein the first sub-index and the second sub-index are common for the plurality of sub-carriers, and the PMI comprises the first sub-index and the second sub-index, the plurality of the first sub-indices are a subset of all possible first sub-indices, and the plurality of second sub-indices are a subset of all possible second sub-indices, a quantity of combinations of the plurality of first sub-indices and second sub-indices is smaller than a quantity of possible combinations all possible first sub-indices and second sub-indices.

A non-transitory computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of:

• wherein the executable instructions, when executed by the processor, cause the apparatus to
• determine a matrix for the plurality of sub-carriers in a multi-carrier cellular communication system;
• determine a first sub-index from a plurality of first sub-indices and a second sub-index for the matrix from a plurality of second sub-indices;
• and
• report the first sub-index and the second sub-index on a periodic physical uplink control channel (PUCCH);
• wherein the first sub-index and the second sub-index are common for the plurality of sub-carriers, and the matrix is represented by a precoding matrix indicator (PMI), and the PMI comprises the first sub-index and the second sub-index, the plurality of the first sub-indices are a subset of all possible first sub-indices, and the plurality of second sub-indices are a subset of all possible second sub-indices, a quantity of combinations of the plurality of first sub-indices and second sub-indices is smaller than a quantity of possible combinations all possible first sub-indices and second sub-indices.