Methods and apparatus for feeding back channel quality indication in a communication system. First, a first channel quality indication index is determined in dependence upon a channel quality estimation of a first transmission channel, and a second channel quality indication index is determined in dependence upon a channel quality estimation of a second transmission channel. A differential channel quality indication index of the second channel quality indication index is determined with reference to the first channel quality indication index in dependence upon a differential compression scheme. Then, the first channel quality indication index and the differential channel quality indication index are reported.