“…We then apply a rotation for each codeword to obtain the rotated codebook for each generated orthogonal vectors by Then, the rotated codebook for each rotation vector is constructed by . With a specific codebook design, the quantisation error is reduced since only the local region is quantised instead of the whole region [7]. - Step 4: By using the rotated codebook designed in step 3 , the CDI of each cluster in the set of obtained step 2 is quantised according to the following rule:
Then, the corresponding indexes of the quantised CSI, , are fed back to the Alice through the limited feedback link.…”