Patent ID: 8781012

Claim:
A method of transmitting a codebook index in a wireless communication system, the method comprising: receiving a first feedback index from a first receiver, the first feedback index indicating a first vector selected from a plurality of vectors belonging to a feedback codebook; receiving a second feedback index from a second receiver, the second feedback index indicating a second vector selected from the plurality of vectors belonging to the feedback codebook; selecting a precoding matrix from a precoding codebook using the first feedback index and the second feedback index, the precoding codebook comprising a plurality of precoding matrices; transmitting a first interference index informing the precoding matrix to the first receiver; transmitting a second interference index informing the precodig matrix to the second receiver; and transmitting data precoded using the precoding matrix to the first receiver and the second receiver, wherein the first interference index indicates the precoding matrix among a first sub-precoding codebook, the first sub-precoding codebook being a subset of the precoding codebook and including precoding matrices which comprise the first vector, and the second interference index indicates the precoding matrix among a second sub-precoding codebook, the second sub-precoding codebook being a subset of the precoding codebook and including precoding matrices which comprise the second vector.