Patent ID: 8243582

Claim:
A method for feeding back channel state information of downlink (DL) channels from a mobile station (MS) to one or multiple base stations (BSs) in a cell of a wireless IEEE 802.16m network for closed-loop precoding, wherein the DL channels are correlated, comprising: storing an identical codebook at the BS and each MS, wherein the codebook includes a set codewords {V}, such that the codebooks shared between the BSs and the set of MSs; determining, at a particular MS, a covariance matrix on a particular subcarrier j of a particular DL channel as P j =E {( z j +n j )( z j +n j ) H }, where E is expected value operator, H indicates a conjugate transpose, the matrix P j is full-rank, z is inter-cell interference, and n is additive white Gaussian noise (AWGN), and wherein a long term channel covariance matrix is R=P j −1/2 E{H ij H ij H }( P j −1/2 ) H , where H ij is a correlated channel matrix for an i th OFDM symbol and j th subcarrier; quantizing the covariance matrix R; and feeding back the quantized covariance matrix R from the MS to the BS.