 subset type for closed-loop MIMO modes Base codebook or 2 and 4 codebook subset Depending on the MIMO feedback mode and the value of Codebook_Subset parameter, the MS feeds back PMI from the SU-MIMO, MU-MIMO base codebook, or from a subset of the SU-MIMO or MU-MIMO base codebook (This parameter is conveyed via the feedback allocation A-MAP IE, or feedback polling A-MAP IE. Codebook feedback mode for closed-loop MIMO Possible selections are as modes 2 and 4 follows: 10.5 IEEE 802.16m downlink MIMO schemes Table 10-26 Downlink MIMO Parameters Continued Type of Information Description of the Parameter Value This parameter specifies the codebook feedback Base mode with mode. If codebook coordination is enabled by setting codebook coordination Codebook_Mode parameter to Ob11 or by setting disabled; Codebook_Coordination parameter to Ob1, and if the Transformation mode with MS reports spatial rate equal to 1, then the MS finds codebook coordination the rate-1 PMI from the codebook entries disabled; broadcasted in BC_SI filed (Rank-1 base codebook Differential mode with subset indication for interference mitigation with PMI codebook coordination coordination) in AAI_DL-IM MAC management disabled; message. Base mode with codebook coordination enabled. The base codebook is a unitary codebook. A codebook is defined as unitary if each of the constituent matrices is unitary. The MS selects its preferred matrix from the base codebook based on the channel measurements and sends the index of the preferred codeword. The BS calculates the precoder matrix W according to the index. Both BS and MS use the same codebook for proper operation. For the base mode, the PMI feedback from a mobile station refers to an entry in the base codebook where the base codebooks are defined for two, four, and eight transmit antennas at the BS. The notation C(N, Ns, NB) denotes the codebook that consists of 2NB complex-valued N X Ns matrices and N5 denotes the number of streams. The notation C(N, Ns, NB,i) denotes the ith codebook entry of C (Nt, Ns,