Section: 6.3.4.2.3 Codebook for precoding and CSI reporting
Content: For transmission on two antenna ports, , and for the purpose of CSI reporting based on two antenna ports or , the precoding matrix shall be selected from Table 6.3.4.2.3-1 or a subset thereof. For the closed-loop spatial multiplexing transmission mode defined in TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4], the codebook index 0 is not used when the number of layers is . Table 6.3.4.2.3-1: Codebook for transmission on antenna ports and for CSI reporting based on antenna ports or For transmission on four antenna ports, , the precoding matrix shall be selected from Table 6.3.4.2.3-2 or a subset thereof. For the purpose of CSI reporting based on four antenna ports or , the precoding matrix shall be selected from Table 6.3.4.2.3-2 or a subset thereof except for alternativeCodeBookEnabledFor4TX-r12 =TRUE in which case the precoding matrix shall be selected from Tables 7.2.4-0A, 7.2.4-0B, 7.2.4-0C, 7.2.4-0D in [4] or a subset thereof, and except for advancedCodebookEnabled = TRUE in which case the precoding matrix shall be selected from Table 7.2.4-17C in [4] or a subset thereof. The quantity denotes the matrix defined by the columns given by the set from the expression where is the identity matrix and the vector is given by Table 6.3.4.2.3-2. Table 6.3.4.2.3-2: Codebook for transmission on antenna ports and for CSI reporting based on antenna ports or For the purpose of CSI reporting for 8, 12, 16, 20, 24, 28, and 32 CSI reference signals the codebooks are given in clause 7.2.4 of TS 36.213[ Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ]  [4].