)(i) = x(0) (i) where p 0, 4, 5, 7, 8 is the number of the single antenna port used for transmission of the physical channel, =0,1, M'symb - 1, and M'symb May The precoding function for the spatial multiplexing using antenna ports with cell-specific reference signals is only used in conjunction with layer mapping for spatial multiplexing. The spatial multiplexing supports two or four antenna ports and the set of antenna ports used is p = 0,1 or p = 0,1,2,3, respectively. If cyclic delay diversity is not used, then the precoding operation for spatial multiplexing can be expressed as follows: (9-42) where the precoding matrix W(i) is an Np X N1 matrix, i = 0,1, Msymb - 1, Mayme For spatial multiplexing, the precoding matrix W(i) is selected from subsets of the base codebook configured in the eNB and the UE. The eNB may further limit the precoding matrix selection in the UE to a subset of the elements in the base codebook using codebook subset restrictions. For a large-delay CDD scheme, the precoding for spatial multiplexing is defined by: (9-43) (Np-1) where the precoding matrix W(i) is of size Np X N, ,M'symb A(i) is a diagonal N1 X N1 matrix, supporting cyclic delay diversity, and U is a N1 X N1 matrix. The precoding matrix W(i) is selected among the precoder elements in the codebook configured in the eNB and the UE. The eNB can further confine the precoder selection in the UE to a subset of the elements in the codebook using a codebook subset restriction. As an example, for transmission on two antenna ports p = 0,1, the precoding matrix W(i) is selected from Table 9-21 [107]. CHAPTER 9 The IEEE 802. 16m Physical Layer (Part I) Table 9-21 Codebook for Transmission on Antenna Ports p : 0,1[107] Number of Layers N Codebook Index Precoding for transmit diversity is only used in conjunction with layer mapping for transmit diversity. The precoding operation for transmit diversity is defined for two and four antenna ports. For transmission on two antenna ports, p = 0,1, the output y(i) = y(0)(i),y(1)(i)), = 0, 1, 1 of 