Method of designing codebook for 3d antenna configuration

A method of determining a codeword in a base station of a communication system with a 3D antenna configuration, the base station being configured with a rectangular antenna array, and the method comprising:

• receiving information about a first index n of a first codeword in a first codebook, information about a second index m of a second codeword in a second codebook and information about a rank r from a user equipment;
• determining a target codeword corresponding to the received first index n, the second index m and the rank r,
• for the rank 1≦r≦NV, the target codeword being represented as:
• Wm,N+n(r)=Tm,nr/∥Tm,nr∥;
• Tm,nr(:,k)=col(Un(r)(:,k)·(Vm(1))T),
• k=1, 2, . . . , r;
• and
• m=0, 1, . . . , 2M−1;
• n=0, 1, . . . , 2N−1;
• for the rank NV<r≦NVNH, the target codeword being represented as:
• WmN+n(r)=Fm,nNV┌r/NV┐(:,1:r)/∥Fm,nNV┌r/NV┐(:,1:r)∥;
• Fm,nNV┌r/NV┐(:,NV(k1−1)+k2)=col(Un(NV)(:,k2)·(Vm(┌r/NV┐)(:,k1))T),
• k1=1, 2, . . . , ┌r/NV┐;
• k2=1, 2, . . . , NV;
• m=0, 1, . . . , 2M−1;
• n=0, 1, . . . , 2N−1
• wherein Um(r) and Vm(r) represent the first codeword and the second codeword with the index m at the rank r respectively, NH represents an amount of the horizontal linear antenna arrays, NV represents an amount of the vertical linear antenna arrays, a size of the horizontal codebook is N bits, a size of the vertical codebook is M bits, col(A) represents a transformation of a matrix A into a column vector, A(:,k) represents the kth column of the matrix A, Tm,nr is a NHNV×r matrix, and Fm,nr is a NHNV×r matrix.