Codebook searching apparatus and method thereof

A codebook searching method for a communication system, wherein the communication system uses a codebook having L pre-coding matrices, and L is greater than or equal to 2, the codebook searching method comprising:

• calculating L matrices according to the L pre-coding matrices, wherein and the L matrices are inversed MSE matrices of the L pre-coding matrices;
• and
• selectively executing one of a first to a fourth steps when the L pre-coding matrices are non-square,
• wherein the first step comprises:
• calculating determinants of the L matrices;
• calculating cofactors of diagonals of the L matrices;
• finding a maximum cofactor of the diagonal of each of the L matrices;
• and
• finding a pre-coding matrix corresponding to a minimum one of ratios between the maximum cofactors of the diagonals and the determinants of the L matrices;
• wherein the second step comprises:
• calculating the determinants of the L matrices;
• and
• obtaining a pre-coding matrix corresponding to the maximum one of the determinants of the L matrices;
• wherein the third step comprises:
• calculating diagonal products of the L matrices;
• eliminating (L−S) matrices with relatively small diagonal products from the L matrices to remain S matrices, wherein S is less than L and is greater than or equal to 1;
• calculating determinants of the S matrices;
• calculating cofactors of diagonals of the S matrices;
• finding a maximum cofactor of the diagonal of each of the S matrices;
• and
• finding a pre-coding matrix corresponding to a minimum one of ratios between the maximum cofactors of the diagonals and the determinants of the S matrices;
• wherein the fourth step comprises:
• calculating the diagonal products of the L matrices;
• eliminating (L−S) matrices with relatively small diagonal products from the L matrices to remain S matrices, wherein S is less than L and is greater than or equal to 1;
• calculating the determinants of the S matrices;
• and
• finding a pre-coding matrix corresponding to a maximum one of the determinants of the S matrices.

A codebook searching apparatus for a communication system, wherein the communication system uses a codebook having L pre-coding matrices, and L is greater than or equal to 2, the codebook searching apparatus comprising:

• a matrix operation unit, calculating L matrices according to the L pre-coding matrices, wherein the L matrices are inversed MSE matrices of the L pre-coding matrices;
• a judgment unit, judging whether the L pre-coding matrices are square, and controlling a calculation unit and a decision unit;
• the calculation unit, calculating maximum cofactors of diagonals of the L matrices when the L pre-coding matrices are square, and calculating the maximum cofactors of the diagonals and determinants of at least S matrices of the L matrices when the L pre-coding matrices are non-square, wherein L is greater than S;
• and
• the decision unit, finding a pre-coding matrix corresponding to a minimum one of the maximum cofactors of the diagonals of the L matrices when the L pre-coding matrices are square, and finding a pre-coding matrix corresponding to a minimum one of ratios between the maximum cofactors of the diagonals and the determinants of the at least S matrices when the L pre-coding matrices are non-square.

A codebook searching apparatus for a communication system, wherein the communication system uses a codebook having L pre-coding matrices, and L is greater than or equal to 2, the codebook searching apparatus comprising:

• a matrix operation unit, calculating L matrices according to the L pre-coding matrices, wherein the L matrices are inversed MSE matrices of the L pre-coding matrices;
• a judgment unit, judging whether the L pre-coding matrices are square, and controlling a calculation unit and a decision unit;
• the calculation unit, calculating maximum cofactors of diagonals of the L matrices when the L pre-coding matrices are square, and calculating determinants of at least S matrices of the L matrices when the L pre-coding matrices are non-square, wherein L is greater than S;
• and
• the decision unit, finding a pre-coding matrix corresponding to a minimum one of the maximum cofactors of the diagonals of the L matrices when the L pre-coding matrices are square, and finding a pre-coding matrix corresponding to a maximum one of the determinants of the at least S matrices when the L pre-coding matrices are non-square.