Method and apparatus for obtaining precoding matrix indicator

An apparatus for obtaining a precoding matrix indicator, comprising:

• a first rotation matrix obtaining module, configured to obtain a first rotation matrix according to first channel information;
• a first differential matrix obtaining module, configured to obtain a first differential matrix according to the first rotation matrix and an instantaneous beam forming matrix/precoding matrix that is obtained currently after the first rotation matrix obtaining module obtains the first rotation matrix;
• and
• a differential precoding matrix indicator obtaining module, configured to quantize, according to a first differential codebook, a pre-acquired first rank indicator, and preset quantization criteria, the first differential matrix to obtain a differential precoding matrix indicator after the first differential matrix obtaining module obtains the differential matrix;
• wherein the first channel information is one of a first long-term channel covariance matrix and a reference precoding matrix indicator;
• and
• when the first channel information is the first long-term channel covariance matrix, the first rotation matrix obtaining module comprises:
• an eigen matrix obtaining unit, configured to perform eigenvalue decomposition on the first long-term channel covariance matrix to obtain an eigen matrix of the first long-term channel covariance matrix, wherein the first long-term channel covariance matrix is obtained by averaging multiple channel matrixes obtained locally on a single or multiple subcarriers in a preset time period;
• and a first rotation matrix obtaining unit, configured to use the eigen matrix of the first long-term channel covariance matrix as the first rotation matrix after the eigen matrix obtaining unit obtains the eigen matrix;
• or
• when the first channel information is the reference precoding matrix indicator, the first rotation matrix obtaining module comprises:
• a second rotation matrix obtaining unit, configured to normalize respective columns of a precoding matrix and use a normalized precoding matrix as the first rotation matrix if the reference precoding matrix indicator is orthogonal to columns of the precoding matrix corresponding to the pre-acquired first rank indicator and the rank is full;
• and a third rotation matrix obtaining unit, configured to:
• select a full-rank precoding matrix corresponding to the reference precoding matrix indicator, normalize respective columns of the full-rank precoding matrix, and use a normalized full-rank precoding matrix as the first rotation matrix if the reference precoding matrix indicator is orthogonal to columns of a precoding matrix corresponding to the pre-acquired first rank indicator and the rank is not full, but a codebook corresponding to the reference precoding matrix indicator meets nesting characteristics;
• or, if the first channel information is the reference precoding matrix indicator, the first rotation matrix obtaining module comprises:
• a fourth rotation matrix obtaining unit, configured to normalize respective columns of precoding matrixes corresponding to the reference precoding matrix indicator and the pre-acquired first rank indicator;
• and perform QR decomposition for a normalized precoding matrix to obtain the first rotation matrix.

A data sending apparatus, comprising:

• a rotation matrix obtaining module, configured to obtain a second rotation matrix according to second channel information;
• a differential matrix obtaining module, configured to:
• obtain a differential matrix according to a received differential precoding matrix indicator and by using a differential codebook and a pre-acquired second rank indicator, wherein the differential precoding matrix indicator is obtained by a data receiving apparatus according to a first rotation matrix and an instantaneous beam forming matrix/precoding matrix, which are obtained by the data receiving apparatus, and by using a first differential codebook and a pre-acquired first rank indicator, the first rotation matrix is obtained according to a first channel information, the second channel information is the same as the first channel information, and the second differential codebook and the second rank indicator are the same as the first differential codebook and the first rank indicator respectively;
• and
• a precoding matrix reconstructing module, configured to reconstruct the beam forming matrix/precoding matrix according to the second rotation matrix obtained by the rotation matrix obtaining module and the differential matrix obtained by the differential matrix obtaining module.