Regularization of covariance matrix and eigenvalue decomposition in a MIMO system

A computer-implemented method for use in a multiple input, multiple output receiver, the computer-implemented method comprising:

• obtaining a noise and interference covariance matrix;
• performing scaling of the noise and interference covariance matrix;
• determining a sum of diagonal elements of the scaled noise and interference covariance matrix;
• performing a first spectral shift by the sum to the scaled noise and interference covariance matrix to obtain a first spectral shifted matrix;
• performing eigenvalue decomposition to the first spectral shifted matrix to obtain an eigenvalue matrix;
• performing a second spectral shift by the sum to the eigenvalue matrix;
• limiting the eigenvalue matrix to a diagonal matrix;
• and
• obtaining a new noise and interference covariance matrix, adding the scaled noise and interference covariance matrix and eigenvalue pairs that are obtained based, at least partly, on the performed eigenvalue decomposition, for use by the receiver to mitigate effects of interference signals and increase throughput.

A non-transitory computer-readable medium comprising instructions for causing an apparatus, wherein the apparatus is for use in a multiple input, multiple output receiver, to perform at least the following:

• obtaining a noise and interference covariance matrix;
• performing scaling of the noise and interference covariance matrix;
• determining a sum of diagonal elements of the scaled noise and interference covariance matrix;
• performing a first spectral shift by the sum to the scaled noise and interference covariance matrix to obtain a first spectral shifted matrix;
• performing eigenvalue decomposition to the first spectral shifted matrix to obtain an eigenvalue matrix;
• performing a second spectral shift by the sum to the eigenvalue matrix;
• limiting the eigenvalue matrix to a diagonal matrix;
• and
• obtaining a new noise and interference covariance matrix, adding the scaled noise and interference covariance matrix and eigenvalue pairs that are obtained based, at least partly, on the performed eigenvalue decomposition, for use by the receiver to mitigate effects of interference signals and increase throughput.