Multiple-input multiple-output (MIMO) communication system using a codebook and method of designing the codebook

A communication method of a transmitter, the communication method comprising:

• generating a codebook for each eigenvector of a channel matrix or a channel covariance matrix, such that each codebook has a different size based on eigenvalues of the channel matrix or the channel covariance matrix;
• receiving information associated with each of quantized eigenvectors;
• and
• obtaining the quantized eigenvectors using information associated with each of the quantized eigenvectors and the respective codebooks for each eigenvector,
• wherein the generating comprises generating the largest size codebook for a codebook corresponding to a dominant eigenvector from among the eigenvectors,
• wherein each of the eigenvectors is quantized by quantizing an ith eigenvector using the codebook corresponding to the ith eigenvector, projecting the codebook corresponding to an (i+1)th eigenvector onto a null space of the quantized ith eigenvector, and quantizing the (i+1)th eigenvector using the projected codebook corresponding to the (i+1)th eigenvector.

A non-transitory computer-readable storage medium having stored therein program instructions to cause a processor to execute a communication method of a receiver, the communication method comprising:

• calculating an eigenvector matrix comprising eigenvectors of a channel matrix or a channel covariance matrix;
• generating a codebook for each eigenvector of the eigenvector matrix such that each codebook has a different size based on eigenvalues of the channel matrix or the channel covariance matrix;
• quantizing each of the eigenvectors using the respective codebook for each eigenvector;
• and
• transmitting, to a transmitter, information associated with each of the quantized eigenvectors,
• wherein the generating comprises generating a largest size codebook for a codebook corresponding to a dominant eigenvector from among the eigenvectors, wherein the quantizing comprises:
• quantizing an ith eigenvector using the codebook corresponding to the ith eigenvector;
• projecting the codebook corresponding to an (i+1)th eigenvector onto a null space of the quantized ith eigenvector;
• and
• quantizing the (i+1)th eigenvector using the projected codebook corresponding to the (i+1)th eigenvector.

A terminal comprising:

• a codebook generator configured to calculate an eigenvector matrix that comprises a plurality of eigenvectors of a channel matrix or a channel covariance matrix which are based on a channel formed between the terminal and a receiver, configured to generate a codebook for each eigenvector of the eigenvector matrix, and configured to quantize each respective eigenvector;
• and
• a transmitter configured to transmit information about the quantized eigenvectors to the receiver,
• wherein the codebook generator generates at least two codebooks of different size based on eigenvalues of each eigenvector and wherein the codebook generator generates a larger size codebook for dominant eigenvectors and generates a smaller size codebook for non-dominant eigenvectors,
• wherein the codebook generator is further configured to quantize an ith eigenvector using the codebook corresponding to the ith eigenvector, project the codebook corresponding to an (i+1)th eigenvector onto a null space of the quantized ith eigenvector, and quantize the (i+1)th eigenvector using the projected codebook corresponding to the (i+1)th eigenvector.