Method and apparatus for antenna array channel feedback

An apparatus comprising:

• a receiver configured to receive a set of channel state information reference signals;
• a controller configured to determine a precoding matrix based on the received set of channel state information reference signals, where the precoding matrix has a representation in terms of three components,
• where the first component of the three components is determined from a first set of vectors,
• where the second component of the three components is determined from a first set of parameters, and
• where the third component of the three components is determined from a second set of parameters, where the second set of parameters is a set of unit-magnitude scalars;
• and
• a transmitter configured to transmit a representation of at least one of the first component, the second component, and the third component.

A method comprising:

• receiving, at a wireless terminal, a set of channel state information reference signals,
• where each channel state information reference signal of the set of channel state information reference signals is associated with a corresponding channel state information reference signal antenna port,
• where each channel state information reference signal antenna port is representative of one or more vertically aligned antenna elements of a multi-column antenna array at a base station, and
• where each column in the multi-column antenna array comprises a plurality of antenna elements;
• determining, by the wireless terminal, a precoding matrix based on the received set of channel state information reference signals,
• where the precoding matrix has a representation in terms of three components,
• where the first component of the three components is determined from a first set of vectors,
• where the second component of the three components is determined from a first set of parameters, and
• where the third component of the three components is determined from a second set of parameters, where the second set of parameters is a set of unit-magnitude scalars, and
• where the precoding matrix is at least represented as a product of three component matrices,
• where the first component matrix of the three component matrices is determined from the first component,
• where the second component matrix of the three component matrices is determined from the second component, and
• where the third component matrix of the three component matrices is determined from the third component;
• and
• transmitting, by the wireless terminal, a representation of at least one of the first component, the second component, and the third component.