Method and apparatus for obtaining channel state information

A method for feeding back channel state information, the method comprising:

• receiving, by user equipment, one or multiple pieces of downlink signaling from a base station, wherein the one or multiple pieces of downlink signaling instruct the user equipment to feed back channel dimension information, wherein the channel dimension information comprises an effective dimension of a channel subspace of a statistical channel between the base station and the user equipment, and the effective dimension of the channel subspace is less than a quantity of reference signal ports used to measure channel state information;
• and
• feeding back, by the user equipment, the channel dimension information to the base station.

An apparatus for obtaining channel state information, the apparatus comprising:

• a transmitter, configured to send one or multiple pieces of downlink signaling to user equipment for instructing the user equipment to feed back channel dimension information, wherein the channel dimension information comprises an effective dimension of a channel subspace of a statistical channel between the apparatus and the user equipment, and the effective dimension of the channel subspace is less than a quantity of reference signal ports used to measure channel state information;
• and
• a receiver, configured to receive the channel dimension information fed back by the user equipment.

An apparatus for feeding back channel state information, the apparatus comprising:

• a receiver, configured to receive one or multiple pieces of downlink signaling from a base station, wherein the one or multiple pieces of downlink signaling instruct the apparatus to feed back channel dimension information, wherein the channel dimension information comprises an effective dimension of a channel subspace of a statistical channel between the base station and the user equipment, and the effective dimension of the channel subspace is less than a quantity of reference signal ports used to measure channel state information;
• and
• a transmitter, configured to feed back the channel dimension information to the base station.