Channel state information csi reporting method and apparatus

A channel state information CSI reporting method, comprising:

• receiving, by a first communications apparatus, reference signals from a second communications apparatus;
• and
• performing, by the first communications apparatus, channel measurement based on the reference signals, and sending third CSI to the second communications apparatus in a time unit whose identifier is K, wherein the third CSI is used to indicate a channel state in a third reference time unit, wherein
• an identifier of the third reference time unit is K+n3, K is an integer, and n3 is a positive integer.

A channel state information CSI reporting apparatus, comprising:

• a receiving unit, configured to receive reference signals from a second communications apparatus;
• and
• a sending unit, configured to perform channel measurement based on the reference signals, and send first CSI to the second communications apparatus in a time unit whose identifier is m, wherein the first CSI is used to indicate a channel state in a first reference time unit and a channel state in a second reference time unit, wherein
• an identifier of the first reference time unit is m−n1, an identifier of the second reference time unit is m−n1−n2, wherein m, n1, and n2 are integers, and n2 is not equal to 0.