In a wireless communications system, a transmit end and a receive end use multiple antennas in a spatial multiplexing manner to acquire a higher rate. Compared with a general spatial multiplexing method, an enhanced technology is that a receive end feeds back channel information to a transmit end, and the transmit end uses some transmission precoding technologies according to the obtained channel information, which greatly improves transmission performance.
To obtain higher cell average spectral efficiency and improve cell-edge coverage and throughput, based on an existing Long Term Evolution (LTE for short) system, Long Term Evolution-Advanced (LTE-A for short) supports a maximum of eight antennas in the downlink, and some feedback enhancement technologies are put forward in terms of codebook feedback, which are mainly to enhance codebook feedback precision, and reduce overheads by using a time correlation and/or a frequency-domain correlation of channel information. For one sub-band or multiple joint sub-bands that need to feed back channel information, user equipment measures channel state information (CSI for short) according to a channel state information-reference signal (CSI-RS for short), and feeds back, to a base station, information about two precoding matrix indicators (PMI for short): a PMI1 and a PMI2, where the PMI1 is corresponding to a codeword W1 in a codebook C1, and the PMI2 is corresponding to a codeword W2 in another codebook C2. The base station end has information about the same C1 and C2, and finds the corresponding codewords W1 and W2 from the corresponding codebooks C1 and C2 after receiving the PMI1 and the PMI2, to obtain a codebook corresponding to a virtual W.
However, as an antenna scale increases, pilot overheads used to measure a precoding matrix, that is, overheads of the foregoing CSI-RS, also increase in the prior art.