Channel state information feedback method, terminal device, and network device

Abstract

Embodiments of the present invention provide a channel state information feedback method, a terminal device, and a network device. The method includes: sending, by a terminal device, matrix information of a dimension reduction matrix to a network device, where a first dimension of the dimension reduction matrix is the same as a quantity of transmit antenna ports of the network device, and a second dimension of the dimension reduction matrix is less than the first dimension of the dimension reduction matrix; and sending, by the terminal device, vector information of an eigenvector of a downlink equivalent channel to the network device, where the eigenvector of the downlink equivalent channel is obtained based on the dimension reduction matrix.

1 . A channel state information feedback method carried out by a network device, wherein the method comprises:
 sending a downlink reference signal based on a dimension reduction matrix, wherein a first dimension of the dimension reduction matrix is the same as a quantity of transmit antenna ports of the network device, and a second dimension of the dimension reduction matrix is less than the first dimension of the dimension reduction matrix;   receiving a vector information of an eigenvector of a downlink equivalent channel of the downlink reference signal from a terminal device;   determining a precoding matrix based on the dimension reduction matrix and the vector information.   
     
     
         2 . The method according to  claim 1 , wherein the method comprises:
 determining the dimension reduction matrix based on channel matrices corresponding to uplink reference signals received in the first time period.   
     
     
         3 . The method according to  claim 2 , wherein the determining the dimension reduction matrix based on channel matrices corresponding to uplink reference signals received in a first time period comprises:
 calculating a first covariance matrix based on the channel matrices corresponding to the uplink reference signals received in the first time period, where the first covariance matrix is used to represent a statistical feature that is of the uplink channel and that is corresponding to the first time period; and   calculating the dimension reduction matrix based on the first covariance matrix.   
     
     
         4 . The method according to  claim 3 , wherein the calculating a first covariance matrix based on the channel matrices corresponding to the uplink reference signals received in the first time period comprises:
 calculating a covariance matrix of each of the channel matrices corresponding to the uplink reference signals received in the first time period;   averaging covariance matrices corresponding to uplink reference signals received at a same moment, to obtain a plurality of second covariance matrices, where the plurality of second covariance matrices are in a one-to-one correspondence with a plurality of moments included in the first time period; and   performing averaging or time-domain filtering on the plurality of second covariance matrices to obtain the first covariance matrix.   
     
     
         5 . The method according to  claim 1 , wherein, during the receiving, the vector information is received over an uplink data channel. 
     
     
         6 . The method according to  claim 1 , wherein the vector information comprises an index of the eigenvector, or an information obtained by quantizing an element of the eigenvector. 
     
     
         7 . The method according to  claim 1 , wherein all columns of the dimension reduction matrix correspond to a same beam directivity pattern. 
     
     
         8 . The method according to  claim 1 , wherein a period in which the network device determines the dimension reduction matrix is longer than a period in which the network device receives the vector information. 
     
     
         9 . A network device, comprising:
 a processor; and   a non-transitory computer-readable storage medium coupled to the processor and storing programming instructions for execution by the processor, the programming instructions instruct the processor to carry out a method comprising:   sending a downlink reference signal based on a dimension reduction matrix, wherein a first dimension of the dimension reduction matrix is the same as a quantity of transmit antenna ports of the network device, and a second dimension of the dimension reduction matrix is less than the first dimension of the dimension reduction matrix;   receiving a vector information of an eigenvector of a downlink equivalent channel of the downlink reference signal from a terminal device; and   determining a precoding matrix based on the dimension reduction matrix and the vector information.   
     
     
         10 . The network device according to  claim 9 , wherein the to method further comprises:
 determining the dimension reduction matrix based on channel matrices corresponding to uplink reference signals received in the first time period.   
     
     
         11 . The network device according to  claim 10 , wherein the programming instructions specifically instruct the processor to perform the operations of:
 calculating a first covariance matrix based on the channel matrices corresponding to the uplink reference signals received in the first time period, where the first covariance matrix represents a statistical feature that is of the uplink channel and that corresponds to the first time period; and   calculating the dimension reduction matrix based on the first covariance matrix.   
     
     
         12 . The network device according to  claim 11 , wherein the programming instructions specifically instruct the processor to perform the operations of:
 calculating a covariance matrix of each of the channel matrices corresponding to the uplink reference signals received in the first time period;   averaging covariance matrices, corresponding to uplink reference signals received at a same moment, to obtain a plurality of second covariance matrices, where the plurality of second covariance matrices are in a one-to-one correspondence with a plurality of moments included in the first time period; and   performing an averaging operation or time-domain filtering operation on the plurality of second covariance matrices to obtain the first covariance matrix.   
     
     
         13 . The network device according to  claim 9 , wherein during the receiving the network device receives the vector information over an uplink data channel. 
     
     
         14 . The network device according to  claim 12 , wherein the vector information comprises an index of the eigenvector or an information obtained by quantizing an element of the eigenvector. 
     
     
         15 . The network device according to  claim 9 , wherein all columns of the dimension reduction matrix correspond to a same beam directivity pattern. 
     
     
         16 . The network device according to  claim 9 , wherein a period in which the network device determines the dimension reduction matrix is longer than a period in which the network device receives the vector information. 
     
     
         17 . A terminal device, comprising:
 a processor; and   a non-transitory computer-readable storage medium coupled to the processor and storing programming instructions for execution by the processor, the programming instructions instruct the processor to carry out a method comprising:   receiving a downlink reference signal from a network device;   obtaining a dimension reduction matrix based on the downlink reference signal, wherein a first dimension of the dimension reduction matrix is the same as a quantity of transmit antenna ports of the network device, and a second dimension of the dimension reduction matrix is less than the first dimension of the dimension reduction matrix; and   sending vector information of an eigenvector of a downlink equivalent channel according to the dimension reduction matrix to the network device.   
     
     
         18 . The terminal device according to  claim 17 , wherein the vector information comprises an index of the eigenvector or an information obtained by quantizing an element of the eigenvector. 
     
     
         19 . The terminal device according to  claim 17 , wherein all columns of the dimension reduction matrix are corresponding correspond to a same beam directivity pattern.