| CPC H04B 7/0626 (2013.01) [H04B 7/0634 (2013.01)] | 17 Claims |

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1. A method, comprising:
receiving, by a user equipment (UE), at least one channel state information-reference signal (CSI-RS) from a network;
estimating, by the UE, at least one covariance matrix of at least one downlink channel matrix according to the at least one CSI-RS at different times and frequencies;
transmitting, by the UE, at least one parameter associated with the least one covariance matrix to the network; and
compressing, by the UE, the at least one covariance matrix, wherein the at least one covariance matrix is compressed by:
being projected onto at least one two-dimension (2D) time-frequency basis matrix or onto at least one one-dimension (1D) frequency basis vector; or
being represented as at least one linear combination of 2D sinusoids matrix or as at least one linear combination of 1D sinusoids vector.
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