Channel state information feedback method in reconfigurable intelligent surface-based massive MIMO system

A downlink channel state information feedback method between a transmitter and a receiver, wherein downlink channel state information is acquired in the receiver and fed back to the transmitter in a reconfigurable intelligent surface (RIS)-based multi-user (MU)-multi-input multi-output (MIMO) system, the downlink channel state information feedback method comprising:

• a downlink channel state information acquisition step for acquiring the downlink channel state information via the RIS from a reception signal;
• an angle domain transform step for transforming the acquired downlink channel state information into a channel state information matrix in an angle domain;
• a codeword index derivation step for compressing the channel state information matrix transformed in the angle domain transform step, and deriving a codeword index corresponding to a corresponding vector from a compressed downlink channel state information vector;
• a channel state information vector estimation step for receiving a feedback of the derived codeword index to estimate a measurement vector, and estimating a sparse vector using the estimated measurement vector to estimate the compressed downlink channel state information vector;
• and
• a step for recovering a downlink channel state information matrix using the estimated compressed downlink channel state information vector.