Attention Mechanism Based Intelligent Channel Feedback for mmWave Massive MIMO Systems

The potential advantages of intelligent wireless communications with millimeter wave (mmWave) and massive multiple-input multiple-output (MIMO) are all based on the availability of instantaneous channel state information (CSI) at the base station (BS). However, in frequency division duplex (FDD) systems, no existence of channel reciprocity leads to the difficult acquisition of accurate CSI at the BS. In recent years, many researchers explored effective architectures based on deep learning (DL) to solve this problem and proved the success of DL-based solutions. However, existing schemes focused on the acquisition of complete CSI while ignoring the beamforming and precoding operations. In this paper, we propose an intelligent channel feedback architecture designed for beamforming based on attention mechanism and eigen features. That is, we design an eigenmatrix and eigenvector feedback neural network, called EMEVNet. The key idea of EMEVNet is to extract and feedback effective information meeting the requirements of beamforming and precoding operations at the BS. With the help of the attention mechanism, the proposed EMEVNet can be considered as a dual channel auto-encoder, which is able to jointly encode the eigenmatrix and eigenvector into codewords. Hence, the EMEVNet consists of an encoder deployed at the user and the decoder at the BS. Each user first utilizes singular value decomposition (SVD) transformation to extract the eigen features from CSI, and then selects an appropriate encoder for a specific channel to generate feedback codewords.