Before revision:  With the growing complexity of CSI  in massive MIMO system , traditional compressive sensing based CSI feedback has become a bottleneck problem that is limited in piratical . Recently, numerous deep learning based CSI feedback approaches demonstrate the efficiency and potential.
After revision:  With the growing complexity of CSI in massive MIMO system , traditional compressive sensing based CSI feedback approaches have limited performance . Recently, numerous deep learning based CSI feedback approaches demonstrate the efficiency and potential.