Downlink CSI Recovery in Massive MIMO Systems by Proactive Sensing

Accurate channel state information (CSI) is critical to harvest the potential gain brought by massive multiple-input multiple-output (MIMO). However, the acquisition of downlink CSI is challenging in the frequency division duplex (FDD) systems due to limited feedback and the use of low-resolution codebooks. In this letter, we propose a novel sensing-assisted CSI recovery (SACR) scheme, where the BS proactively senses the downlink channel structure so that accurate CSI recovery at the BS can be achieved with only a few number of low-resolution user feedbacks. Numerical results show that the proposed scheme significantly outperforms the existing methods.