Limited feedback in massive MIMO systems: Exploiting channel correlations via noncoherent trellis-coded quantization

Accurate channel state information at the transmitter can significantly enhance the performance of multiple antenna systems, but efficient channel quantization techniques must be developed in order to scale such informed transmitter strategies to frequency division duplexed (FDD) massive MIMO systems. Recent results show that noncoherent trellis-coded quantization (NTCQ) is an effective approach for limited feedback transmit beamforming with a large number of transmit antennas. In this paper, we investigate extensions of NTCQ that exploit channel correlations in time and space to significantly reduce the required feedback rate. Our numerical results show that near-optimal beamforming with moderate feedback overhead can be obtained in massive MIMO systems.