Channel Feedback Codebook Design for Millimeter-Wave Massive MIMO Systems Relying on Lens Antenna Array
IEEE Wireless Communications Letters
The recently proposed millimeter-wave (mmWave) massive MIMO system relying on a lens antenna array (LAA) significantly reduces the number of radio frequency (RF) chains using beam selection. A high data rate can be achieved based on the reduced-dimensional equivalent channel after beam selection. In frequency division duplexing (FDD) systems, the equivalent channel has to be signaled back to the base station (BS) via a feedback channel based on a codebook. However, no dedicated codebook has
... proposed for LAA-aided mm-Wave systems. To fill this gap, in this paper, we propose a reduced-dimensional subspace codebook (RDSC) for LAA-aided mmWave massive MIMO systems. Specifically, under the recently proposed concept of angle coherence time, we first generate the large-dimensional vectors in the channel subspace, which is determined by the angles-of-departure (AoDs) of the dominant paths. Then, based on these vectors in the channel subspace, we create the RDSC by considering both the lens and the beam selector. Finally, the equivalent channel is quantized using the proposed RDSC and fed back to the BS. Finally, we carry out mathematical performance analysis of the proposed RDSC and show that its feedback overhead is rendered proportional to the relatively small number of dominant paths per user. The analytical results are verified by our simulations.