Hardware-Efficient Hybrid Precoding for Millimeter Wave Systems With Multi-Feed Reflectarrays

Current hybrid precoding schemes for large-scale antenna array-aided millimeter wave (mmWave) wireless systems adopt either full-connected or sub-connected architectures based on phased array antennas (PAAs). The former achieves excellent precoding performance but imposes considerably high hardware complexity, while the latter is relatively simple but suffers from high performance loss. In this paper, we exploit the new technology of reflectarray antennas, which among other advantages offers significant hardware efficiency gain, and propose a novel hybrid precoding architecture based on multi-feed reflectarray antennas (MRAs) for mmWave wireless systems, which is capable of achieving considerable hardware efficiency gain even over the low-hardware-complexity sub-connected architecture with PAAs. The mathematical model is provided for this novel hybrid precoding architecture, and an efficient alternating descent algorithm is developed to jointly design the analog and digital precoders for the proposed hybrid precoding scheme. Numerical results obtained demonstrate that our proposed precoding scheme with MRAs achieves much better precoding performance than its sub-connected counterpart with PAAs.