A General Rate Splitting Scheme for Hybrid Precoding in mmWave Systems

To reduce the high hardware cost in millimeter wave (mmWave) systems, hybrid analog/digital precoding structure is employed. Combination of hybrid precoding and massive-element antennas enables mmWave communication to provide a significant throughput gain. However, multiuser interference remains a bottleneck for performance improvement in mmWave systems. In this paper, in order to tackle the multiuser interference, we first introduce a general rate splitting (RS) strategy for mmWave downlink transmission. Then, we analyze the achievable rate regions under joint decoding and successive decoding schemes, respectively. After that, a novel hybrid precoding scheme that aims at maximizing the achievable sum rate under successive decoding is investigated. The proposed algorithm formulates the precoder design problem into a standard semidefinite programming (SDP), which can be solved iteratively with sub-gradient search. Finally, simulation results show that the proposed RS scheme and the hybrid precoding design bring considerable improvements over existing algorithms in rich scattering environments.