Constructive Interference Optimization for Hybrid Beamforming with Data-aided Symbol-level Precoding in Multi-user MISO System

The data-aided symbol-level precoding scheme has been known as a useful means of improving the system efficiency in multi-user multi-input single-output (MISO) system, especially with a full digital beamforming. As the number of antenna elements increases, it must be extended to hybrid beamforming with a limited number of radio frequency (RF) chains, while degrading its performance. In this paper, we provide a solution approach to the minimum mean-square estimation (MMSE)-based constructive interference optimization (CIO) problem for hybrid beamforming. As it has to resort to the local optimal solution with hybrid beamforming with a limited number of RF chains, its performance turns out to be much worse than that of full digital beamforming. However, its capacity has been shown to exceed that of the existing scheme, indicating that the data-aided symbol-level precoding would be still useful for a massive number of antenna elements in practice.