Low-complexity hybrid precoding algorithm based on orthogonal beamforming codebook

Millimeter wave (mmWave) communication system provides large unlicensed spectrum which helps to achieve huge capacity leap in the next-generation wireless system. The capacity is further improved by precoding technique in multiple-input-multiple-output (MIMO) transmission systems. Although the adoption of large antenna arrays in mmWave transceivers mitigates the huge path loss, it also increases hardware complexity of traditional digital precoding scheme. Hybrid precoding scheme, where signal is pre-processed in both analog and digital domains, is recently proposed to reduce the hardware cost. In this paper, an orthogonal beamforming codebook for two-dimensional (2D) channel environment is proposed to eliminate the efforts of searching for angle of departure (AoD). Then, by exploiting the orthogonality between beamforming vectors, a low-complexity algorithm of reconstructing hybrid precoder is proposed. Simulation results show that the proposed algorithm requires only 32% of complex multiplications compared with state-of-the-art approach, while suffering from less than 5% of performance loss.