PerformanceImproved UCDBased Hybrid Precoding for MillimeterWave Massive MIMO Single User Systems Hybrid precoding scheme can significantly reduce the number of radio frequency (RF) chains and the huge energy consumption in mmWave massive MIMO systems. Most existing hybrid precoding papers are based on singular value decomposition (SVD) or geometric mean decomposition (GMD). The GMDbased hybrid precoding scheme can avoid the complicated bit allocations in SVDbased method, because it decomposes the channel into several identical SNR subchannels. However, the GMDbased method will suffer from considerable capacity loss at low SNR in mmWave systems. To overcome this shortcoming, we can combine the hybrid precoding structure with uniform channel decomposition (UCD). In this paper, we propose the UCDbased hybrid precoding for mmWave massive MIMO single user systems. Simulation results verify that the proposed UCDbased hybrid precoding scheme outperforms the conventional SVDbased and GMDbased hybrid precoding schemes, because it achieves much higher spectral efficiency and lower bit error rate (BER) at low SNR systems.

Multiuser mmWave MIMO Channel Estimation with Hybrid Beamforming over Frequency Selective Fading Channels In multiuser millimeter wave (mmWave) multiple input multiple output (MIMO) systems, obtaining accurate informationknowledge regarding the channel state is crucial to achieving multiuser interference cancellation and reliable beamforming (BF)xe2x80x93to compensate for severe path loss. This knowledge is nonetheless very challenging to acquire in practice since large antenna arrays experience a low signaltonoise ratio (SNR) before BF. In this paper, a multiuser channel estimation (CE) scheme namely generalizedblock compressed sampling matching pursuit (GBCoSaMP), is proposed for multiuser mmWave MIMO systems over frequency selective fading channels. This scheme exploits the clusterstructured sparsity in the angular and delay domain of mmWave channels determined by the actual spatial frequencies of each path. As the corresponding spatial frequencies of multiuser mmWave MIMO systems with Hybrid BF often fall between the discrete Fourier transform (DFT) bins due to the continuous Angle of Arrival (AoA)Angle of Departure (AoD), the proposed GBCoSaMP algorithm can address the resulting power leakage problem. Simulation results show that the proposed algorithm is effective and offer a better CE performance in terms of MSE when compared to the generalized block orthogonal matching pursuit (GBOMP) algorithm that does not possess a pruning step.