Beam Training and Allocation for Multiuser Millimeter Wave Massive MIMO Systems We investigate beam training and allocation for multiuser millimeter wave massive MIMO systems. An orthogonal pilotbased beam training scheme is first developed to reduce the number of training times, where all users can simultaneously perform the beam training with the base station (BS). As the number of users increase, the same beam from the BS may point to different users, leading to beam conflict and multiuser interference. Therefore, a qualityofservice (QoS) constrained (QC) beam allocation scheme is proposed to maximize the equivalent channel gain of the QoSsatisfied users, under the premise that the number of the QoSsatisfied users without beam conflict is maximized. To reduce the overhead of beam training, two partial beam training schemes, an interlaced scanning (IS), and a selection probability (SP)based schemes, are proposed. The overhead of beam training for the ISbased scheme can be reduced by nearly half, while the overhead for the SPbased scheme is flexible. The simulation results show that the QCbased beam allocation scheme can effectively mitigate the interference caused by the beam conflict and significantly improve the spectral efficiency, while the ISbased and SPbased schemes significantly reduce the overhead of beam training at the cost of sacrificing spectral efficiency, a little.

Performance Evaluation of Linear Precoding mmWave MultiUser MIMO Systems with NYUSIM Channel Simulator In this paper, we evaluate the performance of the digital beamsteering (DBS) precoder in multiuser multipleinput multipleoutput (MIMO) systems operating at mmWave frequencies. This evaluation is done using a 3D mmWave statistical channel model developed based on outdoor extensive measurement in New York city. The NYUSIM channel simulator generates 3D realistic statistical temporal and spatial parameters. The DBS performance is evaluated in terms of capacity achieved as a function of the number of users and compared with two classical precoders, namely, zero forcing (ZF) and conjugate beamforming (CB). The base station is equipped with three different antenna array configurations: uniform linear array, uniform square array and uniform rectangular array.Simulation results show that DBS can be realistically considered as an attractive precoder for mmWave multiuser MIMO system with tens of antennas at the base station; tradingoff performance, low implementation complexity and less overhead.