  This paper proposes a new transmission strategy for the multiuser massive
multiple-input multiple-output (MIMO) systems, including uplink/downlink
channel estimation and user scheduling for data transmission. A discrete
Fourier transform (DFT) aided spatial basis expansion model (SBEM) is first
introduced to represent the uplink/downlink channels with much few parameter
dimensions by exploiting angle reciprocity and the physical characteristics of
the uniform linear array (ULA). With SBEM, both uplink and downlink channel
estimation of multiuser can be carried out with very few amount of training
resources, which significantly reduces the training overhead and feedback cost.
Meanwhile, the pilot contamination problem in the uplink raining is immediately
relieved by exploiting the spatial information of users. To enhance the
spectral efficiency and to fully utilize the spatial resources, we also design
a greedy user scheduling scheme during the data transmission period. Compared
to existing low-rank models, the newly proposed SBEM offers an alternative for
channel acquisition without need of channel statistics for both TDD and FDD
systems based on the angle reciprocity. Moreover, the proposed method can be
efficiently deployed by the fast Fourier transform (FFT). Various numerical
results are provided to corroborate the proposed studies.
