  By employing the lens antenna array, beamspace MIMO can utilize beam
selection to reduce the number of required RF chains in mmWave massive MIMO
systems without obvious performance loss. However, to achieve the
capacityapproaching performance, beam selection requires the accurate
information of beamspace channel of large size, which is challenging,
especially when the number of RF chains is limited. To solve this problem, in
this paper we propose a reliable support detection (SD)-based channel
estimation scheme. Specifically, we propose to decompose the total beamspace
channel estimation problem into a series of sub-problems, each of which only
considers one sparse channel component. For each channel component, we first
reliably detect its support by utilizing the structural characteristics of
mmWave beamspace channel. Then, the influence of this channel component is
removed from the total beamspace channel estimation problem. After the supports
of all channel components have been detected, the nonzero elements of the
sparse beamspace channel can be estimated with low pilot overhead. Simulation
results show that the proposed SD-based channel estimation outperforms
conventional schemes and enjoys satisfying accuracy, even in the low SNR
region.
