  To realize mmWave massive MIMO systems in practice, Beamspace MIMO with beam
selection provides an attractive solution at a considerably reduced number of
radio frequency (RF) chains. We propose low-complexity beam selection
algorithms based on singular value decomposition (SVD). We first diagonalize
the channel matrix by SVD, and the appropriate beams are selected one-by-one in
a decremental or incremental order based on the criterion of sum-rate
maximization. To reduce the complexity of the proposed algorithms
significantly, we make use of SVD in the last iteration to aviod SVD from
scratch again. Meanwhile, our proposed algorithms naturally obtain the
precoding matrix, which can eliminate the multiusers interference. Simulation
results demonstrate that our proposed algorithms can outperform the competing
algorithms, including the fully digital zero-precoding.
