Maximum-SNR transmit antenna selection with unimodular beamforming and two receive antennas

The recent increased interest in massive multiple-input multiple-output systems, combined with the cost of the analog RF chains, necessitates the use of efficient antenna selection (AS) schemes. Capacity or SNR optimal AS has been considered to require an exhaustive search among all possible antenna subsets. In this work, we identify in polynomial time a polynomial-size collection of antenna subsets that contains the one that maximizes the post-processing receiver SNR when two receive and an arbitrary number of selected transmit antennas are employed.