LAUSR

Generalized beamspace modulation (GBM) unleashes a higher multiplexing gain via fewer radio-frequency chains, making it an attractive uplink transmission solution to hybrid mmWave massive multiple-input multiple-output systems. Leaping from its wideband form, namely, wideband GBM (WGBM), a further enhanced version termed precoded WGBM (P-WGBM) will be studied, striving for performance improvement by actively involving the digital precoder. Unfortunately, the seemingly “straightforward” extension proves to be challenging because of the precoding constraint and computation complexity. To overcome these obstacles, this letter has carefully formulated an optimization problem, aiming to find an optimal precoder that retains GBM’s multiplexing merit. By exploiting the beamspace properties, we arrive at an efficient technique to achieve near-optimal precoding. Whist keeping all major advantages of WGBM, simulations show that P-WGBM can achieve a remarkable coding gain over WGBM at a small complexity cost.