Improving Energy Efficiency in Massive MIMO: Joint Digital Beam-steering and TR-PAPR Reduction

CHRISTIAN A. SCHMIDT; M. CRUSSIÈRE; J. F. HELARD; TONELLO, ANDREA M.

IET COMMUNICATIONS

INST ENGINEERING TECHNOLOGY-IET

Año: 2020

1751-8628

In this article, we propose a novel architecture based on the combination of peak-to-average power ratio (PAPR) reduction with digital beamforming (BF) for mm-wave massive multiple-input multiple-output (MIMO) systems. In order to keep the power amplifiers (PAs) working at the same input back-off (IBO) thus maximizing the system power efficiency, we propose to perform time-domain transmit beam-steering by adding progressive time delays to the signals at each antenna element, while keeping the amplitude weights unitary. We show that these time delays can be obtained with an FIR filter implementation of time-domain fractional delay filter (TD-FDF) structures such as Lagrange interpolation polynomials. We also introduce an analysis on the PAPR of the interpolated signals, where we derive an upper bound to it and show that its value is similar to that of the signal at the input of the interpolation filters, showing the feasibility of the proposed method. In addition, we present a detailed analysis where we show that a significant reduction in computational complexity is obtained when compared to frequency-domain BF. Simulation results validate that the novel proposed scheme combining PAPR reduction and digital BF offers high-precision beam-steering while maintaining reduced PAPR in the delayed signals fed to the antennas.