Beam-Domain SWIPT for mMIMO System With Nonlinear Energy Harvesting Legitimate Terminals and a Non-Cooperative Terminal

Abstract

In this paper, we design the simultaneous wireless information and power transfer (SWIPT) protocol for massive multi-input multi-output (mMIMO) system in the beam-domain (BD). In this system, the base station (BS) serves a set of fixed uplink half-duplex legitimate terminals with nonlinear energy harvester. Meanwhile, a non-cooperative energy harvesting (EH) terminal, which is not pay for the energy transmission or untrusted, is also within the coverage of the BS. Considering the nonlinearity of practical EH circuits, we adopt the realistic nonlinear EH model rather than the idealistic linear EH model. The entire protocol can be divided into two phases. The first phase is designed for legitimate terminals EH and downlink training. A BD energy beamformer is employed for wireless energy transmission. Meanwhile, the received energy of the non-cooperative EH terminal is minimized. In the second phase, the BS forms the two-layer receive beamformers for the reception of signals transmitted by legitimate terminals. In order to improve the spectral efficiency (SE) and energy efficiency (EE) of the system, the BS transmit power and time switching ratio are optimized. Simulation results show the superiority of the proposed BD SWIPT protocol on SE and EE compared with the conventional mMIMO SWIPT protocols.