A novel mode switching scheme utilizing random beamforming for opportunistic energy harvesting

This paper proposes a novel receiver mode switching scheme for simultaneous wireless information and power transfer (SWIPT) and the enabling transmitter design for a point-to-point multiple-input single-output (MISO) channel when the channel state information (CSI) is not available at the transmitter. The proposed scheme employs random beamforming at the transmitter to generate artificial channel fading to enable opportunistic energy harvesting at the receiver when the channel power exceeds a certain threshold. For the proposed scheme, we investigate the achievable average information rate and average harvested energy, as well as trade-offs between them in MISO fading channels. Compared to a reference scheme of periodic receiver mode switching without random transmit beamforming, the proposed scheme is shown to be able to achieve better rate-energy trade-off´s when the harvested energy target is sufficiently large. Particularly, it is revealed that employing one single random beam for the proposed scheme is asymptotically optimal as the transmit power increases to infinity, and also performs the best with finite transmit power for high energy harvesting requirements of practical interests, thus leading to an appealing low-complexity implementation.