Widely Linear Multiuser Simultaneous Information and Power Transfer with One-Dimensional Signaling

Emerging wireless technologies require the support for a massive number of low data rate battery operated devices. With this motivation, this paper employs widely linear processing in simultaneous wireless information and power transfer (SWIPT) systems. By considering the transmission of low-rate one-dimensionally modulated signals in the downlink of a SWIPT broadcast channel, a widely linear zero forcing (ZF) precoder and a widely linear minimum mean square error (MMSE) precoder are proposed which are capable of offering service to more users than the number of transmit antennas. Semi closed-form solutions are obtained for both scenarios and iterative dual ascent based algorithms are presented to obtain the transmit precoding (beamforming) matrices. Simulation results demonstrate the effect of widely linear processing in increasing the number of information decoding devices.