Beamforming and Power Splitting in Cooperative 5G systems based on SWIPT, NOMA, and Sun Energy Harvesting

In 5G wireless communication networks, the non-orthogonal multiple access (NOMA) and the simultaneous wireless information and power transfer (SWIPT) methods can be exploited to improve the spectral efficiency and link reliability, respectively. This paper focuses on a cooperative SWIPT NOMA protocol in MISO downlink case, where a user with strong channel conditions, i.e. user 2 (U2), acts as an energy harvesting (EH) relay to assist a user with poor channel conditions, i.e. user 1 (U1). Furthermore, U2 exploits sun energy harvesting, along with the RF signal energy harvesting through SWIPT, to improve the system performance. A jointly optimizing design is performed on the power splitting (PS) ratio of the relay and beamforming vector of the transmitter to maximize the data rate of U2 subject to satisfying the QoS requirement of U1. We have formulated the optimization problem and evaluated the system performance for different values of harvested sun powers. Our results show that exploiting the solar energy harvesting provides a considerable improvement for the cooperative SWIPT NOMA method in terms of system sum rate and feasible probability of the optimization, especially at low SNR regimes.