ing design problems are stud- ied under a pair of CSI error models. The related contributions and the motivation of our work are summarized as follows. 5.1.1 Related Work and Motivation The prior contributions related to this chapter can be divided into two categories based on the EH model adopted, i.e. the linear [138-173, 178, 180-194, 196-225] and the non-linear EH model [22, 24-121, 123-173, 178, 180-194, 196-198]. In the linear EH model, the power harvested increases linearly with the input power, while the EH under the non-linear model exhibits more realistic non-linear characteristics especially at the power-tail. 5.1.1.1 Linear EH Model In [110], Liu et al. analyzed the performance of a cooperative NOMA system relying on SWIPT, which outperformed OMA. Do et al. [49] extended [110] and studied the beneficial effect of the user selection scheme on the performance of a cooperative NOMA system using SWIPT. In [219], Yang et al. presented a theoretical analysis of two power allocation schemes conceived for a cooperative NOMA system with SWIPT. It was shown that the outage probability achieved under NOMA is lower than that obtained under OMA. Diamantoulakis et al. [41] studied the optimal resource allocation design of wireless- powered NOMA systems. The optimal power and time allocation were designed for maximizing the max-min fairness among users. In their following work [42], a joint downlink and uplink scheme was considered in a wireless powered network, followed by comparisons between NOMA and TDMA. The results show that NOMA is more energy efficient in the downlink of SWIPT networks. In order to improve the EE, multiple antennas were applied in a NOMA system associated with SWIPT, and the transmit beamforming and the power splitting factor were jointly optimized for maximizing the transmit rate of users [216]. The contributions in [110-121, 123-173, 178, 180-194, 196-216] investigated conven- tional wireless NOMA systems, which did not consider the interference between the secondary network and the primary