Outage analysis of cooperative NOMA in 5G systems over Nakagami-m fading channels

The paper studies an energy-constrained cooperative network with non-orthogonal multiple access (NOMA) application under Nakagami-m fading channels. The proposed model ensures the service life of the relay node by equipping with energy harvesting devices. NOMA technique is applied at the multiple users to larger user connections and increase spectral efficiency. Closed-form expression for the outage probability at each user is obtained as well as the two bounds, i.e., the upper hound and the lower hound. By further analyzing the outage probability in the high signal-to-interference-plusnoise ratio (SINR) regime, the appearance of error floor is affirmed by assuming the estimation error. Both analytical and simulation results are provided to demonstrate that the application of NOMA assist the network to yield a significant improvement in spectral efficiency compared with orthogonal multiple access (OMA).