Performance analysis of cooperative NOMA with energy harvesting in multi-cell networks

In this paper, an energy harvesting enabled cooperative non-orthogonal multiple access (NOMA) system for a multi-cell network is investigated. Particularly, during the direct transmission phase, base stations send their superposed messages to the near users and far users simultaneously according to a NOMA principle, while the near users act as energy harvesting enabled relays employing a power splitting protocol. During the cooperative phase, the near users transmit their decoded messages to the corresponding far users using harvested energy. Using tools from stochastic geometry, we firstly calculate the signal to interference ratios of the users in each NOMA group including one near user and one far user. Then, the closed-form expressions of the coverage probability, ergodic rate, and energy efficiency are derived respectively. Numerical results validate the derived expressions and show that the energy harvesting enabled cooperative NOMA system in a multi-cell network can improve the coverage probability, ergodic rate, and energy efficiency compared to its counterpart OMA system.