On the outage performance of energy harvesting NOMA-based simultaneous cooperate and transmit IoT networks

In this paper, we consider a two-way network-coded relaying system consisting of two Primary Users (PUs) communicating via the relay node as the primary network with licensed spectrum. Multiple IoT devices capable of harvesting energy from a power beacon, utilize the same spectrum as Secondary Users (SUs). The SUs cooperate with the primary network and then transmit their own data. The devices harvest their required energy from a power beacon (PB), located near the primary relay node and store the energy in finite-size batteries. In phase one, the primary network communicate using the network coding technics and in the second phase, the SUs cooperate with the relay node by retransmitting the relay's data to PUs. In the last phase, SUs transmit their gathered information to a fusion center (FC). We apply TDMA and Signals Combining (SC) schemes in cooperation phase and derive the closed-form expressions for the outage sumrate of the secondary network. To increase the outage sumrate of the secondary network, a new NOMA-based simultaneous cooperate and transmit (NBSCT) scheme with a new time schedule is proposed. The corresponding expressions are derived and compared with that of the mentioned methods for various network parameters. The numerical results verifies that the outage sumrate of secondary network in proposed NBSCT scheme outperforms the TDMA and SC schemes under Rician fading and improves the outage sumrate by approximately 9.8%.