On Outage Performance and Ergodic Capacity Analysis of Two User NOMA in a Cooperative Cognitive Radio Network With an Energy Harvesting Relay

In this paper, a dual-hop cooperative nonorthogonal multiple access (NOMA) scheme is investigated in which two independent sources communicate simultaneously with their respective destinations over Rayleigh fading channel sharing a common time switching relay (TSR)-based energy harvesting decode and forward (DF) relay in an underlay cognitive radio network (CRN). A TSR protocol is used at the relay for harvesting energy from the signals of the two sources. After successful decoding the symbols of the sources using successive interference cancellation (SIC), the relay transmits a superposition coded (SC) composite signal to the destinations following downlink NOMA where SIC is performed at the destinations. Novel analytical expressions on outage probability of each user pair, system outage probability, and ergodic capacity of each user pair are derived. The transmit power allocation of each source satisfying an outage constraint of PU is obtained by solving a transcendental equation. A statistical distribution of the power harvested at the relay from two independent sources is also presented. Impact of tolerable interference threshold at the PU receiver, constraint on PU outage is indicated on outage and ergodic capacity of users. Monte Carlo simulation is performed using a testbed developed in MATLAB, and simulation results agree well with analytical results.