Exact outage probability of two-way decode-and-forward NOMA scheme with digital network coding

In this paper, we propose a two-way decode and forward non-orthogonal multiple access (NOMA) scheme (called a TWNOMA protocol) in which an inter-mediate relay helps two source nodes to communicate with each other. In the proposed protocol, we implement digital network coding (DNC) to compress received data from these source nodes. We analyze and evaluate the system performance in terms of exact closed-form outage probability over Rayleigh fading channels. Simulation and analysis results discover contributions as follows. Firstly, the outage performance of the proposed protocol TWNOMA is improved when comparing with a conventional two-way scheme using DNC (called a TWDNC protocol), two-way scheme without using DNC (called a TWNDNC protocol) and two-way scheme in amplify-and-forward relay systems (called a TWANC protocol). Finally, the theoretical analyses are validated by performing Monte Carlo simulations.