Performance of Cooperative NOMA Communications in Mixed Fading Channels

User cooperation in non-orthogonal multiple access (NOMA) is recognized to substantially enhance spectrum efficiency in dynamic resource-constrained systems. This paper examines the end-to-end performance of a two-stage cooperative NOMA network with decode-and-forward relaying over mixed fading channels. The source to the cell-center user and the cell-center user to edge-user links undergo either Rician or Rayleigh fading. Based on the signal-to-noise ratio (SNR) obtained, we derive the closed-form expression for the system's outage probability and the average error probability (BEP) of M-ary quadrature amplitude modulations for the mixed fading conditions. The simulation results demonstrate the Rician Kfactor's significance and enhanced system performance in a Rician/Rayleigh compared to a Rayleigh/Rician fading channel.