Performance Analysis for Downlink Relaying Aided Non-Orthogonal Multiple Access Networks With Imperfect CSI Over Nakagami-m Fading

Non-orthogonal multiple access ( NOMA) has been conceived as a breakthrough technology for the fifth generation (5G) wireless networks. With imperfect channel state information (ICSI) taken into account, we study an NOMA-based downlink amplify-and-forward (AF) relaying network under Nakagami-m fading in this paper. First, we investigate the system outage behavior, and close-form expressions for the exact and tight lower bounds of the outage probability are attained, respectively. By further evaluating the outage probability at the high SNR region, it is observed that an error floor exists in the outage probability due to the presence of ICSI. Finally, numerical results are presented to demonstrate the validity of our analysis and show the advantages of NOMA over conventional orthogonal multiple access. Moreover, simulation results verify that the optimal relay location for NOMA should be close to the source mode.