On the Performance of IRS-Aided NOMA in Interference-Limited Networks

This letter investigates the performance of intelligent reflecting surface (IRS) aided downlink power-domain non-orthogonal multiple access (NOMA) in Nakagami-
${m}$
fading channels with cochannel interference (CCI). Using the Gamma approximation, we derive closed-form expressions for the ergodic capacity and outage probability, while taking CCI into account. The analytical results, validated through Monte Carlo simulation, show that IRS-aided NOMA is superior to the IRS-OMA counterpart, and that the Gamma distribution closely approximates the cascaded Nakagami-
${m}$
distribution. The results are presented for various number of users and reflecting elements.