  This letter investigates the uplink outage performance of intelligent
reflecting surface (IRS)-assisted non-orthogonal multiple access (NOMA). We
consider the general case where all users have both direct and reflection
links, and all links undergo Nakagami-m fading. We approximate the received
powers of the NOMA users as Gamma random variables via moments matching. This
allows for tractable expressions of the outage under interference cancellation
(IC), while being flexible in modeling various propagation environments. Our
analysis shows that under certain conditions, the presence of an IRS might
degrade the performance of users that have dominant line-of-sight (LOS) to the
base station (BS), while users dominated by non-line-of-sight (NLOS) will
always benefit from it.
