  Large intelligent surface (LIS) has recently emerged as a potential enabling
technology for 6G networks, offering extended coverage and enhanced energy and
spectral efficiency. In this work, motivated by its promising potentials, we
investigate the error rate performance of LIS-assisted non-orthogonal multiple
access (NOMA) networks. Specifically, we consider a downlink NOMA system, in
which data transmission between a base station (BS) and $L$ NOMA users is
assisted by an LIS comprising $M$ reflective elements. First, we derive the
probability density function of the end-to-end wireless fading channels between
the BS and NOMA users. Then, by leveraging the obtained results, we derive an
approximate expression for the pairwise error probability (PEP) of NOMA users
under the assumption of imperfect successive interference cancellation.
Furthermore, accurate expressions for the PEP for $M = 1$ and large $M$ values
($M > 10$) are presented in closed-form. To gain further insights into the
system performance, an asymptotic expression for the PEP in high
signal-to-noise ratio regime, the achievable diversity order, and a tight union
bound on the bit error rate are provided. Finally, numerical and simulation
results are presented to validate the derived mathematical results.
