  Non-orthogonal multiple access (NOMA) has become a promising technology for
next-generation wireless communications systems due to its capability to
provide access for multiple users on the same resource. In this paper, we
consider an uplink power-domain NOMA system aided by a reconfigurable
intelligent surface (RIS) in the presence of a jammer that aims to maximize its
interference on the base station (BS) uplink receiver. We consider two kinds of
RISs, a regular RIS whose elements can only change the phase of the incoming
wave, and an RIS whose elements can also attenuate the incoming wave. Our aim
is to minimize the total power transmitted by the user terminals under
quality-of-service constraints by controlling both the propagation from the
users and the jammer to the BS with help of the RIS. The resulting objective
function and constraints are both non-linear and non-convex, so we address this
problem using numerical optimization. Our numerical results show that the RIS
can help to dramatically reduce the per user required transmit power in an
interference-limited scenario.
