  With the exponential increase of the number of devices in the communication
ecosystem toward the upcoming sixth generation (6G) of wireless networks, more
enabling technologies and potential wireless architectures are necessary to
fulfill the networking requirements of high throughput, massive connectivity,
ultra reliability, and heterogeneous quality of service (QoS). In this work, we
consider an uplink network consisting of a primary user (PU) and a secondary
user (SU) and, by integrating the concept of cognitive radio and multiple
access, two protocols based on rate-splitting multiple access and
non-orthogonal multiple access with successive interference cancellation are
investigated in terms of ergodic rate. The considered protocols aim to serve
the SU in a resource block which is originally allocated solely for the PU
without negatively affecting the QoS of the PU. We extract the ergodic rate of
the SU considering a specific QoS for the PU for the two protocols. In the
numerical results, we validate the theoretical analysis and illustrate the
superiority of the considered protocols over two benchmark schemes.
