  We consider uplink power control in wireless communication when a large
number of users compete over the channel resources. The CDMA protocol, as a
supporting technology of 3G networks accommodating signal from different
sources over the code domain, represents the orthogonal multiple access (OMA)
techniques. With the development of 5G wireless networks, non-orthogonal
multiple access (NOMA) is introduced to improve the efficiency of channel
allocation. Our goal is to investigate whether the power-domain NOMA protocol
can introduce performance improvement when the users interact with each other
in a non-cooperative manner. It is compared with the CDMA protocol, where the
fierce competition among users jeopardizes the efficiency of channel usage. In
this work, we conduct analysis with an aggregative game model, and show the
existence and uniqueness of an equilibrium strategy. Next, we adopt the social
welfare of the population as the performance metric, which is the average
utility achieved by the user population. It is shown that under the
corresponding equilibrium strategies, NOMA outperforms CDMA by higher
efficiency of channel access for uplink communications.
