  In this paper, the application of simultaneous wireless information and power
transfer (SWIPT) to non-orthogonal multiple access (NOMA) networks in which
users are spatially randomly located is investigated. A new cooperative SWIPT
NOMA protocol is proposed, in which near NOMA users that are close to the
source act as energy harvesting relays to help far NOMA users. Since the
locations of users have a significant impact on the performance, three user
selection schemes based on the user distances from the base station are
proposed. To characterize the performance of the proposed selection schemes,
closed-form expressions for the outage probability and system throughput are
derived. These analytical results demonstrate that the use of SWIPT will not
jeopardize the diversity gain compared to the conventional NOMA. The proposed
results confirm that the opportunistic use of node locations for user selection
can achieve low outage probability and deliver superior throughput in
comparison to the random selection scheme.
