  This paper proposes a new medium access control (MAC) protocol for Internet
of Things (IoT) applications incorporating pure ALOHA with power domain
non-orthogonal multiple access (NOMA) in which the number of transmitters are
not known as a priori information and estimated with multi-hypothesis testing.
The proposed protocol referred to as ALOHA-NOMA is not only scalable, energy
efficient and matched to the low complexity requirements of IoT devices, but it
also significantly increases the throughput. Specifically, throughput is
increased to 1.27 with ALOHA-NOMA when 5 users can be separated via a SIC
(Successive Interference Cancellation) receiver in comparison to the classical
result of 0.18 in pure ALOHA. The results further show that there is a greater
than linear increase in throughput as the number of active IoT devices
increases.
