  The Internet of things (IoT), which is the network of physical devices
embedded with sensors, actuators, and connec- tivity, is being accelerated into
the mainstream by the emergence of 5G wireless networking. This paper presents
an uncoordinated non-orthogonal random access protocol, an enhancement to the
recently introduced Aloha-NOMA protocol, which provides high throughput, while
being matched to the low complexity requirements and the sporadic traffic
pattern of IoT devices. Under ideal conditions it has been shown that
Aloha-NOMA, using power-domain orthogonality, can significantly increase the
throughput using SIC (Successive Interference Cancellation) to enable correct
reception of multiple simultaneous transmitted signals. For this ideal
performance, the enhanced Aloha-NOMA receiver adaptively learns the number of
active devices (which is not known a priori) using a form of multi-hypothesis
testing. For small numbers of simultaneous transmissions, it is shown that
there can be substantial throughput gain of 6.9 dB relative to pure Aloha for
0.25 probability of transmission and up to 3 active transmitters.
