  In this paper, we investigate the resource allocation for uplink
non-orthogonal multiple access (NOMA) enabled low-power wide-area (LPWA)
networks to support the massive connectivity of users/nodes. Here, LPWA nodes
communicate with a central gateway through resource blocks like channels,
transmission times, bandwidths, etc. The nodes sharing the same resource blocks
suffer from intra-cluster interference and possibly inter-cluster interference,
which makes current LPWA networks unable to support the massive connectivity.
Using the minimum transmission rate metric to highlight the interference
reduction that results from the addition of NOMA, and while assuring user
throughput fairness, we decompose the minimum rate maximization optimization
problem into three sub-problems. First, a low-complexity sub-optimal nodes
clustering scheme is proposed assigning nodes to channels based on their
normalized channel gains. Then, two types of transmission time allocation
algorithms are proposed that either assure fair or unfair transmission time
allocation between LPWA nodes sharing the same channel. For a given channel and
transmission time allocation, we further propose an optimal power allocation
scheme. Simulation evaluations demonstrate approximately 100dB improvement of
the selected metric for a single network with 4000 active nodes.
