  Compressive random access (CRA) is a random access scheme that has been
considered for massive machine-type communication (MTC) with non-orthogonal
spreading sequences, where the notion of compressive sensing (CS) is used for
low-complexity detectors by exploiting the sparse device activity. In this
paper, we study the application of power-domain non-orthogonal multiple access
(NOMA) to CRA in order to improve the performance of CRA (or increase the
number of devices to be supported). We consider Gaussian spreading sequences
and derive design criteria through a large-system analysis to determine the
power levels for power-domain NOMA. From simulation results, we can confirm
that the number of incorrectly detected device activity can be reduced by
applying NOMA to CRA.
