repetition slotted ALOHA (IRSA). Specifically, packet replicas are transmitted with discrete
power levels, which are pre-determined by the NOMA scheme. In this case, most packet
collisions can be resolved in the power domain, contributing to a much lower packet loss
rate. Density evolution analysis is formulated and the degree distributions are optimized for
different numbers of power levels. The simulation results validate our analysis and show that …