Performance Analysis of NOMA-Based Slotted ALOHA for mMTC (Invited Paper)

We evaluate the performance of three slotted ALOHA schemes for mMTC; the simple slotted ALOHA without power control nor NOMA, the slotted ALOHA with power control for solving the near-far problem, and the slotted ALOHA with NOMA for increasing the performance gain. The numerical results reveal that the near-far problem impairs fairness in terms of the transmission success probability if the power control or NOMA is not applied. Application of the power control solves the near-far problem, but the performance of the slotted ALOHA largely degrades. Application of the NOMA to the slotted ALOHA may solve the near-far problem, but the unfairness due to the near-far problem arises again if the number of the target values for the received signal strength increases. These results indicate that there is an unavoidable trade-off between fairness and performance gain of the slotted ALOHA.