Message-Aware Uplink Transmit Power Level Partitioning for Non-Orthogonal Multiple Access (NOMA)

Abstract

In uplink non-orthogonal multiple access (NOMA), to accommodate the urgent and high-priority messages, different sets of transmit power levels can be used to transmit non-critical and high- priority messages. However, it is challenging to optimize the NOMA power level partitioning, when devices transmit their high-priority messages randomly, and the number of those devices is not known to the BS. Hence, in this paper, the problem of message-aware power level partitioning is studied for a wireless network with NOMA. This problem is posed as the problem of finding the minimum number of power levels used to transmit high- priority messages so that a minimum quality-of-service constraint is satisfied, even when the exact number of devices with high- priority messages is unknown. To solve this problem, the number of devices with high-priority messages is estimated by comparing the observed transmission failure frequency with the theoretical transmission failure probability in NOMA uplink. Then, the estimated number of devices with high-priority messages is used to derive the optimal partitioning of power levels. Simulation results show that the proposed algorithm improves the transmission success probability by 75% compared to the baseline case without optimal power level partitioning.