Transmission Delay Minimization in Downlink NOMA Networks

This paper considers the problem of transmission delay minimization in downlink non-orthogonal multiple-access (NOMA) networks. Specifically, the goal is to minimize the maximum transmission delay over all network users via optimal power allocation, while ensuring the queue stability of the transmit buffer of each user. However, the transmission delay minimizing power allocation (TD-MIN-PA) problem happens to be non-convex (i.e. computationally-intensive). In turn, an optimal low-complexity solution procedure is proposed to minimize the maximum transmission delay. Simulation results are presented to evaluate the performance of the proposed solution procedure, which is shown to yield the optimal minimum transmission delay per user (and hence achieves delay fairness), in agreement with the TD-MIN-PA scheme (solved via a global optimization package), and superior to its OMA-based counterpart scheme; however, at lower computational-complexity.