Throughput Maximization of Hybrid NOMA-FDMA-TDMA

Hybrid non-orthogonal multiple access (NOMA) has been widely explored to enhance system performance by integrating NOMA with frequency-division multiple access (FDMA) or time-division multiple access (TDMA). In this paper, we propose a new hybrid NOMA-FDMA-TDMA scheme that incorporates both FDMA and TDMA into NOMA. We jointly optimize the user pairing, channel allocation, time allocation, and power allocation to maximize the total system throughput, subject to the minimum throughput and transmit power constraints for each user. The resulting problem is a non-convex and mixed-integer nonlinear programming problem. To efficiently solve it, we first determine the maximum throughput for every feasible user pair, and then develop a low-complexity algorithm for optimal user pairing and channel allocation. Simulation results demonstrate that the proposed hybrid NOMA-FDMA-TDMA scheme significantly outperforms the existing hybrid NOMA-FDMA and hybrid NOMA-TDMA schemes.