Energy Efficient Non-Orthogonal Multiple Access for Machine-to-Machine Communications

This letter investigates an uplink energy minimization problem for machine-to-machine communications with non-orthogonal multiple access. To solve this non-convex problem, we first prove that transmitting with minimum rate and full time is optimal. Then, the original problem can be transformed into an equivalent convex problem, which can be effectively solved by the proposed optimal power control and time scheduling scheme. Numerical results show that the proposed scheme achieves the optimal energy consumption.