Spectral Optimization for Multi-carrier NOMA-Enabled Industrial Internet of Things

Non-orthogonal multiple access (NOMA) guarantees good spectral efficiency and better enhance system capacity. However, the deployment of NOMA is not easy due to complexity of resource management. This paper provides a new resource optimization architecture to improve the spectrum efficiency (SE) of the multi-carrier NOMA enabled Industrial Internet of Things (IIoT) network. Specifically, we jointly optimize carrier-user assignment and power control to maximize the SE of the system while satisfying the constraints on users quality of services (QoS) requirements, transmit power budget and successive interference cancellation. Since the optimization problem is a mixed integer non-convex programming problem, it is very difficult to solve. We decouple it into two sub-problems to solve. Sub-problem one: subcarrier-user assignment problem; Sub-problem two: power allocation to users on each subcarrier. Particularly, two subcarrier-user assignment algorithms (SUAA1 and SUAA2) are proposed to solve sub-problem one. In which SUAA1 is based on the traditional NOMA user pairing scheme, SUAA2 is based on strong users first. The sub-problem two is solved based on the Monotonic optimization method. The simulation results show that our resource management scheme has higher SE comparing with OMA scheme. Specifically, SUAA2 can improve the SE of the system while increasing the rate of far users comparing with SUAA1 and the random matching scheme under our power allocation algorithm.