Joint Spectrum and Power Allocation for NOMA Enhanced Relaying Networks

In this paper, we investigate the joint resource allocation for the non-orthogonal multiple access (NOMA)-enhanced relaying networks involving the subcarrier pair, subcarrier-user assignment, as well as power allocation. In the NOMA-enhanced relaying networks, the relay is capable of communicating with multiple users on one subcarrier using the NOMA technology. To maximize the system throughput, the joint resource allocation problem is formulated as a mixed-integer nonlinear programming problem, which is difficult to tackle in general. Furthermore, there is strong coupling between the subcarrier-user assignment and the power allocation due to the multi-user interference in the NOMA system. To reduce the complexity, we separate the joint resource allocation problem as two subproblems in terms of the subcarrier assignment (subcarrier pair and subcarrier-user assignment) and power allocation, respectively. In particular, we propose a subcarrier assignment scheme based on the simulated annealing algorithm to optimize the subcarrier pair and subcarrier-user assignment with the fixed power allocation. Then, the power allocation problem is transformed as a difference of convex functions programming problem, and the sequence convex programming method is adopted to solve it. The simulation results illustrate that the proposed algorithm can effectively improve the system throughput.