Joint Overlap Ratios and Power Allocation with User Fairness in Partial Non-Orthogonal Multiple Access (P-NOMA)

In power-domain non-orthogonal multiple access (NOMA), since many users are able to utilize a single frequency subcarrier with different power levels, user interference occurs if successive interference cancellation (SIC) at the receiver is not performed perfectly. To reduce the amount of interference among all the users, recently an alternative approach called partial-NOMA (P-NOMA) was proposed. In this approach, the system allows partially overlapped bandwidth of the users and enables them to use NOMA in the overlapped region while the users in the non-overlapped bandwidth are arranged to utilize orthogonal multiple access (OMA). What should be the amount of overlap ratios (OR)s and the corresponding power levels still needs further research. In this paper, we propose an algorithm for joint allocation of ORs and power in P-NOMA system, which is based on gradient search, with the maximum sum-rate objective and user fairness constraint. Simulation results show that the proposed algorithm, which has lesser complexity than exhaustive search, obtains the optimum ORs and power allocation (PA) coefficient such that the maximum sum-rate of the P-NOMA is higher than that of the conventional NOMA while the target user fairness based on Jain's index is achieved.