Hybrid Multiple-Access: Mode Selection, User Pairing and Resource Allocation

This paper proposes hybridization of non-orthogonal multiple-access (NOMA) and orthogonal multiple access (OMA) schemes for next-generation cellular networks. Two hybrid schemes that operate NOMA/OMA mode selection as well as channel and power allocation are proposed to improve the resource utilization and bandwidth-efficiency for network capacity maximization. The two proposed hybrid schemes are: (1) single-cell hybrid multiple-access (SC-HMA) and (2) multi-cell hybrid multiple-access (MC-HMA) schemes. The SC-HMA scheme determines the optimal NOMA/OMA mode and user pairs in each resource block by utilizing a capacity matrix representing the capacity outcomes of pairing all possible combinations of users. On the other hand, in the MC-HMA, the NOMA/OMA modes are categorized into intra-cell and inter-cell based on an interference map, where the principal objective is to determine the best mode of operation between the user pairs to improve the overall sum-rate and quality-of-service (QoS). The results show that the proposed HMA schemes provide superior overall network capacity compared to the benchmark schemes. In addition, the SC-HMA scheme outperforms the MC-HMA in terms of network capacity at the expense of higher computational complexity.