Unified Multi-User Multiplexing Scheme With Enhanced NOMA (eNOMA) for HAPS

To provide extreme coverage towards 5G Evolution and 6G, high altitude platform station (HAPS) is an important component in non-terrestrial network (NTN) due to its deployment flexibility. Multi-beam transmission should be used in HAPS for high throughput, where each beam covers one cell with multiple users. However, intra-beam and inter-beam interference will be severe with traditional multi-user multiplexing schemes, which may affect the HAPS performance. In this paper, an enhanced non-orthogonal multiple access (eNOMA) scheme is firstly proposed to overcome intra- and inter-beam interference. Then a unified multi-user multiplexing scheme is further proposed to dynamically adapt between spatial-division multiple access (SDMA), non-orthogonal multiple access (NOMA) and eNOMA for various interference scenarios. The evaluation results show that the proposed scheme achieves maximum 48% spectrum efficiency (SE) gain over existing schemes under three user configuration.