A suboptimal scheme for uplink NOMA in 5G systems

Non-orthogonal multiple access (NOMA) scheme is a key technique towards the 5th generation (5G) of wireless communication networks due to its higher spectral efficiency comparing to its orthogonal multiple access (OMA) counterpart. However, the complexity of conventional NOMA scheme is extremely high in massive-access scenes. In this paper, we propose a user-pairing based suboptimal scheme for uplink multiple-access by combining NOMA and OMA to facilitate the massive-access scenes. Furthermore, a user-pairing algorithm with O(nlogn) complexity is also derived. According to the Monte Carlo simulation, the proposed scheme shows only a little throughput loss comparing to the optimal transmission scheme in information-theoretic perspective.