Joint transmission scheme for two multicast groups based on NOMA

Abstract

Non-orthogonal Multiple Access(NOMA), as a key technology of spectral efficiency improvement in future 5G networks, has attracted a lot of attention. This paper proposes a joint transmission scheme for two multicast groups based on NOMA. Firstly, to guarantee rigorous channel difference to perform Serial Interference Cancellation(SIC), a Maximum and Minimum Group Method (MMGM) is proposed to divide each multicast group (MG) into three subgroups (the best, the middle and the worst subgroups), which makes the maximum and minimum of one MG's channel gains to be the other MG's two cutoff points. Secondly, according to the relationship between the two MGs' channel gains sets, two transmission modes are proposed. In different modes, BS respectively transmits to two different subgroup pairs (SPs) on the orthogonal frequency bands. In one mode, the one SP is consisted by a MG's best subgroup and the other MG's middle and worst subgroups. In the other mode, one MG's best and middle subgroups and the other MG's worst subgroup constitute the first SP. The second SP in each mode is made up of remaining subgroups. Finally, BS chooses the mode which can achieve higher spectral efficiency to complete data transmission with power domain superposition. Simulation results show that the scheme can improve spectral efficiency with higher average service ratio for users.