  Non-orthogonal multiple access (NOMA) is a technology enabler for the fifth
generation and beyond networks, which has shown a great flexibility such that
it can be readily integrated with other wireless technologies. In this paper,
we investigate the interplay between NOMA and generalized space shift keying
(GSSK) in a hybrid NOMA-GSSK (N-GSSK) network. Specifically, we provide a
comprehensive analytical framework and propose a novel suboptimal energy-based
maximum likelihood (ML) detector for the N-GSSK scheme. The proposed ML decoder
exploits the energy of the received signals in order to estimate the active
antenna indices. Its performance is investigated in terms of pairwise error
probability, bit error rate union bound, and achievable rate. Finally, we
establish the validity of our analysis through Monte-Carlo simulations and
demonstrate that N-GSSK outperforms conventional NOMA and GSSK, particularly in
terms of spectral efficiency.
