Spherical Code Superposition NOMA and Its User Pairing Strategy

A novel non-orthogonal multiple access (NOMA) scheme with spherical code superposition and its user pairing strategy are proposed. A transmitter transmits the superposition of the signals of two users, each of which is selected from the high dimensional spherical code on the same time-frequency resource by power-domain multiplexing NOMA. Upper bounds of the word error probabilities of the two users are derived. Based on them, a power allocation scheme for the two users is proposed, which guarantees that their word error probabilities are below a certain threshold. Under our power allocation scheme, the optimal user pairing strategy that minimizes the total power consumption in a general multi-user system is analytically found. Numerical results show that our proposed system outperforms some benchmark methods.