SM and NOMA Joint Assisted Indoor Multi-User VLC Downlink

In this paper, a novel spatial modulation (SM) assisted successive interference cancellation (SIC) free non-orthogonal multiple access (NOMA) scheme is proposed for indoor multi-user visible light communications (VLC) downlink. In the proposed scheme, all users are grouped according to channel gains. The data information of users in each group is then mapped to the spatial domain and constellation symbol domain according to their bit error rate requirements. In addition, due to the inherent sparsity of SM modulated signals, the compressed sensing (CS) sparse reconstruction algorithm is revoked for demodulating signals at the receiver. In this process, the information carried by the activated light emitting diode index is demodulated using the CS aided sparsity reconstruction algorithm, while the constellation symbol information is demodulated using the maximum likelihood (ML) algorithm. Additionally, by combining the greedy algorithm with the ML algorithm, a new method for sparse signal reconstruction detection is proposed. Compared with traditional NOMA technology, at the receiver side, both the error propagation caused by SIC and intra-group interference can be eliminated. Furthermore, the computational complexity of demodulation is reduced by utilizing the proposed joint signal detection procedure. The effectiveness of the proposed indoor multi-user SM NOMA VLC architecture is validated through Monte Carlo simulations.