NOMA cooperative VLC systems: design and performance analysis with OOK and L-PPM modulation

Visible light communication (VLC) allows white LEDs to communicate while lighting, which improves resource consumption. Multiple relay approaches can be employed in conjunction with cooperative communications to achieve large gains in spatial diversity, expand the coverage, and possibly boost system capacity. In this paper, the nonorthogonal multiple access (NOMA) cooperative techniques for VLC systems using on-off keying (OOK) and L-pulse-position modulation (L-PPM) are proposed. The maximum ratio combining (MRC) schemes is adopted at the receiving node to combine the signals received from cooperative transmissions. Further, the decode-and-forward relaying protocol is considered for cooperation. The proposed system is analyzed for a multiuser scenario that is followed by a two- and three-user scenario for detailed analysis. This study calculates the bit error probability (BEP) of an OOK/L-PPM modulated NOMA cooperative VLC system under perfect and imperfect successive interference cancellation. Simulation results are presented to validate the produced analytical BEP results.