Multi-band carrierless amplitude and phase modulation and subcarrier multiplexing (SCM) are combined to produce a novel multi-users access scheme for visible light communications (VLC). To demonstrate this scheme, an experimental and realistic scenario is setup by using a low-cost commercial office white light-emitting diode (LED) downlight. Furthermore, subcarrier spacings are added to reduce the inter-channel interferences and the parameters of the pulse shaping filters are optimized. The distance between the transmitter and the receiver is fixed at 2.15 m. After the optimization, the experiment setup achieves a spectral efficiency of 5.08 b/s/Hz after subcarrier spacing and with very light post-processing. A total of 20 users can be provided with the multi-users access scheme with a sum data rate of 162.5 Mb/s. The receiving attocell is measured at 4.56 m 2. To the best of our knowledge, the resulting work presents the highest range, and one of the highest spectral efficiencies for a phosphorous white LED (ph-LED)-based VLC system, thanks to subcarrier spacing. With SCM, it is also the first ph-LED-based VLC multi-users system.

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We want to allocate the users to the optimal subcarriers in visible light communication. Allocation algorithms adapted from fiber-optic and implemented in an experimental setup attain a deviation from the bit rate target inferior to 5 percent for 11 users.