Visible light communications: Toward multi-service waveforms

In visible light communications (VLC) systems based on baseband intensity modulation (IM), the modulating signals are designed for a single-purpose to either support single-user access using single-carrier pulsed modulation such as On-Off keying (OOK) or multi-user access mainly using the multi-carrier orthogonal frequency division multiplexing (OFDM). In VLC based sensing, transmitted sinusoidal beacons are considered to identify the different light sources. A key challenge is that such systems are not capable of supporting simultaneous bit streaming and sensing to high-end devices already equipped with chip sets compatible with OFDM and resource limited low-end devices for Internet-of-Things (IoT). In this paper, we present a novel design of a modulating waveform to effectively tackle this issue. The proposed waveform allows high-end and low-end devices to receive the same baseband signal, extract the useful part and process without any interference. We provide a detailed presentation of the design, explanation of the demodulation schemes and performance evaluation. We validated the performance through simulation results showing bit-error rate (BER) curves using multi-carrier OFDM for high-end devices. The bit-error performance is maintained at different dimming levels while offering a parallel data stream using single-carrier modulation for low-end devices and a stream of sinusoidal beacons needed for the sensing mission.