VLC frontends for IoT applications

The expected high number of devices in Internet of things (IoT) networks requires sustainable communication systems, with low power, low cost and small sized devices. The current technology relies on radio frequency (RF) communi-cations, where the spectrum is progressively being saturated. Alternatively, visible light communications (VLC) has been sug-gested as a complementary technology, mitigating some of the drawbacks of RF. This paper proposes circuit level solutions for VLC-based IoT systems using a hybrid multi-band carrierless amplitude and phase modulation (m-CAP)/quadrature amplitude modulation architecture, which is power efficient, simpler and low cost. Frequency and noise analysis are performed in the optical frontends and the analog demodulator. The proposed receiver is tested using a pre-modulated m-CAP signal with two waveforms as the carrier signal (sine and square). Although square waveforms may degrade demodulation performance, it simplifies the local oscillator, thus reducing the cost. Results show a successful demodulation of the original data, for both carrier types.