Experimental validation of analog m-CAP receivers for Internet of Things

Abstract

In the framework of future Internet of Things (IoT) systems, the number of connected devices is increasing, along with the requirement of environmentally friendly devices, which should have low power/cost/size features. Visible light communications (VLC) has been proposed as a complementary technology for a vast number of scenarios, in particular for IoT, where it can favour device density growth by enabling spectrum reuse within few meters. This paper presents a VLC-based communication system, using analog demodulation for multi-band carrierless amplitude and phase (m-CAP) modulated systems in IoT multi-user scenarios. The goal is to implement and validate an IoT system architecture where multiple simple and low cost/power receivers can receive and decode narrow-band information sent by a single and complex broadband transmitter, located at lighting fixtures. An experimental testbed is developed for the proposed system to evaluate its performance in terms of eye patterns, constellations, error vector magnitude, and bit error rate (BER) for two line-of-sight scenarios. The results show that the system is tolerant up to 2.5 m, achieving a BER lower than the forward error correction (FEC) limit. Moreover, it allows the device to be tilted up to 45° and still achieve a BER below the FEC limit, for distances below 1.7 m.