Indoor Fine Particulate Matter Monitoring in a Large Area Using Bidirectional Multi-hop VLC

These Particulate matter (PM) causes lethal diseases to humans, and both short term and long term exposure are known to have hazardous effects. PM10 and PM2.5 have diameters less 10 μm and 2.5 μm respectively, which makes them more dangerous to the human body. Thus, information regarding PM concentrations in indoor environments of dust sensitive places is essential for proper precaution. In this study, we measured PM values in a large area and transferred this information using visible light communication (VLC) to the monitoring node. VLC is considered as an efficient technique due to its unique advantages and is currently unregulated. We applied bidirectional VLC to transfer information to ensure two-way communication. We also applied a multi-hop strategy to make the system function as a query answering system at extended distances. At one end, we generated a request to relay the request to the proper node and received the response in the form of PM data. In our experiment, we implemented four nodes and conducted multi-hop communication utilizing only a VLC link. We achieved a distance of 13.5 m with a zero error rate between the two nodes using nonreturn to zero on-off keying (NRZ-OOK) modulation. In case of multi-hop, we achieved a distance greater than 40 m using four nodes to send dust information with a minimal error rate. This can be applied to large indoor areas where radio frequency is restricted.