A Low-Cost Visible-Light-Communication-Enhancing Downlink Relay for Future Ultra-Massive IoT Networks

In this paper, a novel low-cost relay system is designed and validated for existing Visible-Light-Communication (VLC) indoor downlinks to improve the competitiveness in future cost-sensitive ultra-massive Internet of Things (IoT) networks. The proposed VLC relay system transmits its local information while rebroadcasting the base-station signal without any sampling or complex signal processing device. This provides a low-cost approach to extend the coverage of VLC while supporting services beyond the data transmission of the VLC system. The feasibility of the proposed VLC relay is validated, and its performance is estimated in an indoor Orthogonal Frequency-Division Multiplexing (OFDM) VLC simulation environment. The coverage with Bit Error Rates (BER) of 10
⁻⁴
, 10
⁻³
, and 10
⁻²
is increased from 6.09% to 17.97%, from 9.27% to 30.04%, and from 13.15% to 40.18%, respectively, by employing the proposed VLC relay system. Meanwhile, the local information of the relay system consisting of the relative distance, the network registration, and the time delay information are successfully received by the user to assist the services beyond the data transmission.