Amplify-and-Forward Integration of Power Line and Visible Light Communications

This paper proposes a low-complexity scheme for the integration of power-line communication (PLC) and visible-light communication (VLC) systems. Rather than decoding the PLC signal prior to transmission from an LED luminary, a simple all-analog PLC/VLC amplify-and-forward (AF) module is described. The incoming PLC signals, which occupy a band of 2–28 MHz, are frequency down-shifted prior to transmission to increase the usable bandwidth of the LEDs. The required DC bias is then added to make the signals compatible with intensity modulation/direct detection (IM/DD). In addition to DC-biased optical OFDM (DCO-OFDM), spatial optical OFDM (SO-OFDM) is applied to PLC/VLC integration. In SO-OFDM, the LEDs are divided into groups, and each group of LEDs is modulated by a different filtered OFDM signal. The results show that frequency down-conversion of the PLC spectrum prior to forwarding provides an improvement in capacity, while SO-OFDM provides a peak-to-average power ratio (PAPR) reduction which translates into improved capacity when the VLC link is operating in the high signal-to-noise ratio (high-SNR) regime.