LAUSR

We design a hybrid visible light (VL) and infrared (IR) data transmission scheme for indoor visible light communication (VLC) systems with multi-pulse position modulation (MPPM) dimming control. A low-power IR light-emitting diode is adopted to assist the VL downlink especially when the dimming level of VL is low. Both VL and IR orthogonal frequency division multiplexing signals are transmitted alternately during the “on” and “off” periods of MPPM dimming controlled pulses. In this way, MPPM “off” periods can be efficiently utilized to convey data information without affecting illumination level. This arrangement ensures reliable data transmission under all illumination conditions including dark scenario. Numerical results show that the additional IR link can always facilitate the use of low M-ary quadrature amplitude modulation (M-QAM) levels. The fluctuation of required M-QAM symbol rates caused by dimming control can also be mitigated. At low dimming levels, both the receiver sensitivity requirement for the VL link and the total required transmit power can be significantly alleviated while maintaining a constant data rate at BER < 10–3. Even with limited launching power, the proposed scheme can still extend dimming control range while achieving stable and reliable transmission quality effectively.