Performance enhancement of outdoor visible-light communication system using selective combining receiver

New generation of high-intensity aluminium gallium arsenide (AlGaAs) and aluminium indium gallium phosphide (AlInGaP) light-emitting diodes (LEDs) which have permitted the replacement of incandescent-based traffic lights with LED-based traffic lights, unfolds the potential of implementing visible-light communication (VLC) system on outdoor environment. The feasibility of outdoor VLC system is undoubtedly questionable because of the significant ambient-light noise caused by daylight. Existing performance studies related to this system have not taken into account the effect of ambient-light noise which varies largely from day time to night time. The authors propose an analytical daylight noise model based on a modified Blackbody radiation model to capture the effect of ambient-light noise and conduct an in-depth study on the impact of daylight on the system performance. The proposed daylight noise model allows us to perform analytical analysis which produces relatively accurate results with less complexity, as compared to the existing time-consuming simulation. The authors also introduce a new receiver structure employing the selective combining technique to significantly reduce the effect of background noise. From numerical analysis, the authors show that the new receiver structure is able to achieve a signal-to-noise ratio (SNR) improvement of approximately 5 dB and establish a stable communication link at any time of the day.