Performance Evaluation of White LED-based OFDM-VLC Systems with Blue Filters: Experimental Study

This paper experimentally evaluates the performance of visible light communications (VLC) systems employing phosphor-coated white light emitting diodes (LEDs). Phosphor-coated white LEDs though widely used commercially, are known to limit the system's maximum data rate. Such a limitation is conventionally treated by two methods: either adding a blue filter at the receiver or using orthogonal frequency multiplexing (OFDM) digital modulation technique. Adding a blue filter at the receiver is controversial in current literature and claimed to decrease the signal-to-noise-ratio (SNR) or to be inefficient if OFDM is employed. Hence, in this work, we experimentally evaluate the above OFDM based VLC system with and without a blue filter. Results are compared to prove that adding a blue filter at the receiver boosts SNR and bit-error-rate (BER) values. This, in turn, helps maximize the data rates supported by such systems. The addition of a blue filter is tested with different modulation techniques. Results in this work remove the controversy around employing a blue filter in OFDM based VLC systems with phosphor-coated white LEDs. Improved BERs and SNRs at high data rates are observed. Specifically, this experimental work demonstrates a BER enhancement of ∼40% and ∼15% for data rates up to 12 Mbps when a blue filter is added.