Implementation of 16 QAM signal transmission over RO-VLC system using high power LEDs

Abstract

White LEDs attract researchers for indoor visible light communication systems due to their good modulation characteristics, high efficiency, long lifetime, low cost, high tolerance to humidity, low power consumption, and minimal heat generation. Major challenges need to be resolved for LEDs including signal attenuation, ISI, and limited bandwidth for the proliferation of VLC systems. In this work, the challenges of signal attenuation and efficient utilization of limited bandwidth are addressed, keeping in mind the cost factor. A commercial high-power white phosphorous-coated LED with an optical preamplifier is used for a spectrally efficient 16 QAM Radio-Over-VLC link. The effect of varying the preamplifier gain on the system performance is investigated. Lower gain values limit the communication distance of the VLC system. A maximum transmission distance of 7 m considering a super-forward-error-correction (SFEC) limit of 1.863 × 10−2 could be achieved for a data rate of 0.5 Gbps. The transmission distance needs to be reduced to 6 m for a higher data rate of 0.6 Gbps with a resultant bit-error-ratio (BER) of 1.44 × 10−2 which is well within the SFEC limit. The achieved error vector magnitude (EVM), symbol error rate (SER), and Log bit-error-ratio (BER) metrics are used to characterize the VLC system performance.