In this work, we experimentally demonstrate a bi-directional transmission link using light emitting diode (LED) visible light communication (VLC) for both downlink and uplink paths. Time-division-duplex (TDD) is proposed and demonstrated to significantly eliminate the reflection interference in VLC. A free space bi-directional transmission of 2 m using simple on-off keying (OOK) modulation with bit error rate (BER) of < 10(-5) in both directions are achieved. Moreover, the influence of reflection interference is analyzed, showing the proposed scheme can significantly eliminate the reflection interference.
We propose and demonstrate using signal pre-distortion and equalization schemes for increasing the data rate of the white-light LED communication system. Bit-error-rate of <10 -10 at 10-Mb/s operation was achieve using 1-MHz bandwidth white-light LED.
Background optical noises generated by the conventional fluorescent light sources or AC-power light-emitting diode (LED) can significantly affect the performance of the LED optical wireless communication and produce challenges to implementation. We demonstrate using orthogonal frequency division multiplexing (OFDM) to effectively circumvent the optical background noises. Besides, by using simple equalization at the receiver side, the transmission capacity can be extended from 1 Mb/s to 12 Mb/s. The theory and analysis of the equalization are presented. Experiments at different data rates and different OFDM subcarriers are preformed, and results show that, by adjusting the number of OFDM subcarriers, the influence of the background optical noises can be significantly circumvented.
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