  We propose a method that uses inaudible ultrasonic waves to address the issue
of uplink transmission in visible light communication. Our scheme, which
applies frequency-shift keying modulation and receive beamforming by a
microphone array, has been experimentally confirmed. This system has an
adjustable receiving direction to enhance the anti-interference ability of
uplink transmission, and it meets the asymmetric requirements of uplink and
downlink service bandwidth for Internet services.
