Reliable visibile light communication with dark light synchronization

摘要

LEDs that transmit or receive data in a VLC channel may create a flickering effect which is caused by the human eye being able to perceive the fluctuations of the light intensity in a LED. To prevent flickering such that the LED is perceived as being illuminated at a constant intensity, the LEDs may emit light based on a pattern of dark and energy slots. During the dark slots, the LEDs may be reversed bias to determine how much light is received. Based on comparing the light received, each VLC system may synchronize respective clocks such that the dark slots align. The VLC systems may then transmit a data frame preamble instructing the other VLC systems to cease synchronization and use the dark slots to receive the data from the data frame. While transmitting the data frame, the VLC systems may continue to use the energy slots to prevent flicker.

主权项

1. A method, comprising:
detecting, using a first visible light system, an amount of light received during first and second dark slots of a predefined synchronization pattern; comparing the amount of light received during the first dark slot to the amount of light received during the second dark slot; adjusting, based on the comparison, a clock in the first visible light system such that the first and second dark slots align with corresponding dark slots of a second visible light system, wherein the first and second visible light systems use the same synchronization pattern; emitting light from a light source of the first visible light system during an energy slot in the predefined synchronization pattern, wherein respective time periods of the first and second dark slots and energy slot are set to mitigate an ability of a human eye to detect a change from one of the first and second dark slots to the energy slot in the predefined synchronization pattern; and after adjusting the clock of the first visible light system, transmitting a predefined start frame delimiter (SFD) preamble, wherein the SFD preamble is configured to maintain the synchronization between the first and second visible light systems, wherein the second visible light system is configured to record the data received during the corresponding dark slots in a data window and evaluate the data window to determine if the first visible light system is transmitting the SFD preamble.